GS.TS.NGND. O HNG CNGCHUYN tng hp hu c2011

CHNG I

CCH A NHM CHC VO PHN T CHT HU C V S CHUYN HO GIA CHNG

Qa trnh tng hp cc hp cht hu c thc cht l qu trnh chuyn ho t mt hp cht ny thnh mt hp cht khc di tc dng ca cc yu t nh cc tc nhn phn ng v iu kin phn ng. Qa trnh chuyn ho c th thchin c bng hai phng php c bn:

a mt nhm chc vo phn t ca hp cht hyrcacbon.

Chuyn ho tng h gia cc nhm chc vi nhau.1.1. A NHM CHC VO PHN T HYRCACBON

1.1.1. A NHM CHC VO ANKAN

a mt nhm chc vo phn t ca cc hp cht ankan c th s dng mt trong cc phn ng sau y tu thuc vo yu cu v mc ch ca s tng hp.

1.1.1.1. Phn ng halogen ho:

Phn ng xy ra theo c ch gc (SR) l thng to thnh hn hp nhiu sn phm khc nhau. Kh nng phn ng ca tc nhn halogen X2: Cl2 > Br2; cn kh nng phn ng ca nguyn t Hyr trong ankan l:

Bc ba > Bc hai > Bc mt > CH3 - H

1.1.1.2. Phn ng mtylen ho:

Phn ng mtylen ho cc hp cht ankan thng to ra mt hn hp cc sn phm khc nhau. Mt khc, phn ng loi ny c th xy ra theo 2 c ch:

1. C ch mtylen ho trc tip:

2. C ch tch - cng hp:

1.1.1.3.Phn ng nitr ho:

Phn ng thng c tin hnh trong tng kh nhit cao vi axit nitric hoc nit tetraoxyt lm tc nhn nitro ho

Phn ng xy ra thng km vi oxi ho ankan to thnh CO2 v H2O nn c hiu sut khng cao. Mt khc khi tin hnh phn ng nitr ho vi cc ng ng ca mtan thng xy ra s ct mch to thnh hn hp sn phm:

1.1.1.4. Phn ng synf ho

Phn ng ny c th c thc hin bng tc nhn sunf ho l axit sunfuric c:

Tuy nhin phn ng ny t hiu sut rt thp nn trong thc t thng s dng phn ng thay th hyr bng gc SO2Cl to thnh ankynlsunfclorua nh sau:

1.1.1.5. Phn ng xy ho:

Di nhng iu kin c bit, ankan c th b xy ho hp cht C H v chuyn v cc hp cht hyrxi hoc cc hp cht cacbonyl.

V d:

1.1.2. A NHM CHC VO ANKEN:

Vic a mt nhm chc vo phn t anken c th thc hin c bng phn ng cng hp electrophin, cng hp raddical phn ng thay th v oxy ho. Di y l s ca mt phn ng c bn thng c s dng trong tng hp cc hp cht hu c.

1.1.2.1. Phn ng cng hp:

Trong XY = H2, Br2, HCl, HBr, HI, H2SO4, HOH, HOCl...

Cc phn ng xy ra c th c s tham gia ca cc xc tc thch hp cng c khi khng cn s c mt ca xc tc. Trong i a s cc trng hp, phn ng cng hp cn xy ra theo quy tc Macpnhicp: Phn ng cng hp xy ra theo c ch gc (khi c s tham gia ca cc cht xc tc c kh nng to thnh gc t do nh poxit, peaxit...) th hng ca phn ng ngc vi quy tc Macpnhicp.

Cc phn ng cng hp ca mt s hp cht anken ri hyrcacbon hoc mtylen s cho sn phm ankyl ho:

Phn ng thay th nguyn t hyr v tr allyl ca cc hp cht anken c thc hin nhit cao (khong 6000C) vi cc tc nhn l clo Brm hoc N brmxucximit:

V d:

1.1.2.3. Phn ng oxi ho:

Phn ng oxy ho cc hp cht lephin thng to thnh cc sn phm cha xy l ancol hoc anhyt tu thuc vo tc nhn xy ha. V d nu xy ho cc hp cht lephin bng tc nhn KMnO4 lnh v long hoc dung dch peaxit HCOOOH th s thu c hp cht glycol nh sau:

Mt khc s khc nhau gia cc phn ng xy ho ca 2 tc nhn ny l vic to thnh cc sn phm ng phn hnh hc khc nhau. Phn ng xy ho bng KMnO4 thng to ra cc sn phm ng phn Cis tri li HCOOOH to ra cc sn phm ng phn trans.

Nu tin hnh phn ng xy ho bng tc nhn l hp cht zn th sn phm thu c l cc anhyt hoc xtn:

V d:

Phn ng ny thng c s dng xc nh cu to ca phn t olephin.

1.1.3. a nhm chc vo phn t ankin:

Tng t nh cc phng php a mt nhm chc vo hp cht anken, vic a mt nhm chc vo phn t ankin cng c tin hnh bng phng php cng hp hoc thay th nguyn t hyrlinh ng ca ankin.

1.1.3.1. Phn ng cng hp:

Trong : YZ = H2,Cl2, Br2, HCl, HI, H2O

Cc phn ng xy ra theo hng c th v mt lp th tu thuc vo vic s dng cc hp cht xc tc.

V d:

Phn ng cng hp vi nc thng xy ra vi s c mt ca xc tc l mi thu phn trong mi trng axit v to thnh sn phm l cc hp cht xtn:

V d:

1.1.3.2. Phn ng ankyl ho:Nguyn t hyr thuc lin kt ni ba ca ankin rt linh ng dn n cc hp cht ankin c tnh axit yu. V vy n c kh nng tham gia vi cc phn ng vi cc kim loi kim hoc vi cc ion kim loi nng.

V d:

Trong :

Hoc: Nu cho hp cht axetylua kim loi trn y tc dng vi cc dn xut halogen th s thu c cc sn phm ankyl ho:

1.1.4. a mt nhm chc vo phn t hp cht thm

Vic a mt nhm chc vo nhn thm ca cc hp cht hyddrrocacbon thm c thc hin bi cc phn ng xy ra theo c ch th electrophin (SE). Di y l s ca mt s phn ng c bn thng gp:

a, Nitrr ho:

b, Sunf ho:

c, Halogen ho

d, Ankyl ho theo Frien Craf:

d, Ankyl ho theo Frien Craf:

e, Nitrrz ho:

g, Az ho:

h, Phn ng Konbe:

i, Phn ng Raim Timan:

Trong bng s ca cc phn ng trn y, cc phn ng e v g ch xy ra i vi cc hp cht hyrocacbon thm hot ng mnh, cn cc phn ng h v i ch c ngha khi hp cht hyrocacbon thm tham gia vo phn ng l phenol.

Vic a mt nhm chc th hai vo nhn thm ca hyrocacbon thm c tun theo mt s quy lut nh hng nht nh. Ngi ta chia cc nhm th thnh 2 loi:

Loi I: Cc nhm tng hot (c kh nng lm tng mt in t ca nhn thm) - nh hng oct v para.

Loi II: Cc nhm gim hot (nhm ko in t ca nhn thm) - nh hng mta.

Kh nng hot ng ca cc nhm th trong phn ng th electrophin rt khc nhau v c sp xp theo th t nh sau:

NHM TH LOI I NHM TH LOI II

Tng hot mnhnh hng mta

- NH2 (-NHR, -NH2)- NO2- OH- N(+) (CH3)2

Tng hot va- CN

- OCH3 (-OC2H5...)- COOH (COOR)

- NHCOCH3- SO3H

Tng hot yu- CHO, COR

- C6H5nh hng Oct, para

- CH3 (-C2H5,...)- F, - Cl, - Br, - I

Vic a nhm chc th ba vo nhn thm khi c mt ca 2 nhm th s lm phc tp s nh hng ca phn ng th electrophin. V vy ta c th phn thnh cc trng hp sau:

1. Nu hai nhm th cng nh hng vo mt v tr th s nh hng s xy ra theo chiu ca cc mi tn sau:

2. Nu hai nhm th nh hng khc nhau th s theo quy tc:

nh hng ca nhm hot ho mnh (tng hoc gim hot) s quyt nh hng ca phn ng SE so vi nhm hot ho yu.

nh hng ca nhm tng hot s quyt nh hng ca nhm phn ng SE so vi nhm gim hot. S nh hng ny c thay i theo dy sp xp sau:

NH2 > - OH > - OCH3 > - NHCOCH3 > - C6H5 > - CH3> Nhm nh hng mta

V d:

1.1.5. A MT NHM CHC VO PHN T D VNG THM N GIN Vic a mt nhm chc vo nhn thm d vng n gin c thc hin bng phn ng th eleectrophin. Cc phn ng th xy ra cc hp cht furan, tiophen, pirol u tin nh hng vo v tr s 2.

V d:

Tng t nh vic a mt nhm th vo hp cht d vng 5 cnh, vic a mt nhm chc vo hp cht d vng 6 cnh cng c th thc hin bng phn ng th electrophin. Trng hp ny hng th u tin vo v tr 3 (hoc )

Phn ng th nuclphin ca hp cht piriin s cho ra cc sn phm th vo v tr 2 hoc:

1.2. S CHUYN HO TNG H GIA CC NHM CHC

1.2.1. CHUYN HO NHM CHC HYRXYL CA ANOL V PHENOL

S chuyn ho nhm hyrxyl ca cc hp cht ancol c th c thc hin bng mt s phn ng quan trng sau y:

a, Phn ng halogen ho:

Phn ng ny c th c thc hin bng cc tc nhn halogen ho nh hyrhalogenua HX, phtpho halogenua PX3, PX5, inyl clorua SOCl2.

Phn ng vi hyrhalogenua:

Phn ng xy ra theo c ch th Nuclphin, trong kh nng phn ng ca HX gim dn theo dy: HI > HBr > HCl, cn kh nng phn ng ca ROH thay i theo dy:

Allyl benzyl > bc ba > bc hai > bc mt

Nhiu khi phn ng xy ra vi s chuyn v. V d:

Hoc:

* Phn ng photpho halogennua:

Trong : PXn = PBr, PL3, PCl5V d:

* Phn ng vi tioonyl clorua:

* Phn ng tch loi hyrt ho:

Phn ng tch loi ancol xy ra theo c ch E1 v E2 vi s tham gia ca cht xc tc l axit. Kh nng tham gia phn ng tch loi ca ancol bin i theo dy:

ROH: bc ba > bc hai > bc mt

Hng ca phn ng tch loi xy ra sao cho to thnh anken l bn vng nht. Ngoi ra, phn ng tch loi cc ancol nhiu khi xy ra vi s chuyn v.

V d:

c, Phn ng oxy ho:

Phn ng chuyn ho nhm hyrxyl ca hp cht ancol bng phng php xy ho to thnh cc sn phm khc nhau tu thuc vo loi ancol v tc nhn, iu kin cc phn ng. Di y l s c bn ca mt s phn ng:

Bc mt:

Bc hai:

Bc ba:

1.2.2. CHUYN HO NHM AMIN

Tng t nh amnic, nguyn t nit trong nhm amni mang cp in t khng phn chia to nn kh nng tham gia cc phn ng nuclphin ca nhm chc ny. Sau y l s ca mt s phn ng chuyn ho c bn:

a, Phn ng to mui:

V d:

c, Phn ng to thnh amit:

* Bc mt

* Bc hai:

* Bc ba:

V d:

d, Phn ng vi axit nit:

* Amin thm bc mt:

* Amin bo bc mt:

* Amin thm v bo bc hai:

* Amin thm bc ba:

* Amin bo bc ba:

e, Phn ng tch loi:

Phn ng tch loi cc hp cht amin to thnh cc anken ch c th thc hin c khi chuyn chng thnh ion amni bc bn. C 2 phn ng tch loi c bn sau y:

* Phn ng tch loi theo Hpman:

V d:

* Phn ng tch loi theo Kopu:

V d:

1.2.3. CHUYN HO NHM HALOGEN

a, Do c nhng cp in t t do trn cc ocbital ca cc nguyn t halogen nn cc hp cht halogen tham gia phn ng th nuclophin. Di y l s ca mt s phn ng th nuclophin thng xy ra:

Phn ng Sn phm

R: X + : Z( R : Z + : X-

R: X + : OH( R : OH + : Xancol

R: X + : H2O( R : OHancol

R: X + : OR( R : ORete

R: X + : C ( CR( R : C ( CRankin

R: X + : Na ( R( R : Rankan

R: X + : I( R : Iankyl iua

R: X + : CN( R : CNnitri

R: X + : ROO :( R : COOReste

R: X + : NH3( R : NH2amin bc nht

R: X + : NH2R( R : NHRamin bc hai

R: X + : NH2RR( R : NRRamin bc ba

R: X + : SH( R : SHTiol(mcaptai)

R: X + : SR( R : SRTiete(sunfir)

Phn ng th nuclphin xy ra theo c ch SN1 hoc SN2 tu thuc vo bn cht ho hc ca dn xut halogen. S ph thuc c hiu qua s bin i sau:

Mt khc, cn ch thm rng phn ng xy ra theo c ch SN1 thng km theo s chuyn v:

V d:

a, Phn ng tch loi:

Cc dn xut halogen khng ch c tham gia ch yu vo cc phn ng th nuclphin m cn tham gia cc phn ng tch loi, to thnh cc hp cht khng no:

Phn ng tch loi ca cc dn xut halogen xy ra theo c ch E1 v E2. Khi ny tham gia phn ng tch loi ca chng theo c ch E1 v E2 thay i nh sau:

Bc ba > Bc hai > Bc mt.

c, Phn ng kh

Phn ng kh cc dn xut halogen c th xy ra bng Hyr vi s tham gia ca cc xc tc kim loi cng c th bng Hyr mi sinh (kh ho hc):

* Kh xc tc:

* Kh ho hc:

V d:

1.2.4. CHUYN HO NHM ANHYT V XTN:

Ha hc ca cc hp cht anhyt v xtn c xc nh bi s c mt ca nhm cacbonyl > C = O. Chnh nhm ny l trung tm ca s tn cng nuclophin. V vy, phn ng chuyn ho c trng cho an hyt v xtn l phn ng cng hp nuclophin. Ngoi ra, anhyt v xtn cn tham gia mt s phn ng khc nh xi ho, kh ho, ngng t,... Sau y l s ca mt s phn ng c bn.

a, Phn ng xi ho:

* Anhyt:

V d:

* Mtyl xtn:

V d:

b, Phn ng th:

- Kh ho thnh ancol:

V d:

- Kh ho thnh hyrcacbon:

V d:

- Kh ho thnh pinacol:

V d:

Amin ho - kh ho:

V d:

Phn ng cng hp Grinha:

Phn ng xy ra theo c ch cng hp nuclphin AN : vi focmanhyt to thnh ancol bc mt, vi cc anhyt khc to thnh ancol bc hai, vi xtn s to thnh ancol bc ba.

V d:

d, Phn ng cng hp to thnh xianhyric:

V d:

e, Phn ng cng bisunfit:

V d:

g, Phn ng cng hp vi cc dn xut ca amnic.

V d:

h, Phn ng cng vi ancol to thnh hp cht axtal:

V d:

i, Phn ng Kaizar:

V d:

k, Phn ng ngng t:

1.2.5. CHUYN HO NHM AXIT CACBOXYLIC V DN XUT CA CHNG

Tnh cht ho hc ca axit cacboxylic c xc nh bi s c mt ca nhm cacbonxyl : - COOH. Nhm ny c cu to t nhm cacbonyl ( >C = O) v hyrxyl (OH), do phn ng chuyn ho nhm - COOH cng chnh l s chuyn ho ca hai nhm ny. Di y l s chuyn ho ca mt s phn ng c bn:

a, Phn ng chuyn ho thnh cc dn xut axit:

* Chuyn ho thnh cloranhyrat:

V d:

* Chuyn ha thnh este:

* Chuyn ho thnh amit:

b, Kh ho:

c, Phn ng th hin tnh axit to thnh mui:

h, Phn ng cacboxyl ho:

CHNG II:S PHN CT V TO THNH LIN KT CACBON CACBON

Trong cc qu trnh phn ng ho hc, lin kt C X gia cacbon v mt nguyn t X khc (C th l cacbon, xy, halogen...) trong phn t cht hu c c kh nng t ra theo 3 kiu khc nhau:

Trong kiu phn ct th nht to ra mt ion vi nguyn t cacbon thiu mt electrn v mang in dng. Ion ny c gi l cacbcation. Trong kiu phn ct th hai ion sinh ra mang in tch m gi l cacbanion. l hai kiu phn ct d ly. Cong kiu phn ct th ba phn ct ng ly, to ra gc t do vi in t t do nguyn t cacbon gi tt l gc cacb t do.

S phn ct nh trn c th xy ra c khng hoc c th xy ra theo kiu no, iu tu thuc ch yu vo cu trc ca phn t cha nhm C X v cc iu kin tin hnh phn ng. S kho st cc ion v gc t do ca cacbon c tm quan trng c bit trong vic tm hiu c ch cc phn ng hu c.

2.1.CACBCATION

Ccbcation l nhng cation m trung tm in dng l nguyn t caacbon. C nhiu loi cacbcation khc nhau:

Ccbcation c ba lin kt C(+) (ph bin nht). Th d (CH3)3C(+).

Ccbcation ch c hai lin kt C(+). Th d CH2 = CH(+). C6H5(+).

Ccbcation khng kinh in (nonlassical carboncation) hay l cacbcation cu ni. Trong in tich dng c gii to nh cc lin kt hoc v tr tng i xa nguyn t cacbon trung tm.

Ccbcation c s phi tr 5 (rt t gp). Th d: CH5(+). Trong phn ny ch yu cp n loi cacbcation th nht.

2.1.1. NHNG PHN NG TO THNH CACBCATION

2.1.1.1 Cc phn ng ct lin kt C X thnh cacbcation

a. Phn ct lin kt C Hal. Mun cho lin kt C Hal b phn ct d ly iu kin tt nht l Hal c kh nng ht electron mnh, cacbcation sinh ra c cu trc tng i bn v dung mi c kh nng ion ho cao. V d triphnylclomtan l mt cht rn kt tinh khng mu, khng tan trong nc v d tan trong C6H6 hoc CHCl3 cho dung dch khng mu v khng dn in do s phn ly:

L tt nhin cc ion sinh ra u b sonvat ha, trong cc dung mi nh nitrmtan, axtn... triphnylclomtan cng b phn ly nhng mc yu hn. V dung dch cacbcation dn in v c mu nn ngi ta c th dng cc phng php vt l kho st. Chng hn bng phng php quang ph ngi ta thit lp c rng 00c dung dch 0,1M (C6H5)3C-Cl trong SO2 lng c cha 3,2% dng ion cn dung dch 0,01M cha 21%.

Trng thi ca lin kt C-Hal c th thay i r rt khi c tc dng ca cc mui halgenua kim loi c kh nng to mui phc vi halgen trong C-Hal, nh: SnCl4, AlCl3, SbCl5, HgCl2... Th d:

Qa trnh phn ly trn c th xy ra ngay trong cc dung mi khng phn cc nh benzen, ttraclorua cacbon... ng ch l nhiu dn xut halgen, vi halgen nguyn t cacbon bt i, c th t raxemic ho trong dung mi c kh nng ion ha cao v qu trnh phn ly c tnh thun nghch.

Nu dn xut halgen khng t phn ly thnh cacbcation raxemic ho c th ngi ta c th nhng mui halogen kim loi nh ni trn. Hin tng raxemic ho y l c s ca mt phng php kho st qu trnh phn ly, c bit l qu trnh phn ly ca nhng cht c phn ly km.

b, Phn ct lin kt C-OH. Lin kt C-OH rt kh t phn ly thnh cacbcation v anion hyroxyl. Chng hn triphnylcation l mt cht khng mu v trung tnh, khng phn ly trong C6H6. Phn ly rt yu trong SO2 lng nhng trong axit sunfuric c hay axit fomic c phn ly mnh cho ta nhng dung dch mu vng da cam. Quang ph ca cc dung dch ny ging quang ph ca dung dch (C6H6)3C

V phn ng trn chuyn dung dch mt cht khng mu thnh dung dch cht c mu (hoc mu thm hn) do hin tng to mui cho nn ngi ta cho l mt v d ca hin tng halcrm (Hal-mui, rm-mu)

Cc ancolloaij bo bc cao th d (CH3)3COH cng c kh nng to ra ion cacbni trong axit sunfuric c. Th d trimtylcacbinol

c. Phn ct lin kt C-C. Lin kt C-C ni chung kh phn ly thnh ion. Tuy nhin nhng dn xut thm ca metan nh ttraphnylmtan, imtylphnylmtan,...trong axit sunfuric ddawcjlaij c th cho ta nhng dung dch c mu v c tnh hunh quang khi chiu tia t ngoi vo, do hin tng to thnh cacbocation.

So snh quang ph electron ca dung dch trimtylcacbinol v dung dch imtylphnylcacbinol trong H2SO4 c vi dung dch trimtylphnylmtan ngi ta i n kt lun rng trimtylphnylmtan b phn ct thnh cation tecbutyl.

d. Mt s hp cht khc nh este ca axit v c mnh ROSO2H, ROSO2Ar, hoc hp cht az trong nhng iu kin thch hp cng c th phn ly thnh cacbcation. Th d:

2.1.12. Cc phn ng cng vo ni i to thanh cacbcation

a. Cng prtn vo ni i ca anken: Khi c mt axit mnh alken c th cng hp prtn thnh cacbcation.

nu ion ny rt t bn n s chuyn ho ngay. V d:

chng minh rng qu thc cacbcation c sinh ra t ken ngi ta so snh ph electron ca 1,1- iphnyltylen v ca hai dung dch ny c ph kh kin rt ging nhau, iu chng t trong c hai dung dch u to ra cacbcation mtyliphnyl mtyl.

b. Cng prn vo nhm cabnyl:

Cc anhyt v xtn - cha no vi lin hp cao, c kh nng kt hp prtn to thnh cacbcation cha nhm hyrxy ngay nguyn t cacbon trung tm. Th d:

Phn ng trn l mt phn ng halcrm.

Trong s cc phn ng to thnh cacbcation chng ta cn phi k n cc qu trnh to thnh hp cht thm khng c vng bn nh ion triphnyl-xycclpropenili, ication ttraphenyl-xycclpropenili...

2.1.2.1. Cu trc khng gian:

V mt l thuyt ta c th cho rng cacbcation c cu trc phng tng t R3B hoc cu trc hnh thp tng t R3N.

gii quyt vn ny ta c th a vo s bin i nng sut quay cc ca dung dch hp cht c cacbon bt i kiu R1R2R3C Hal. Ta bit rng khi ho tan hp cht trn vo SO2 lng s xy ra qu trnh thun nghch.

Nu cacbcation c cu trc phng nh triankyl bo th trong qu trnh nghch Cl(-) c th tn cng nguyn t cacbon mang in dng t hai pha vi xc sut nh sau:

kt qu s to ra bin th raxemic, v R1R2R3C-Cl trong SO2 lng s b raxemic ho.

Ngc li nu ion c cu trc hnh thp nh R3N th trong qu trnh nghch Cl(-) ch c th tn cng t mt pha thi.

kt qu l cu hnh ca phn t phi c bo ton.

Thc t cho thy rng cc phn ly thnh cacbcation nh trn i vi hp cht cacbon bt i lun lun km theo s gim nng sut quay cc. D kin ny cng vi cc d kin thc nghim khc chng t rng cacbcation c cu trc phng hay gn nh phng. Thuyt c lng t cng cho kt qu tng t.

Trong trng hp cacbcation triarylmtyl ta hiu cu trc phng l ba trc xut pht t nguyn t cacbon mang in dng xuyn qua cc v tr 1,4 ca vng benzen u trn mt mt phng. Cn ba vng khng nht thit trn mt phng m b lch i trong khng gian (do nh hng khng gian) tng t nh ba cnh ca mt chic qut bn.

Trong cc cation xyclpropy ba lin kit C-C trn mt mt phng, cn vng xyclpropan to thnh mt phng khc nhau thng gc vi mt phng va ni v song song vi trc ca obitan p cn trng ca nguyn t C(+). Th d:

Cu trc phng l iu kin cn cho cacbcation tn ti . V th, khc vi triphnyclomtan, 1-brmtryptyxen (A) trong SO2 lng khng cho dung dch mu v cng khng dn in. Khc vi triphnylcacbinol, 1 hyrxytryptyxen (B) trong H2SO4 c cng khong cho dung dch mu. Nhng iu chng t chng rt kh to ra cacbcation hnh thp.

2.1.2.2. Cu trc tinh vi v bn vng tng i

bn tng i ca cc ion cacbni c lin quan cht ch ti s phn b in tch (cu trc tinh vi) trong ton b ion. in tch cng c gii to rng ra nhiu nguyn t trong ion th bn tng i cng cao.

Mun tng bn ca mt cacbcation c th a vo nguyn t cacbon mang in dng nhng nhm c hiu ng lin howph hoc lin hp dng:

V vy, trong dy cation ankyl cng nh trong dy cc cation arlmtyl, bc ca cation cng cao bn ca cation cng ln:

Dy th hai thng c bn tng i cao hn dy th nht v hiu ng +C ca nhm aryl mnh hn hiu ng +H ca nhm ankyl. Tng t nh vy, s c mt ca nhm viryl C (Cation alyl) lm cho bn ca cation tng ln r rt:

Kt qu tnh ton in tch dng theo cc phng php ho lng cng nh cc kt qu kho st bng cc phng php vt l xc nhn c s gii to in tch dng trong cacbcation lin hp trn. Th d theo phng php MO Hucken in tch dng mt s cacbcation c gii to nh sau:

Cc nhm th c hiu ng +C hay +H v tr para ca C6H5CH2 hoc v tr ca CH2 = CHCH2 lm cho bn tng ln; tri li cc nhm th c hiu ng -C hoc H nhng v tr lm chop bn gim i.

Trong nhng trng hp cacbtion khng kinh in, s d chng c bn tng i cao (So vi chng hn) v c s gii to electron ca lin kt C C hoc electron ca lin kt C = C khng v tr lin hp i vi obitan trng m v tr xa hn. Th d:

(Sinh ra t CH3 = CHCH2Cl

(Sinh ra t C6H5CH2CH2Br)

hoc t xicl-C6H5CH2Cl)

S xut hin tnh bn vng c bit ca cc cation thm (th d ion trpili) cng do s lin hp v cc c tnh khc ca vng thm gy nn.

2.2.CACBANION

Khc vi cacbcation c nguyn t cacbn thit th electron v mang in tch dng, cacbanion c mt cp electron d nguyn t cacbon v mang in tch m. Gia loi ion ny c s lin quan cht ch; v iu kin to thnh v tnh cht c nhng im tng t nhau hoc i lp nhau; v th khi kho st cacbanion cn lin h vi cacbcation.

2.2.1 S PHN LY LIN KT C X THNH CACBANION

2.2.1.1. iu kin thun li cho s phn ly lin kt C X thnh cacbanion.

Mun cho lin kt C X d b phn ct d ly thnh cacbanion iu kin tt nht l: a. Cp electron lin kt C X chuyn mnh v pha nguyn t cacbon, chng hn cc lin kt CK, CNa,... trong hp cht c kim; b. Cacbanion sinh ra c cu to tng i bn nh cac anion triarrylmtyl chng hn; c. Dung mi c dng c kh nng ion ho cao, thng amniac lng, ete,...

Triphnylclomtan ch d phn ly thnh cacbcation thi. Nhng nu ta chuyn nhng phn t ny thnh dn sut natri (C6H5)3CNa trong amnic lng chng li cho ta nhng dung dch dn in v c mu, do s to thnh cacbanion v ion kim loi.

Cacbanion ca nhng ankan n gin c trong cc hp cht c nguyn t nh cc hp cht ca liti, natri, magi...; do ni chung cc hp cht ny tham gia phn ng nh nhng cacbanion. Tuy vy, khng nn ngh rng cc hp cht y l nhng mui n gin kiu R- M+ v rng cc lin kt gia cacbon vi kim loi phn no mang tnh cht cng ho tr.

2.2.1.2. S phn ly lin kt C H v lc C H tng i:

Lin kt C H cng c th b phn ct d ly to thnh cacbanion nu nguyn t H c linh ng rt cao. Th d triphnylmtan thc t khng tc dng vi kim c nhng tri (p-nitrophnyl) mtan li tc dng c vi NaOH to ra dn xut natri d phn ly thnh cacbanion.

Qa trnh phn ly lin kt C H y chnh l qu trnh phn ly ca nhng axit cho nn ngi ta c th dng cc gi tr pKa lm mc o s phn ct d ly ny.

2.2.2 CU TRC V BN TNG I CA CACBANION

2.1.2.1. Cu trc khng gian:

Nhn vo cng thc ca cacbanion ta c th cho rng cc anion ny c cu trc mt phng nh cacbcation. Nhng cacbanion li c cp electron cn d, nn cng c th chop rng chng c cu trc hnh thp.

gii quyt vn cu trc khng gian ca cacbanion ngi ta c dng phng php o s bin i tnh quang hot ca hp cht c cacbon bt i trong qu trnh to thnh cacbanion. Tuy vy phng php ny gp nhiu kh khn cn bn. V th trong tng thi gian, tng ngi c nhng nhn nh khc nhau.

Hin nay ni chung ngi ta nht tr rng cacbanion c th c cu trc hnh thp hay cu trc gn nh thng tu theo bn cht ca cc nhm th nguyn t cacbon mang in tch m.

Nu gia nhm th v cp electron C(+) khng c s lin hp th cacbanion c cu trc hnh thp theo mt cn bng gia hai dng:

V th trong phn ng di y cu hnh ca phn t vn bo ton.

Tri li nu gia nhm th v cp electron C(-) c s lin hp cho anion tr v bn vng th anion c cu trc phng hay gn nh phng. V vy, ta thy trong qu trnh sau y c s raxmic ho:

2.2.2.2. Cu trc tinh vi v bn tng i

Gia cu trc tinh vi (s phn b mt electron) v bn tng i ca cacbanion cng c mi lin quan: in tch m hay l mt electron nguyn t cacbon trung tm cng c gii to rng bn ca cacbon cng cao. Nhng nhm th vi hiu ng C c kh nng gii to in tch m nh vy, chng hn tnh ton cho thy trong cc anion alyl v benzyl in tch m nguyn t cacbon trung tm ch bng khong n v in tch.

V th tluen c pKa (( 38) nh hn ca tan (( 58) , triphnylmtan c pKa cn nh hn na

(( 33). bn ca cc cacbanion nh C6H5 CH2(-), (C6H5)6C(-) s tng ln khi tng ln v tr para c nhm th gy hiu ng C ( th d NO2, CN...) ngc li s gim i khi c nhm th +C.

Nu nhng nhm th -C ni trc tip vi nguyn t ccbnion s tng ln r rt (biu hin pKa). Th d:

Trong nhng trng hp , in tch ca cacbanion phn b 2 nguyn t khc nhau. Th d:

Nhng nhm c hiu ng -1 hoc H ni vi C(-) cng lm tng mnh bn ca cacbanion. Th d: pKa(theo thang Xtrviz) ca CF3H : 28, (CF3)3CH : 11.

Cc anion vng thm nh C3H5(-), C6H52 ... c tnh bn cao l do s lin hp v cc c tnh khc ca hp cht thm.

2.3 PHN NG TO LIN KT CACBON CACBON VI S THAM GIA CA CACBCATION V CACBONANION:

2.3.1. PHN NG TO LIN KT CACBON CACBON CA CACBCATION

2.3.1.1. Phn ng ankyl ho:

a. Phn ng ankyl ho ca cacbcation to ra lin kt cacbon-cacbon l phn ng cng hp vi ankan. V d in hnh nht ca phn ng ny l s to thnh 2,2,4 trimtylpetan c dng lm nhin liu cho ng c t izbutan v izbutylen.

Sau phn ng li tip tc 2, 3; 2, 3...

b. Phn ng ankyl ha ca cacbcation xy ra cc hp cht thm theo c ch SE (phn ng Faiden-Crap). Trong phn ng ny thit lp nn mt lin kt cacbon-cacbon mi:

Bng phn ng ny c th iu ch c nhiu hp cht thm c mch nhnh khc nhau. V d:

2.3.1.2. Phn ng cng hp vo anken

y l phn ng cng hp to thnh mt caacbcation mi vi s hnh thnh lin kt cacbon-cacbon:

Phn ng ny c ngha quan trng trong qu trnh trng hp theo c ch cactionic. V d phn ng trng hp izbutylen trong axit xy ra nh sau:

Trong nhng iu kin xc nh di tc dng ca axit H2SO4 s xy ra phn ng ime ho:

2.3.1.3. Phn ng ngng t crtnic:

Hp cht cacbonyl trong mi trng axit b prtn ho to thnh cacbocation:

Cc hp cht tham gia phn ng ngng t crtnic to thnh lin kt cacbon cacbon mi:

2.3.2. PHN NG TO LIN KT CACBON CACBON CA CACBANION:

Cacbanion c to thnh bng s tch i nguyn t (- hyr ca cc hp cht cacbonyl. V vy cacbonion l mt baz mnh tham gia cc phn ng to lin kt cacbon-cacbon nh mt tc nhn nuclphin.

2.3.2.1. Phn ng cng hp nuclphin vo hp cht cacbonyl:

a. Phn ng ngng t anatol:

V d: Phn ng to thnh hp cht ( - hyrxibutandehyt t axxetanehyt xy ra theo s sau:

b. Phn ng ngng t peckin:

Phn ng ca anhyrit ca axit cacbonxylic vi cc anhyt thm to thnh mi lin kt cacbon-cacbon xy theo c ch cng hp nuclphin (phn ng Peckin).

Cc phn ng to lin kt cacbon cacbon xy ra theo c ch ny cn tm thy rt nhiu hp cht khc nhau nh cc hp cht c kim loi, phn ng Refocmatxki s c trnh by trong phn sau:

2.3.2.2. Phn ng th nuclephin nhm axyl

a. Phn ng ngng t claizen

y l phn ng to thnh lin kt cacbon cacbon hp cht ( -xtn. V d phn ng iu ch tyl axetaxtat xy ra nh sau:

bTng hp malnic:

Mt trong nhng phng php to lin kt cacboxylic c da trn c s ca hp cht etylmelonat gi l tng hp malnic. Trong phn ng ny nguyn t ( -hyr ca etylmalnat rt linh ng nn d dng b thay th bi cc ion natri to thnh cacbonion.

Cacbanion c to thnh rt d tham gia phn ng vi cc dn xut halogen to thnh cc sn phm khc nhau:

Cc este malnic d b thu phn trong mi trng axit v sau b cacboxyl ho bi nhit to ra cc axit monocacboxylic:

Theo nguyn tc ca phn ng trn y khng nhng c th tng hp c axit kiu R CH2COOH, R CHCOOH m cn tng hp c cc iaxit kiu HOOC (CH2)n COOH.

R

2.4. TO LIN KT CACBON CACBON BNG CC HP CHT C KIM:

2.4.1. PHN NG CA HP CHT GRINHA:

Khi cho Magi tc dng vi cc dung dch ca ankyl halogenua trong ityl ete khan (C2 H5 )2O

Th phn ng s xy ra rt mnh lit kt qu l Magi b ho tan v thu c mt dung dch mi. Dung dch gi l tc nhn Grinha. Tc nhn Grinha l mt hp cht hot ng rt mnh, n tc dng nhiu cc hp cht v c k c nc, xy, CO2 v vi mt s lng rt ln cc hp cht hu c. Mt trong nhng hng quan trng cu phn ng cc hp cht Magi l to ra cc mi lin kt cacbon cacbon.

2.4.1.1. Phn ng cng hp ca tc nhn Grinha:

Phn ng cng hp ca tc nhn Grinha vi cc hp cht Cacboxyl (anehyt v xtn). Cc este v cc dn xut ca tylenxit u cho ra sn phm l cc ancol vi s to thnh cc mi lin kt cacbon cacbon mi. Trong phng php ny sn phm ca loi ancol thu nhn c tu thuc vo c im ca cc tc nhn c cha xy c s dng.

a.Phn ng ca tc nhn Grinha vi cc hp cht cacboxyl: T Focmandhyt HCHO s to thnh ancol bc 1, t cc anhyt to thnh ancol bc 20, v t xtn s to thnh ancol bc 30.

Vic vn dng phng php tng hp ny thu nhn mt hp cht cn thit theo mun cn phi cn c vo cu to ca sn phm ancol. Mt nhm ankyl lin kt vi nguyn t cabon mang nhm - OH to thnh t phn t ca cc tc nhn Grinha, hai nhm cn li t hp cht cacbonyl, v d c th thu nhn hp cht 2 phnylhecxanol -2 bng 2 s phn ng sau:

Nh vy c th thu nhn 2-phnylhecxanol -2 t mt xtr thm vi tc nhn Grinha c 4 nguyn t cacbon (1) hoc t mt xtn bo vi tc nhn Grinha (2). Tuy nhin thc nghim cho thy rng trong trng hp c th ny th tin hnh iu ch 2 -phnylhecxal -2 theo s (1) l tt nht.

b. Phn ng cng hp ca tc nhn Grinha vi este l mt trong nhng phng php tt nht iu ch ancol bc 30. Phn ng xy ra theo hai giai on: Giai on 1 to ra hp cht xtn v giai on 2 l phn ng ca xtn vi tc nhn Grinha to ra ancol:

Nh vy ancol bc 30 c th thu nhn c t xtn hoc este bng phn ng cng hp vi tc nhn Grinha. Tuy nhin cc kt qu nghin cu cho thy phng php iu ch ancol bc 30 t este l tt nht. V d triphnycacbinol c th thu nhn bng phn ng ca phnylmagibromua vi este etylbenzoat hoc xtn benzphenon. C 2 qu trnh c th thc hin t axit benzic theo s sau:

R rng qua s cho ta thy rng phn ng chuyn ho axit benzic thnh triphnycacbinol bng tc nhn Grinha qua bc to thnh este xy ra n gin hn, t giai on hn.

c. Phn ng to thnh lin kt cacbon cacbon ca tc nhn Grinha vi xi tylen l mt phng php quan trng iu ch cc ancol bc 10. Phng php ny c u im ln so vi phn ng iu ch ancol bc 10bng focmanhyt s to ra c sn phm c mch di hn 2 nguyn t cacbon so vi gc ankyl hoc aryl ca tc nhn Grinha:

2.4.1.2. Phn ng ca cc nhn Grinha v phn t cacbon electrophin:

a. Phn ng vi cc dn xut Halogen:

V nguyn tc tc nhn Grinha c th tham gia phn ng vi cc dn xut halogen theo c ch SN2 to ra lin kt cacbon cacbon. y l mt trong nhng phng php thun tin nht iu ch hydrocacbon no bc bn:

Phn ng ny cng c th dng iu ch cc hyrcacbon khng no:

Phn ng ca tc nhn Grinha vi dn xut halogen ca axit cacboxylic s to thnh hp cht xtn. Trong thc t ngi ta c th li cho phn ng dng li giai on to ra xtn hoc i xa hn na to thnh amol bc 3.

b. Phn ng vi cc hp cht nitrin RC ( N

Nhm xian trong cc nitri R C ( N phn ng vi hp cht magi to thnh lin kt cacbon cacbon tng t nh nhm cacbonyl:

Sau nhm Imin b thu phn to thnh hp cht xtn:

Phn ng ny c th s dng iu ch cc xtn bo.

V d:

hoc cc xtn thm:

Trong R - gc bo hoc thm.

c. Phn ng ca hp cht magi vi cc hp cht ankel, xy ra theo c ch cng hp. So vi lin kt C = O th lin kt i C = C kh tham gia phn ng cng hp vi hp cht phi kim hn:

Trong khi :

Tuy nhin s cng hp vo lin kt i c th thc hin c khi lin kt c hot ho bng mt nhm ht in t:

V d:

2.4.2. PHN NG CC HP CHT C KIM VI CC PHN T CACBON ELETROPHIN.

2.5.2.1. Cc hp cht c Natri v c Liti:

Cc hp cht ankyl natri v ankyl liti c nhiu im ging vi tnh cht ca cc hp cht c magi nhng c kh nng phn ng cao hn. to thnh lin kt cacbon cacbon, cc hp cht ankyl natri v ankyl liti c s dng trong nhiu phn ng khc nhau. V d phn ng tng hp Vuyc iu ch cc hp cht ankhan xy ra theo s sau:

Trong phn ng ny cc ankyl halogenua c phn t lng cng cao thng cho hiu sut cao v phn ng thng c s dng iu ch cc hyrcacbon mch di:

Tuy nhin phn ng tng hp ny ch c ngha dng tng hp ankan i xng R R, cn i vi cc ankan bt i R Rs to ra mt hn hp nhiu sn phm.

Cc hp cht ankyl c liti c th tc dng vi nhng hp cht c ni i, ni i lin hp vi nhn thm v cc ien:

Cc ankan liti cng vo butaien -1,3 cc v tr 1,4 v 1,2 nhng nu tin hnh nhit cao th phn ng cng vo v tr 1,4 l thun li. Phn ng c s dng tng hp polibutanien c cu trc iu ho tp th lm cao su ging cao su t nhin.

Khc vi hp cht c magi, c km tham gia phn ng vi cc hp cht cacbonnyl to thnh ancol bc ba c phn nhnh cao. V d: trizpropylcacbinol c th c iu ch t izpropylxtn v izpropyl liti nh sau:

2.5.2.2. Hp cht c km, catmi:

Tng t nh hp cht c magi, c km tham gia phn ng vi cc hp cht cacbonyl to thnh cc ancol khc nhau tu thuc vo tc nhn cacbonyl tham gia phn ng: focmahyt ( ancol bc mt; anhyt ( ancol bc hai; xtn, clorua axit ( ancol bc ba.

iu ng lu l phn ng ca anhyt hoc xtn vi km v este ca cc axit ( - halogen th ta c ( - hyrxiaxit (phn ng Refocmatxki).

to mi lin kt cacbon cacbon c th sue dng phn ng ca hp cht c catmi vi hp cht clorua axit:

Khc vi phn ng ca hp cht c magi vi clorua axit l sau khi to ra sn phm xtn, hp cht magi tip tc tc dng vi hp cht ny to thnh ancol bc ba, trong khi hp cht c catmi c tnh hot ng ho hc yu hn nn sn phm thu c ch dng li hp cht xtn. Mt khc hp cht c catmi cng khng phn ng vi nhiu nhm chc khn nhau nh NO2 CN - , - COOR. V vy s c mt ca cc nhm chc khc trong phn t clorua axit s khng gy cn tr n phn ng tng hp xtn. V d:

CHNG 3PHNG PHP NG V M VNG3.1. PHNG PHP TO VNG ANKAN

Qa trnh thu nhn cc vng anken t cc hp cht hyrcacbon mch thng thng c thc hin qua 2 giai on phn ng:

a. Chuyn ho mt hp cht mch h thnh hp cht mch vng bng phn ng n vng.

b. Chuyn ho hp cht vng thu c thnh hp cht vng cn thit phi iu ch, v d chuyn ho xycloancol thnh xycloankan hoc xycloanken thnh xycloankan.3.1.1. ANKYL HO TRC TIP:

chuyn ho cc hp cht mch h thnh mch vng bng phng php ankyl ho trc tip th cc hp cht mch h cn phi cha 2 nhm chc nh halogen, ancol, cacboxyl... V d phn ng to cc hp cht vng nh c thc hin bng cc s sau y:

Trong phn ng ny n = 1,2,3,4,5, - tc l c th iu ch t xyclopropan n xyclohecxan. X v Y l cc nhm halogen, cacboxyl. Xc tc thng hay dng l kim loi kim hoc cc hn hp kim loi. V d xyclpropan c iu ch t 1,3 ibrompropan vi xc tc natri kim loi theo phn ng sau:

V thc cht y l phn ng ng vng ni phn t Vuyc nu phn ng ny c thc hin vi tc nhn tch loi l bt km trong ancol th s c hiu sut cao hn.

iu ch xyclobutn vi hiu sut cao konor dng phn ng ca 1,4 dibrombutan vi hn hp Liti trong dung mi khng phn cc tetrarydofuran:

Bng phng php tng t cng c th iu ch xyclopental t 1,5 dibrompentan vi hiu sut 75%.

Tuy nhin trng hp cc hp cht vng c th iu ch bng phng php Peckin vi cc tc nhn phn ng l mui natri ca este nalnia v dn xut halogen:

iu ch cc vng 5, 6 v cc hp cht a vng thng s dng phng php Piria nhit phn mui canxi ca iaxit cacboxylic.

Phn ng loi ny nu dng iu ch xyclopentanon v xyclohecxanon th c hiu sut cao cn vi cc vng c s nguyn t cacbon ln hn th c hiu sut rt thp. Phn ng ny cng khng s dng c iu ch cc hp cht 3 hoc 4 vng.

Phng php ngng t cc ieste v cc dn xut ca n cng thng c s dng iu ch cc hp cht vng - phn ng icmon:

Trong iu kin tng t nh vy s xy ra phn ng ngng t ca hp cht nitrin:

Phn ng ngng t este lin phn t cng c th s dng iu ch hp cht vng. V d phn ng ca ietylxalat vi este glutariat hoc ng ng axtn ca n s to ra cc vng xtn 5 cnh:

S ngng t ca 2 phn t este xuxinat s to thnh hp cht vng 6 cnh:

Phng php ankyl ho trc tip cng c th thc hin bng phn ng ng vng cc hp cht hyrcacbon c 5 nguyn t cacbon vi xc tc Platin nhit 3000C.

i vi cc khung hyr cacbon c ln hn 5 nguyn t cacbon th bc u s to thnh vng 6 cnh nhng tip sau c th b hyr ho thnh vng benzen nu nh vng khng c mt nguyn t cacbon bc 40.

S c mt ca nguyn t cacbon bc bn s cn tr qu trnh thm ho :

Phn ng ankyl ho thu nhn hp cht vng c quan st thy s chuyn ho ln nhau ca cc hp cht vng. Phn ng m rng vng c thc hin bng s tn cng ca mt nguyn t cacbon mch nhnh ca vng vo khung cacbon ca vng (s chuyn v):

V d:

Phn ng cng c th xy ra theo hng ngc li km theo s hp vng:

C ch chuyn ho ca qu trnh chuyn v trn y xy ra theo s sau:

S m vng:

S hp vng:

Cc phn ng ankyl ho khng nhng ch dng iu ch cc hp cht n vng m cc hp cht a vng khc nhau. V d s to thnh cc hp cht hai vng c th c thc hin theo cc phn ng sau:

a. Tng hp vuyc:

b. Tng hp bng s h tr ging ca tc nhn c magi:

c.Ngng t cc vng anhyt hoc xtn vi nhau:

d.Kh ho cc vng xtn:

e. Phn ng to thnh cc hp cht spiran:

3.2. PHN NG CNG HP:

3.2.1. PHN NG CNG HP INX AN

Cc hp cht cacbonyl khng no tham gia mt phn ng rt quan trng vi cc ien lin hp c gi l phn ng inx An. Sn phm ca phn ng ny l mt vng 6 cnh c hnh thnh do kt qu cc mi lin kt gia nguyn t cacbon ca ni i trong hp cht cacbonyl khng no. Duwowis y l mt s v d v phn ng cng hp inx An:

Thc nghim chng minh rng phn ng cng hp xy ra d dng nu Anken (thng gi l phn ienophin) c th bi mt hoc nhiu nhm ko electron mnh, th d nh COOH,

Trong bng sau y l mt s ienophin c kh nng phn ng cao.

MT S CHT IENPHIN HOT NG

TNCNG THC

Ttraxiantylen

Crlonanhyt

Axitxinamic (els v trans)

Anhirit malic

Dimtyl malic

1- Nitrpropen

Acrilnitrin

Acrlin

tyl acrital

N phnylmalimit

imtyl fumaral

-Nitrositren

Mt trong nhng u im ca phng php inx An l n xy ra rt c th v mt lp th.

ien phn ng cu dng s-eis ca cc ni i ca n, bi v ni i sn phm (mt vng su) phi c cu hnh cis.

Mt im ng ch na l cu hnh ca ien v ca cht ienphin vn gi nguyn sn phm. iu ddod c ngha l hai cht ny cng hp cis vi nhau. Chng hn butaien phn ng vi imtyleste ca axit fumaric hoc axit malic trong tluen v nhit 1550C cho imtyleste ca cc axit trans - hoc cis xyclhexen - 1 icacbxylic -4,5.

cc th d ny ta thy cu hnh ca cht ienphin c gi nguyn .

Ta cng cn k n mt c im na ca phn ng ix An l trong nhiu trng hp cc cht phn ng b nh hng v mt ho lp th. Th d phn ng cng anhirit vo xyclpentaien c th i theo hai con ng dn ti hai sn phm khc nhau.

Trong thc t thng hnh thnh ng phn en l sn phm ch yu duy nht.

Phn ng ix An c l xy ra theo mt c ch nhiu trung tm, trong hai lin kt mi gia ien v cht ienphin hnh thnh ng thi (Hoc hu nh ng thi). Mt tin trnh phn ng ng thi nh vt c nhng yu cu rt cao v mt lp th, cc i tng phn ng phi c sp xp sao cho hai lin kt c th hnh thnh cng mt lc, ph hp vi iu ny cc phn ng ix An thng c entropi hot ho m mnh (t -20 n -25 cal/. Mol).

Sn phm phn ng ca cc tng hp ien thng l cc cht trung gian cho nhiu tng hp hu c. Bixicl -[2,2,1] heptaien (2.5) (I) c tng hp t xyclpentaien v axtien vi hiu sut khong 65%. Cht ny phn ng vi hecxaclozxiclpentaien mt cch hu nh ton lng trong mt tng hp ien th hai thnh cht anrin II l mt loi thuc tr su c hiu lc:

Trong s cc sn phm cng hp ix An ca hecxaclopentaien cn c nhiu loi thuc tr su khc v mt s plime chu nhit.

Cc phn ng ix An l thun nghch. Ta c th s dng tnh cht ca phn ng vo trong tng hp v sau khi thc hin cc bin i cc sn phm cng hp ix An ta li c th tch chng ra thnh cc hp phn. Chng hn cht tianhirit ca axit malic cng hp vi butalien, sau sn phm c chuyn thnh dn xut ion III ri tch ra thnh cc hp phn.

Mc du ni chung cc ien lin hp tc dng vi cc cht ienphin v tr 1,1 cho cc hp cht vng su, ngi ta cng bit c mt s phn ng cng 1,2 cho cc hp cht vng 4. Rt c th bn cht ca cht ienphin l yu t qut nh vic cng hp theo 1,4 hoc 1,2. Chng hn mc du tylen cng hp 1,4 vi butadien, ttraflotyln li cng hp 1,2:

Trong khi ttrafltylen cng vo xyclpentaien cho mt hn hp cc sn phm cng hp ng vng 1,2 v 1,4.

3.2.2. PHN NG CNG HP CA CACBEN V NITREN VO ANKEN

L nhng hp cht ho hc hot ng rt mnh v trong cc phn ng vi cc hp cht anken chng s dng nhm mtylen: CH2 to thnh cc hp cht vng. Mtylen v dn xut mtylen tham gia phn ng cng hp vo ni i (- C = C -) theo s sau:

Loi phn ng ny cng c iaknp s dng iu chnh mt s dn xut ca axit cacbxylic:

Phn ng cng c th dng tng hp xyclbutan t Anken:

Mtylen v dn xut ca n c th tham gia phn ng cng hp vo h ni i ca bn:

Tng t nh vy clocacben tc dng vi benzen to thnh ion tripili theo s sau:

Cc hp cht cacben v iazmtan cng c th tham gia phn ng cng hp vo ni ba (Ch c phn ng vi dn xut ca axetylen, nhng khng phn ng vi axtylen) to thnh vng khng no.

V d:

Mtylen cng c th cng hp vo cc hp cht vng ete v m rng vng hn:

3.3. PHNG PHP TO VNG THM V D VNG

3.3.1. TNG HP BENZEN V DN XUT CA BENZEN

Benzen c th c tng hp bng phn ng trime ho hp cht axtylen:

Phn ng ny c nhiu nh ho hc nghin cu vi cc xc tc v iu kin phn ng khc nhau.

thu c benzen Zelinxki tin hnh phn ng trn than hot tnh nhit 450 5000C. Trong khi Repe s dng xc tc l icabony itriphenylphotphin Niken [ (C6H5)3P(2 Ni (Co)2 v thu c dn xut th 1, 3, 4 ca Benzen. Bng vic s dng xc tc l [ Al(C2H5)3 + TiCl4( Xigler thu nhn c cc dn xut th 1, 3, 5 ca benzen. Vi xc tc l CrCl3 Xeis iu ch c hp cht hecxaphnylbenzen t iphnylxtylen:

b. Hp cht axtn di tc dng ca axit sunfuric m c s to thnh 1, 3, 5 trimtylbenzen (mzitilen).

Phn ng cng xy ra tng t i vi cc xtn loi R-CO-CH3.

V d t axtphenon C6H5COCH3 c th iu ch 1, 3, 5 triphnylbenzen.

Loi phn ng ny cng c th s dng iu ch cc dn xut bn t cc hp cht anhyt c nhm mtyl linh ng:

c. Mt trong nhng phn ng c s dng rng ri iu ch benzen l phn ng thm ho cc hp cht parafin bng xc tc platin nhit ~3000C:

Phn ng ny c th thc hin bng xc tc [ Al2O3 + Cr2O3 ] nhit trn 4000C.

d. Cc hp cht benzen cng c th c iu ch bng phn ng ehyr ho xyclhecxan v xyclohecxaien vi xc tc platin nhit cao.

3.3.1.2. Tng hp cc d vng 5 cnh:

a. Phng php quan trng v chung nht dng tng hp cc hp cht d vng thm, 5 cnh c bt u bng 1,4 - dicacbonyl.

Cc hp cht d vng 5 cnh c th c thu nhn bng phn ng nhit phn (cacbonxyl ho) axit muxic nh sau:

Phn ng ny khng s dng iu ch tiphen c nhng tiphen c th c iu ch bng phn ng ca axit vi P2S3

c. chuyn ho ln nhau gia cc d vng thm v khng thm 5 cnh lurep s dng xc tc Al2O3 4000C cho cc phn ng xy ra theo s sau:

d. Phn ng cng hp 1, 3 vo h ni i v ni ba ca tc nhn loi iazo, axit nit, axit, oxit nitril, hp cht nitron... cho php thu nhn mt s lng rt ln cc hp cht d vng 5 cnh khc nhau di y l mt s v d:

e. Cc hp cht d vng 5 cnh cng c th c iu ch bng phn ng ca Shulte nh sau:

e. Ngoi cc phng php chung iu ch cc hp cht d vng 5 cnh trn y, ngi ta cn s dng nhng phng php tng hp cc hp cht ring bit.

V d:

1. Phn ng iu ch furan v dn xut furan:

1. Phn ng iu ch tiphen:

2. Phn ng iu ch diophen:

3. Phn ng iu ch pirol:

4. Phn ng iu ch indol:

3.3.2. TNG HP CC HP CHT D VNG 6 CNH:

a. Tng hp piriin:

Piriin c th thu nhn bng phn ng ca axetylen vi axianhyric (phn ng Betlo):

b. Cc dn xut ca Piriin c th iu ch bng phn ng ca anehyt RCH2CHO vi amniac khi c mt xc tc Al2O3 4000C nh sau:

Dn xut Piridin cng c th c iu ch bng phn ng ca cc ien vi ankylinitril:

3.4. PHN NG M VNG:

Phn ng m vng ca cc hp cht vng xy ra di tc dng ca cc tc nhn khc nhau theo nhng c ch khc nhau tu thuc vo cu trc ca vng. Di y l mt s phn ng m vng c bn thng gp.

3.4.1. M VNG BNG PHNG PHP KH HO

Do qu trnh to thnh hp cht vng, cc nguyn t cacbon b bin dng khi trng thi lai to tng ng cu mnh nn trong cc hp cht vng tn ti mt sc cng (Sc cng Baye, sc cng Fitze...). iu ny dn n cc hp cht vng tham gia mt s phn ng kh ho tng t nh cc hp cht hyrcacbon khng no.

V d: Xyclpropan tham gia phn ng hr ho vi s ph v vng lin kt cacbon cacbon nhit 800C.

Trong khi phn ng vi xiclbutan xy ra 1200C.

Phn ng cng xy ra tng t i vi cc dn xut ca Xyclpropan v xiclbutan nhnh tu thuc vo s c mt ca cc nhm chc khc nhau s thu c cc sn phm khc nhau. V d phn ng hyr ho izpropyl - xiclpropan v izpropenyl xiclpropan s to thnh cc sn phm khc nhau nh sau:

3.4.2. PHN NG CNG HP THEO C CH ELECTROPHIN:

Cc hp cht vng c th tham gia cc phn ng cng hp vi cc tc nhn electrophin vi s ph vng. Phn ng thng xy ra di tc dng ca cc hyrhalogenua.

V d: phn ng ca xiclpropan v xiclbutan vi HBr xy ra nh sau:

Phn ng cng xy ra tng t khi s dng tc nhn electrophin l H2SO4 hoc Brm.

Kt qu nghin cu cc phn ng m vng cho thy rng s c mt ca cc nhm th i in t ca vng nh COOH, - CHO... s lm cho phn ng ph vng xy ra kh khn. V d cc dn xut ankyl ho ca xiclpropan rt d dng phn ng vi axetat thu ngn:

c bit cc phn ng ca h lin hp vng vi ni i thng xy ra theo quy tc phn Macopnhicop:

3.4.3. PHN NG CNG HP THEO C CH NUCLEPHIN:

Phn ng cng hp dn n p v vng theo c ch nuclonphin xy ra ch yu cc vng xtn, lactn... V d phn ng cng hp ca xianat Kali vo vng lactn xy ra theo s sau:

y l phn ng rt quan trng dng iu ch axit cacboxylic. Phn ng Buton vi tc nhn Grinha to thnh cc hp cht xtancol:

3.4.4. PHN NG M VNG BNG MT S TC NHN KHC:

Cc hp cht vng khng no hoc xtn c th tham gia phn ng oxy ho dn n s ph vng. V d hp cht xiclohexen b ph v bi phn ng oxy ho bng zn theo s sau:

Phn ng xy ho cng xy ra tng t i vi hp cht Xibtn nh sau:

Mt s loi hp cht vng c th b ph v bi phn ng thu phn. V d hp cht caprolactam b thu phn thnh axit aminocapric nh sau:

Phn ng thu phn dn n s ph vng ca cc hp cht xtn cng c th xy ra di tc dng ca nh sng.

CHNG 4BO V NHM CHC TRONG TNG HP HU C

CHIN LC CHUNG:

Trong tng hp hu c nhiu trng hp ngi ta phi tin hnh bo v mt s nhm chc m nhng nhm nu trng thi t do th n c th tham gia vo mt s phn ng ho hc theo nhng hng khng cn thit. Phng php ny ngy cng c ng dng rng ri trong cng nghip sn xut ho cht nhm to ra nhiu loi sn phm cn thit vi cht lng tt.

Trong lch s pht trin ca nghnh ho hc hu c trc y, ngi ta s dng kh nhiu phng php bo v nhm chc khc nhau. c bit l trong nhng nm gn y, khi m cc phn ng tng hp hu c c thc hin vi cc hp cht c nhiu nhm chc khc nhau th phng php bo v cc nhm chc li cng c pht trin ht sc nhanh chng. Mt trong nhng thnh cng ln nht ca vic s dng phng php ny l s bo v cc nhm chc trong cc phn ng tng hp cc cht Peptt (v d vic tng hp cc protit nh Inxulin, Ribonuclazas). V vy vic nghin cu mt cch c h thng cc phng php bo v cc nhm chc tr nn ht sc quan trng v cn thit cho ngnh ho hc ni chung v ngnh ho hc hu c ni ring.

BO V CC LIN KT C H:

BO V LIN KT C H AXTILEN:

Lin kt C H trong cc hp cht axtilen loi RC ( CH thng cn c bo v trong cc phn ng iu ch cc hp cht c kim loi v nguyn t Hyro y rt linh ng - c tnh axit.

V d:

V vy, khi ta mun thu nhn mt ho cht Grinha n LiC6H4C ( MgBr (V d t n Bromphnylaxtilen) (1) v magi) m nu ta khng tin hnh bo v lin kt C H bng mt tc nhn Grinha v sau cho tc dng vi hp cht c Liti th s thu c hp cht cn thit (hng b).

Trong phng th nghim v trong cng nghip thng hay s dng nhm Triankylsilyl lm nhm bo v cho lin kt C H. V d c th a nhm Trimtylsililclorua vo phn t hp cht Broma (2) sau cho tc dng vi hp cht Grinha v cui cng ti to li lin kt C H bng phn ng thu phn trong mi trng kim.

Ngoi ra, ngi ta cng thng hay chn cc nhm nh cacboxyl, -OH... bo v lin kt C H cc axtilen.

V d:

Hoc l;

BO V LIN KT C H CA HP CHT THM

Phn ng th electrophin l mt trong nhng phn ng rt c bn dng tng hp cc dn xut ca cc hp cht thm khc nhau. Phn ng th xy ra theo hng u tin vo nhng v tr giu in t ca vng thm. V vy, hng phn ng vo nhng v tr cn thit ...(v d v tr c mt in t thp) th cn phi bo v nguyn t hyr ca v tr c mt in t cao.

V d phn ng brm ho cht tecbutylbenzen s cho sn phm ch yu l p bromtecbutylbenzen. V vy thu nhn sn phm th octo th cn phi bo v lin kt C H ca v tr Para nh sau:

a, nh hng oct v Para thng ngi ta s dng cc nhm bo v nh: cacboxyl, Nitr, Sunf.

V d thu nhn hp cht 2,6 diclophenol ngi ta thc hin nh sau:

Cc phn ng cng tin hnh tng t nh vy khi s dng nhm bo v l sunf:

X = CH3 X = CH3 X = Cl

Y = NO2 Y = Br Y = NO2

b, nh hng mta thng ngi ta s dng cc nhm bo v nh: amin, halogen, tite... V d iu ch cc ng phn mtaca cc hp cht ankylbenzen c th tin hnh nh sau:

R = CH3, Iz C3H7 R = C6H3, C2HG5, Iz C3H7, tec C4H9

X = NO2 X = Br

c bit vic s dng nhm bo v l halogen c rt nhiu thun li v sau khi phn ng kt thc, chng ta d dng b kh i bng nhng tc nhn chn lc thch hp.

V d:

BO V LIN KT C H HP CHT BO:

Mc ch chnh ca cc phng php ny l nhm bo v cc lin kt C H ca nguyn t Hyr nm v tr so vi nhm cacbonyl. t c iu ny ngi ta s dng cc phng php bo v trc tip v khng trc tip.

a, Phng php bo v trc tip: CH2 ( > C = CH C6H5V d: Qa trnh bo v nguyn t mtyl ho hp cht decalon -1 cacbon C3 nh sau:

Bo v bng phng php trc tuyn cng c th thc hin qua phn ng chuyn ho thnh hp cht anhyt:

> CH2 ( > CH CHO

b, Phng php bo v khng trc tip

y l phng php bo v cc nhm mtylen hot ng bng cch kh cc nhm cacbonyl bn cnh v sau khi phn ng kt thc th khi phc li nhm cacbonyl bng phn ng oxi ho.

V d: Phn ng mty ho cacbon C2 ca vng A tetrahyromanon nh sau:

BO V NHM AMIN:

BO V CC NHM AMIN BC MT V BC HAI:

Cc amin bc 10 v bc 20 l nhng hp cht rt d tham gia cc phn ng oxy ho v phn ng th. V vy bo v cc nhm ny thng ngi ta thc hin bng cch bo v cc lin kt N H ca cc amin. Di y l mt s phng php bo v c bn:

Phng php Protn ho:

y l phng php bo v cc nhm amin n gin nht. Phn ng xy ra trong mi trng axit v khi nhm nhm amin chuyn ho thnh Protn v ngn cm cc phn ng th khng cn thit

Tuy nhin, phn ng ny khng ngn cn c cc phn ng oxy ho.

Phng php selat ho

y l phng php bo v cc nhm chc amin rt c hiu qu bng s tham gia ca cp electron t do ca nguyn t Nit to thnh mt ni phc (selat) vi cc kim lai chuyn tip. V d c th tin hnh phn ng Benzol ho nhm Hyrxi ca hp cht tirozin sau khi bo v nhm amin bng phc vi ng:

Phc cht c to thnh sau phn ng c th thu phn bng H2S ti to li hp cht amin axit ban u.

4.3.1.3. Phng php axyl ho

y l phng php nhm bo v da vo kh nng d to thnh cc hp cht axyl ca cc nhm amio. Thng thng trong phng php ny hay s dng cc nhm bo v nh focmyl axtyl v benzoyl.

V d:

a, Phn ng s dng phng php bo v focmyl ho iu ch cc amin axit:

b, Phn ng tng hp synfanilamit t anilin:

c, Phn ng dng phng php bo v nhm chc axyl ho (COCF3) tng hp cc hp cht glycozit:

d, Phn ng tng hp ete ca dn xut piperidin bng phng php bo v benzoyl ho nhm amin bc 20:

e, Phn ng bo v bng to ra hp cht diaxyl:

4.3.1.4. Phng php azmtyl ho:

y l phng php da vo phn ng to thnh cc nhm azmtin (cc baz ship) bng phn ng ca cc nhm amin bc 10 vi cc anehyt v xtn.

V d: Phn ng chuyn ho amin bc 10 thnh amin bc 20

4.3.1.5. Phng php: Nitroz v nitr ho:

Phng php nitroz ho c thc hin ch yu vi cc amin bc 20. Sau khi kt thc phn ng nhm amin c phc hi bng phn ng kh c xc tc kim loi hoc trong mi trng axit.

V d:

Phn ng nitr ho to lin kt N N nhm bo v nhm amin, ch c ngha i vi hp cht arginin. O y, ngi ta s dng phng php ny tng hp Poly Li arginin.

4.3.1.6. Phng php to thnh cc lin kt N P v N S

Cc ete ca ( - aminoaxit tc dng vi ibenzylclphtphat c s dng bo v nhm amin trong phn ng tng hp peptit.

Ngi ta cng s dng nhiu hp cht ca lu hunh lm nhm bo v cc hp cht amin:

a. Phn ng ca sunfenylclorua vi cc amin

b. Phn ng ca fenanxylsynfonyclorua vi cc amin:

c. Phn ng bo v bng s to thnh hp cht N surfaxit:

4.3.2. BO V NHM N NH2 CA NHM HYRAZIN:

bo v nhm chc N NH2 ca Hyrazin trong tng hp hu c, ngi ta s dng nhiu loi hp cht khc nhau.

a. S dng nhm tec Butoxicacbonyl lm nhm bo v tng hp 1 Benzoyl 1- Benzythyrazin.

b. S dng phn ng bo v focmyl ho iu chhp cht 1 aminobenzimirazol t 0 Nitrophenyl hyrazin:

d. Bo v nhm N NH2 bng anhyt - tng hp 1 amintetrazol.

4.3.3. BO V NHM O NH2 CA HYRXYLAMIN:

thu nhn cc hp cht O axyl v O ankyl ca Hyrxylamin th cn phi bo v lin kt N H. iu ny c th t c bng nhiu phng php khc nhau. V d c th dng cc hp cht cacsonyl nh sau:

Phng php bo v trn y tuy rng c s dng rt rng ri nhng trong mt s trng hp khi dng phn ng thu phn hp cht thu c sau phn ng ti to li nhm amin th ph hu lung lin kt O- Axyl hoc O- Ankyl. khc phc nhc im ny ngi ta thng s dng nhm Tec Butoxi cacbonyl lm nhm bo v.

III.4. BO V NHM AMIN BC 30 NR3

bo v cc nhm amin bc 30 ngi ta tm cch chuyn ho chung thnh mui amni bc 40 hoc thnh cc hp cht nictin thnh mui ca Pirdin nh sau:

bo v nhm amin bc 30 ca Piniin, trong cc phn ng chuyn ho, ngi ta dng phng php to hp cht N oxit.

V d:

4.4. BO V NHM CHC ANCOL

Ancol tham gia d dng vo cc phn ng ankyl ho, axyl ho, xy ho, hyrt ho... V vy trong rt nhiu cc phn ng tng hp thu c nhng sn phm cn thit th phi bo v nhm ancol c s dng rt rng ri trong cc phn ng tng hp sterit, cc loi ng, glyxerit... Cc phng php c bn thng c s dng bo v nhm chc ancol thng l ete ho, axtal ho v ketal ho.

4.4.1. PHNG PHP ETE HO:

Nhm Hyrxy ca cc hp cht ancol rt d dng tham gia phn ngd to thnh cc hp cht ete khc nhau. Di y l mt s ete thng c s dng bo v nhm chc ancol.

a. Ete metylic:

Cc nhm chc hyrxyl trong hyrcacbon v trong ancol rt d dng mtyl ho bi imtylsunfat trong mi trng kim hoc bi metylioua vi xc tc oxit bc. y chnh l c s ca phn ng dng bo v cc nhm chc ancol bng phng phng php ete mtylic.

b. Ete Tec Butylic:

Nhm tec Butylic thng c s dng bo v cc nhm chc ancol trong cc phn ng tng hp peptit steroit. Ete tec Butylic c th c iu ch vi mt hiu sut kh cao bng phn ng ca ancol v izbutylen vi Metylen clorua c xc tc bng axit:

Sau phn ng c th tch nhm bo v tec Butyl bng phn ng vi trifloaxtic axit khan.

c. Ete alylic:

Trong rt nhiu trng hp c bit l trong mi trng axit yu th c th s dng ete allylic bo v nhm chc ancol.

d. Ete Benzylic:

Nhm bo v benzyl c ng dng rt rng ri bo v cc nhm chc ancol trong cc tng hp ng, nucleozit, glyxrit, aminaxit. Phn ng bo v c thc hin bng s un nng ancol vi benzyl clorua d trong dung mi khng phn cc. V d phn ng chuyn D- glucoza thnh L sorboza c bo v bi Ete benzylic nh sau:

e. Ete triarylmtylic:

Ete triarymtylic c s dng rt rng ri bo v nhm ancol bc 10 trong cc phn ng tng hp ng, nucleozit, glyxerit v steroit. Hp cht bo v c to thnhf khi cho ancol tc dng vi triphenylclomtan.

V d:

Nhm bo v sau phn ng c tc i bng phn ng thu phn trong mi trng axit.

f. Ete trimtysilic:

Nhm trimtyl silyl c ng dng rng ri bo v cc nhm chc ancol trong cacbon hyrat, steroit. u im ln ca phng php ny l nhm bo v rt d dng b y i trong nhng iu kin phn ng khng khc nghit lm. Hp cht bo v thng c thu nhn bng phn ng ca ancol vi trimtylclosilan.

4.4.2. PHNG PHP EXETAL V KETAL HO:

a. Ete tetrahyrfiranylic:

Phn ng ca 2, 3 ihyr 4H- piran tc dng vi ancol trong mi trng axit to thnh ete tetrahyrpiranylic l c s ca phng php bo v axtal:

Phn ng ny c s dng rng ri bo v cc nhm chc ancol trong cc phng php tng hp steroit, nucleotit. Ete tetrahyrpiranylic rt bn vng trong mi trng kim, nhng d dng b thu phn trong mi trng axit cho li hp cht ancol ban u.

b. Cc hp cht axetal.

Cho n nay trong ho hc tc dng hu c ch yu vn s dng Tuy nhin, trong mt s trng hp ngi ta c s dng mt s axetal Ete tetrahyrpiranylic bo v nhm ancol theo phng php axetal. Tuy nhin, trong mt s trng hp ngi ta c s dng mt s axeta khc nh dn xut ca uridin, tetrahyrtifuran, tetrahyrtipiran.

c. Cc hp cht ketal:

Vic s dng nhm bo v tetrahyrpiranyl cho cc nhm chc ancol quang hot dn n mt kh khn l to thnh hn hp ng phn khc nhau. khc phc vn ny trong nhiu trng hp ngi ta thay nhm tetrahyrpiranyl bng mt hp cht axetal i xng (ketal). Nhng ketal thng c s dng bo v nhm chc ancol trong cc phn ng tng hp nh ketal axtn, ketal uridin, ketal ca dn xut tetrahyr 4H piranon 4.

4.4.3. PHNG PHP ESTE HO;

Mt trong nhng phong php c s dng rng ri nht bo v cc nhm chc ancolca cc phn ng xy ra trong mi trng axit hoc l trung tnh l phng php este ho - to thnh cc hp cht axetat, hoc l cc hp cht cacboxylat. Cc phn ng axyl ho ny thng xy ra nhit thng bi phn ng ca ancol vi anhyrit hoc cloranhyrit ca cc axit cacboxylic trong piridin.

a. Cc hp cht axetat:

y l phng php c s dng tng i rng ri bo v nhm chc ancol trong cc hp cht steroit, cacbonhyrat, nuclozit... Hp cht bo v c to thnh bi phn ng ca anhyrit axetic vi ancol cn bo v trong piridin. Sau khi phn ng kt thc th nhm bo v c tch ra bng phn ng thu phn trong mi trng axit.

b. Cc hp cht Benzoat v p notrobenzoat:

bo v cc nhm chc ancol c bit l trong cc hp cht ng thng s dng rng ri phng php benzoat ho. Phn ng to thnh hp cht bo v xy ra gia nhm ancol vi hp cht Benzoyl clorua trong piridin. So vi phng php axetat ho th phng php ny xy ra trong nhng iu kin chn lc tt hn v t c cc phn ng chuyn v hn.

c. Phng php focmiat ho:

Phng php ny c u im ln l d b thu phn phc hi li ancol ban u m khng lm nh hng n cc nhm bo v ca cc loi este khc. Hp cht bo v c to thnh by phn ng ca nhm ancol vi axit focmic v sau khi kt thc phn ng nhm ancol c ti to li bi phn ng thu phn ca bicacbonat Kali trong ru metylic.

V d phng php focmiat ho c s dng bo v nhm ancol trong phn ng chuyn ho cht hyrizoanrosteron thnh testosterron.

4.4.4. PHNG PHP BO V CC IOL:

Cc nhm chc 1, 2 v 1, 3 glycol thng c bo v bng cc axtal v ktal vng hoc cc este vng.

4.4.4.1. Cc axtal v ktal vng

Phng php bo v cc hp cht glycol bng cc axtal v ktal vng c ng dng rng ri trong ho hc steroit, glyxerit, cacbon hyrt. Cc nhm bo v thng c hnh thnh bng phn ng ca hp cht glycol vi cc hp cht cacbonyl tng ng trong mi trng axit. Phn ng c th tin hnh trong cc dung mi nh ixan ete, benzen, tetrametylfocmamit hoc khng c dung mi. Cc nhm bo v loi ny bn trong mi trng trung tnh v mi trng kim, d b thu phn bi axit. Sau y l mt vi phng php hay c s dng.

1. Mtylenaxetal:

Hp cht ny thu nhn c bng phn ng ca glycol vi focmanhyt trong mi trng axit. Nu phn ng tin hnh vi cc ancol a chc th thng to ra mt hn hp nhiu sn phm. V d nu cho focmanhyt tc dng vi D Glucoxit trong HCl th s thu c mt hn hp sn phm iaxetal v triaxetal.

2. Etylien axetal:

Hp cht ny c ng dng ch yu trong tng hp cc loi ng. Nhm bo v c hnh thnh bng phn ng glycol vi axetanhyt, 1, 1 imetxyetanol vi s xc tc ca axit. V d hp cht metyl 4,6 O etylien - ( - D Glucopiranozit c to thnh bng phn ng trao i gia mtyl - ( - D Glucopiranozit vi 1,1 imetxietan vi xc tc H2SO4.

Etylienaxetal l hp cht bn trong mi trng kim nhng d b thu phn trong mi trng axit ti to li hp cht ban u.3. Benzylien axetal:

Hp cht bo v ny c ng dng rng ri trong tng hp ng v glyxrit. Benzylien axetal c to thnh bng phn ng ca cc glycol vi benzanhyt vi xc tc axit. V d phn ng to thnh dn xut benzylien axetal 1,2 v 1,3 ca glyxrin xy ra nh sau:

Benzylien axetal rt bn trong cc iu kin phn ng khc nhau (tr axit). Mt khc mi lin kt bo v ca hp cht cng d b ph v bng phn ng kh c xc tc.

V d:

Ngoi ra bo v cc iol theo phng php ny ngi ta cn s dng nhiu cc hp cht khc nhau nh dn xut ca benzelien axetal, izopropy lien ketal, xyclohecxylien ketal. V dphn ng to thnh hp cht bo v xyclohecxylie axettal gia D Kxiclofuranoza vi xc tc H2SO4 xy ra nh sau:

4.4.4.2. Cc este vng;

bo v cc iol theo phng php ny, thng ngi ta hay phenyborat vng. Phng php ny c ng dng rt rng ri trong cc tng hp ng, nuclofit, glyxerit. Cc hp cht cacbonat c hnh thnh bng phn ng ca glycol vi focgen trong piriin. V d cc nhm glycol ca D glucza c bo v bng hp cht cacbonat vng nh sau:

u im ln nht ca cc hp cht bo v cacbonat l kh bn trong mi trng axit v ch b ph v trong mi trng kim.

Cc hp cht bo v phenolborat vng c to thnh khi cho glycol tc dng vi axit phenylbonic trong cc dung mi nh benzen axtn, ixan y l nhng hp cht bn trong khng kh nhng rt b ph v bi 1,3 propanion. V d phn ng chuyn ho ( - D - Kxylopiranozit thnh dn xut 3 0 axtyl bng phng php phenolborat vng xy ra nh sau:

4.5 BO V NHM CHC CACBOXYL

Trong tng hp rt nhiu khe cn thit phi bo v nhm chc cacboxyl tin hnh phn ng ti cc v tr khc v sau khi phn ng kt thc th tm cachs phn hu nhm bo v khi phc li nhm chc cc boxyl ban u. V d nhm chc cacboxyl c bo v trong phn ng tng hp penyxylin nh sau:

Phng php ch yu l phng php este ho.

4.5.1. PHNG PHP ESTE HO BNG ANCOL:

bo v nhm chc cacbonyl ngi ta tin hnh este ho cc axit caboxyl hoc l cc dn xut ca n bng cc ancol khc nhau. Sau y l mt s phng php c bn:

a.Phng php este ho trc tip cc axit c th thu nhn c cacboxylat cuar mtyl, tyl, benzyl, cc dn xut benzylbng phng phn ng ca axit v ancol tng ng. Cc phn ng ny thng c xc tc bng axit v c hoc mt s axit kim khc nhau.

b.Phng php este ho bng phn ng ca halogenanhyrit axit vi ancol c thc hin trong mi trng kim. Phn ng ny thng dng iu ch tec-butyl cacboxylat.

c.Phn ng este ho ca cc anhyrit axit vi cc ancol c th c xc tc bi axit hoc baz. Mt trong nhng u im ln ca phn ng ny l n to thnh mn este khi cho ancol tc dng vi c anhyrit vng ca cc hp cht iaxit.

V d: Ngi ta ng dng u im tng hp glutamic nh sau:

d.Phng php este ho bng phn ng ca cc dn xut halogen vi cc mui ca axit cacboxylic c s dng iu ch mtyl, tyl, benzyl cacboxylat.

e.Ngoi ra, iu ch este ngi ta cn s dng cc phng php nh trao i este, phn ng ca axit cacboxylic vi olefin, vi iafoankan, v nhng phng php khc.

4.5.2. NG DNG V PHNG PHP TCH CC NHM BO V CA ESTE:

a.Mtyl v tyl este: y l cc nhm bo v c ng dng rng ri trong nhng phn ng anlyl ho v ngng t. Cc nhm bo v ny c th c tch ra bng phn ng thu phn bi axit hoc baz.

b.Tec Butyl este: Hp cht ny rt bn trong cc phn ng thu phn bi baz nhng rt b thu phn bi axit. V vy, n thng c s dng bo v cc nhm caboxyl trong cc phn ng tng hp xy ra trong mi trng kim, c bit l iu ch cc xtn.

V d:

C6H5CH2 CH(COO tec Bu)2 + P O2N C6H4COCl

P O2N C6H4 CO CH2 CH2 C6H5d. Benzyl v cc dn xut benyl este:

Cc nhm bo v ny rt d dng tch i bng phng php thu phn. Nhm benzyl c th b tch i bng phng php thu phn trong mi trng kim hoc l trong mi trng axit vi iu kin khc nghit. Tc thu phn ca cc este ny ph thuc vo nng ca axit, nhit , thi gian, phn ng u im v bn ca cc nhm bo v ny trong mi trng axit yu c p dng tng hp nhiu hp cht m khng th iu ch c trong mi trng kim.

Ngoi ra, bo v nhm chc caboxyl trong tng hp hu c ngi ta cn s dng nhiu nhm bo v khc nhau: 2,4 initr benzensunfophenyl, O nitrbenzhyryl, benzilienyl, phenylaxtylSau phn ng nhng nhm chc ny cng c tch ra bng phn ng thu phn trong mi trng axit hoc baz.

4.6 . BO V CC NHM CHC ANHYT V XTN

Nhm cacbonyl trong cc hp cht anhyt v xtn l nhm chc rt linh ng, tham gia nhiu phn ng khc nhau trong tng hp hu c. V vy, vic bo v n tin hnh mt phn ng theo mun c ngha rt ln. Di y l mt s phng php quan trng thng c s dng.

4.6.1. AXTAL V KTAL HO

4.6.1.1. Cc phng php bo v bng Axtal v Ktal:

a, Phng php 1,3 ixlan Nhm ixlan:

c s dng bo v cc nhm anhyt v xtn trong mi trng kim v trung tnh. Kh nng to thnh hp cht ixlan c sp xp theo dy sau: Cc anhyt > Cc xtn mch h v xycl-hecxannon > xyclopentanon > (, ( - xtn khng no > cc dn xut xut (-mn v ixtn > Cc xtn thm.

Di y l mt vi phng php iu ch cc ixlan t anhyt v xtn:

*Phng php trc tip: Trong phng php ny ixlan c iu ch bng phn ng ca cc hp cht cacbonyl vi tylenglycol trong mi trng axit. Phn ng c tin hnh vi s tham gia ca octeste, l tc nhn tch loi nc. Ngoi xc tc bng axit thng ngi ta s dng cc xc tc nh sunfoaxit, pirinin clohyrat. i vi cc xtn hot ng mnh th c th s dng cc xc tc nh xyt selen, axit malnic

*Phng php trao i: C s ca phng php ny l phn ng trao i gia cc nhm chc cabonyl vi cc hp cht ixolan ca cc xtn c nhit rt thp. Thng hay s dng cc hp cht ixlan ca butanon 2, axtn. Phng php ny c th dng bo v cho cc ixtn c kh nng phn ng tng t nh nhau.

*Mt s phng php khc: iu ch cc ixolan trong tng hp hu c, ngi ta cn s dng mt s hp cht nh etylenxyt vi xc tc clorua thic, sunfit glycol

b, Cc phng php axetal v ketal vng: S to thnh cc hp cht axetal v ketal vng c thc hin bi phn ng ca cc anhyt v xtn vi ancaiol. Cc kt qu nghin cu cho thy rng kh nng to thnh cc ketal bin i theo dy: 2,2 imtyprpaiol 1,3 > etylenglycol > propaiol 1,3.

c. Phng php iankylaxetal v ianxylxtal:

S to thnh cc iankylaxetal v ianxylxtal ch yu ch xy ra vi cc anhyt v cc xtn hot ng mnh. Phn ng xy ra vi xc tc axit gia cc hp cht cacbonxyl vi cc ancol. y l cc hp cht tng i bn trong mi trng trung tnh v mi trng kim.

4.6.1.2. Phng php phn hu axtal v ktal:

Cc axtal v ktal thng c phn hu phc hi li cc nhm chc cacbonyl di tc dng ca axit. Tuy nhin tu thuc vo cc hp cht axtal v ktal, c th n ngi ta s dng axits thch hp. Thng th s to thnh cc axtal v ktal cng d dng bao nhiu th s phn hu bng axit cng nh nhng by nhiu. Mt khc, s phn hu ca cc ketal quang hot thng xy ra trong iu kin khc nghit vi cc tc nhn l nhng axt v c.

4.6.2. POLYTI V I AXTAL V KTAL:

4.6.2.1. 1,3 Ocxatiolan (Polytioketal):

Cc hp cht ny c to thnh khi cho xtn tc dng vi 2-mcaptoetanol trong mi trng axit. Trong mt s trng hp cng c th chuyn ha cc anhyt bng phn ng ny. Ngoi ra cc polytiketal cng c th thu nhn bng phng php ny t cc dn xut ca mcaptoetanol v mcaptpropanol. So vi etylen glycol th cc phn ng ca cc anhyt v xtn xy ra vi mcaptoetanol d dng hn. Mt khc, cng tng t nh ixalan, cc polytiktal rt bn vng trong mi trng trung tnh v baz nhng khng bn trong mi trng axit. Cc polytiktal thng b phn hu bi cc axit v c trong ancol hoc ixan. Nhc im c bn nht ca phng php ny l vic to thnh hp cht polytiktal dn n s xut hin trung tm bt i v do c th to thnh sn phm l nhng ng phn quang hc khng i quang.

4.6.2.2. itiaketal v itiktal:

Cc hp cht ny c th thu nhn bng phn ng ca cc hp cht cacbonyl. Vi ankylmcaptan hoc imcaptan trong mi trng axit. Thng hay s dng cc tc nhn phn ng nh: 1,2 imcaptotan, tylmcaptan. Cc itiaketal v itiktal u bn trong mi trng trung tnh v baz nhng khng bn trong mi trng axit. phn hu cc hp cht ny tt nht l s dng khng phi axit m cc mui ca thu ngn (II) trong cc dung mi khc nhau.

4.6.3. CC DN XUT ENOL V NAMIN

y l phng php bo v c s dng rng ri trong ho hc sterit, c bit l i vi cc - xtn cha no. V vy cc hp cht c ngha ch yu l cc ienol v ienamin.

4.6.3.1. Cc ete enol v tienol:

Phn ng chuyn ho cc - xtn cha no thnh cc ete ienol thng xy ra di tc dng ca este octfocmiat hoc 2,2 imtxypropan trong ancol vi xc tc axit. thu nhn ete ienol thng s dng cc iol hot ng mnh, v d nh benzylmcaptan.

Cc ete enol v ienol cng nh cc dn xut ca chng rt bn trong mi trng kim nhng rt d b phn hu bi cc axit. Ngoi ra, phc hi li cc nhm chc cacbony cng c th phn hu cc ienol bng mui thu phn (II).

4.6.3.2. Enanin v cc mui ca enamin:

Cc hp cht enamin thng c dng bo v cc nhm anehyt v - xtn cha no trong cc hp cht sterit. ti to li cc nhm cacbonyl ban u, c th thu phn cc enamin bng cc dung dch axit hoc bng kim long.

4.6.4. SEMICACBAZON, OXIM V CC DN XUT HYRAZON;

4.6.4.1. Semicacbazon:

Trong nhng trng hp, c bit l trong ho hc sterit cc hp cht semicacbazon c iu ch rt d dng. Hp cht semicacbazon rt bn di tc dng ca NaBH4, LiBH4 v trong mi trng kim. Trong ho hc hyrat cacbon, hp cht semicacbazon c s dng bo v nhm anhyt ca cc hp cht mch h khi tin hnh phn ng ankyl ho cc nhm ancol. phn hu cc semicacbazon ti to li cc nhm cacbonyl thng tin hnh phn ng thu phn trong axit mnh.

4.6.4.2. Oxim

Hp cht bo v lai ny c bn vng tng ng vi semicacbszon nhng phn ng phn hu n xy ra kh khn hn. Phn ng thu phn hp cht xim ti to li nhm cacbonyl ban u cng c tin hnh trong mi trng axit nhng phi c thm mt s cht xc tc khc. Trong mt s trng hp c th s dng phng php xi ho trong mi trng axit.

4.6.4.3. Dn xut hyrazon:

Hp cht 2,4 initrphenyl hyrazon c s dng ch yu nh tnh anhyt v xtn cn bo v nhm chc th t hn v phn ng phn hu n xy ra rt kho khn. Tuy vy, trong cc phn ng tng hp v chyn ho cc hp cht steroit hp cht ny nhiu khi cng c s dng. Nhm bo v thng c tch ra bng phng php kh vi cc tc nhn nh clorua thic (II), clorua thic (III), Liti nhm hyrua..

Hp cht N, N imtylhyrazon l mt trong nhng hp cht kh l tng dng bo v cc nhm anhyt v xtn v rng vic ti to li cc hp cht cacbonyl sau phn ng c thc hin trong nhng iu kin rt nh nhng trong mi trng trung tnh.

CHNG 5

S XI HO - KH

S xi ho v s kh l hai hin tng c lin quan mt thit vi nhau v khng th tch ri nhau c, khng c s xi ho no m li khng c s kh ng thi vi n. Hai qu trnh c coi l mt: S xy ho - kh. Trong thc t ta ni mt phn ng no l xy hohy l kh ch l quy c nhn mnh tng mt. S xy kho - kh l mt khi nim tng i phc tp. V vy, trc khi xt n c ch phn ng ny ta cn cp n vn ny.

5.1. S XI HO - KH V C CH PHN NG.

5.1.1. Quan nim v s xy ho - kh trong ho hu c:

Trc kia ngi ta cho rng s xy ho l qu trnh cng thm xy, cn s kh l qu trnh tch bt xy, hoc tng hm lng tng i ca hyr trong phn t. nh ngha khng c tnh tng qut, tuy rng do s thun tin v thi quen ngi ta vn dng n trong vic phn chia cc phn ng ca hp cht hu c.

Trong ho v c, phn ng xy ho- kh thng c trng bng s thay i ho tr hoc s chuyn dch mt s electron. Trong ho hu c quan nim khng c dng v nguyn t cacbon trong phn t hu c lun lun c ho tr 4, cn nhng phn ng c s chuyn dch hn cc electron th t gp.

V nhng l trn, hin nay ngi ta thng nh ngha s xy ho - kh da trn c s bin i ca nhng i lng c tnh cht quy c gi l s xy ho hoc bc xy ho.

S xy ho l s in tch quy c ca nguyn t, tnh c khi gi thit rng phn t gm ton nhng in n gin tri du kt hp li. Ni mt cch khc, s xy ho l s in tch xut hin nguyn t trong phn t nu nh xy ra s dch chuyn hon ton tt c cc cp electron lin kt v pha nguyn t no c m in tng i ln hn. (Nu hai nguyn t ng nht lin kt vi nhau th khng c s chuyn ch , v nh vy khng lm xut hin in tich).

S xy ho c k hiu bng ch n (t ting Anh oxidation number) v biu th bng s Ar rp cng vi du in tch v ghi pha trn k hiu ca nguyn t. Th d:

S xy ho l mt khi nim c tnh hnh thc, v tt c cc lin kt cng ho tr gia hai nguyn t thuc hai nguyn t khc nhau u c coi nh l nhng lin kt ion in hnh, m thc ra khng phi nh vy: phn ln cc lin kt ch phn cc t nhiu m thi.

Mt nguyn t c th c nhiu s xy ho khc nhau, tu theo bn cht v s lng cc nguyn t lin kt vi nguyn t ca nguyn t trong phn t. Th d: cacbon c s xy ho (k hiu nC) t -4 n +4 trong dy cc hp cht sau:

Hp cht: CH4 CH3OH C CO CO2nC : -4 -2 0 +2 +4

Ta c th tnh s oxy ho cho mt nguyn t nht nh trong phn t bng cch ly tng cng cc in tch xut hin nguyn t khi cho ion ho tt c cc lin kt. Th d:

Cng c th xc nh s xy ho trung bnh cho cc nguyn t ca mt nguyn t nht nh trong phn t. Khi y ta phi tun theo mt s quy tc sau:

a. Tng i s cc xy ho trong phn t lun lun bng o, trong ion bng s in tch ca ion.

b. S xy ho ca mt nguyn t dng n cht u bng 0.

c. Trong cc hp cht, hydr c s oxi ho +1 ( tr trng hp cc hydrua kim loi, trong nH = -1), xy c s oxi ho -2 ( tr trng hp cc peoxyt v mt s hp cht khc), kim loi c s oxy ho dng v bng ho tr ca n.

Th d tnh s oxy ho trung bnh:

CH4 nC + 4nH=0

NC + 4(+1)=0

nC= -4

CH3OH nO + 4nH + nO=0

nC + 4(+1) + (-2)=0

nC= -2

CH3CH2OH 2nC + 6nH + nO=0

nC + 6(+1) + (-2)=0

nC= -2

CH3COOH 2nC + 4nH + 2nO=0

2nC + 4(+1) + 2(-2)=0

nC= -2

Ta nhn thy rng s oxy ho trung bnh ca cacbon chng hn s trng vi s oxy ho tnh cho tng nguyn t cacbon khi trong phn t ch cha mt nguyn t cacbon ( th d CH4, CH3OH,.) hoc cha 2 nguyn t C ging ht nhau:

Th d: CH3 CH3, CHO CHO, ..

Trong cc thnh phn khc, s oxy ho tnh cho tng nguyn t bao gi cng l mt s nguyn hoc 0, th s oxy ho trung bnh c th l mt s thp phn, th d s xy ho trung bnh ca cacbon trong phn t prpan bng 2,67, trong phn t butan bng -2,5.

Bn cnh khi nim s oxy ho, trong ho hu c cn mt khi nim tng ng gi l bc xy ho. Theo nh ngha, bc xy ho ca nguyn t cacbon l s nhm hydrxy c th xut hin nguyn t cacbon, nu gi thuyt l phn t b thu phn hon ton.

Theo quan nim ny th cacbon trong phn t hu c c th c 5 bc oxy ho khc nhau: 0, 1, 2, 3, v 4. (Xem bng trang sau).

Khi nim oxy ho ( v khi nim bc oxy ho cng vy) cho php hnh dung mc tng i kh nng oxy ho hay kh ca mt cht. S oxy ho cng ln th kh nng oxy ho ( hay l b kh ) cng tng, v kh nng kh ( hay b oxi ho) cng gim. T y ta c th nh ngha: Qu trnh oxy ho l qu trnh lm tng s oxy ho cht phn ng vag lm gim s oxy ho tc nhn phn ng, cn qu trnh kh l qu trnh ngc li. Ni chung, oxy ho - kh l qu trnh bin i s oxy ho (hay bc oxy ho)

nh ngha trn v s oxy ho - kh c tnh cch tng qut v bao hm c tt c cc nh ngha c. Trong ho hu c, ngoi nhng phn ng oxy ho - kh bng cc tc nhn oxy ho hay cc tc nhn kh.

Bng phn loi cc nhm nguyn t theo bc oxy ho ca cacbon.

S xy ho ca cacbon trong mt s phn t hu c v qu trnh xy ho - kh

Thng thng nh xy, hyro, pemanganat kali, axit crmit cn nhiu phn ng khc cng c coi l phn ng xy ha - kh. Th d cc phn ng halgen ho ho v nitro ho hyrocacbon, phn ng dhalgen ho dn xut ihalgen, phn ng cacbxyl ho axit cacbxylic.v.v. Trong khi nhng phn ng nh thu phn dn xut halogen v hp cht c kim, este ho v thu phn este khng thuc loi phn ng xy ho kh.

Khi cn bng phng trnh phn ng xy ho kh trong ho hu c ngi ta cng p dng nguyn tc thng bng s xy ho nh trong ho v c. Th d c s phn ng:

Trong tanol l cht kh v s xy ho ca cacbon tng 4 n v (t -1 tanol n +3 axit axtic) cn pemanganat kali l cht xy ho, v s xy ho ca mangan gim 5 n v (t +7 KmnO4 n +2 MnSO4). m bo nguyn tc thng bng s xy ho ta phi ly 5 phn t tanol v 4 phn t pemanganat kali, cn s phn t H2SO4 c ly sao cho tng ng vi s ion Mn2+ v K2+ sinh ra trong phn ng. Do ta c th vit:

5CH3CH2OH + 4KmnO4 + 6H2SO4 5CH3COOH + 4MnSO4 + 2K2SO4 + 11H2O

Nh vy quan nim v xy ho kh da theo s bin i s xy ho c th trong c ho v c ln ho hu c.

5.1.2. C ch phn ng xy ho - kh

nh ngha trnh by trn v xy ho - kh khng ni ln iu g v c ch cc phn ng c. Ta bit rng phn ng xy ho - kh c th xy ra theo kiu ng ly hay d ly. Tuy vy c ch xy ho - kh l mt vn rt phc tp, v c ch rt a dng v thng bin i nhiu tu theo bn cht ca tc nhn xy ho - kh c dng. Nhiu ngi c gng h thng ho cc c ch xy ho - kh vo mt s loi nht nh. C ch ca cc phn ng xy ho - kh c tp trung ni n 5.2 v 5.3. Di y l mt s loi c ch xy ho - kh ph bin.

5.1.2.1. Chuyn dch trc tip electron:

S tng qut:

A + e B

hoc B e A

Th d:

Kh hp cht cacbnyl bng halri kim loi:

Chuyn ho gi ion v gc t do:

5.1.2.2. Chuyn dch nguyn t hyr:

S tng qut:

Th d:

hoc:

5.1.2.3. Chuyn dch ion hyrua

S tng qut:

Th d:

hoc:

5.1.2.4. Chuyn dch cp electron

S tng qut:

Th d:

hoc:

5.1.2.5. To este trung gian:

Cht phn ng v tc nhn tc dng vi nhau to thnh este trung gian (thng l este v c), sau este b phn tch:

Z thng l CrO3H, MnO3, SeO2HTh d:

5.2. Cc phn ng xy ho:

5.2.1. xy ho lin kt ca Hyrcacbon

Ta bit rng nng lng phn ly cc lin kt trong phn t alkanthngf khng khc nhau nhiu, cho nn t c phng php xy ho lm dt mt cch chn la hoc lin kt C C hoc lin kt C H m khng ng n phn t ni chung. Tuy vy, nng lng phn ly ca cc lin kt C H bc ba hay cc v tr alyl v benzyl yu hn cc lin kt khc mt cch r rt, do ta c th ch xy ho cc lin kt m phn cn li ca phn t vn c nguyn vn. Th d:

Phn ng xy ho cc arylalkan bng Cr(VI) c nghin cu tng i nhiu. Tluen b xy ho thnh axit benzic, iphnylmtan to ra benzphnon cn triphnylmtan to ra triphnylcacbinol. Tc xy ho ph thuc nhiu cu to ca hyrcacbon. Trong trng hp xy ho, nhm p mtyl lm tng tc , cn nhm p nitr lm gim tc , hiu ng n c t hp tuyn tnh vi +, = -1,4. Nu hai nguyn t hyr tham gia phn ng c thay bng teri, tc phn ng s gim 6,4 ln, iu chng t rng tc phn ng xy ra s phn cch lin kt C H. Tuy vy c ch ca giai on ny ni ring cng nh ton b phn ng ni chung cn cha r rng.

Phn ng xy ho nhm alkyl nhn thm bng pemaganat kali cng thng to ra axit. Cc dn xut th nhn ca toluen b xy ho to thnh axit benzic tng ng. So vi CrIV th MnVII thng xy ho mnh hn.

Chng hn 2-5 ibrm-p-xylen b xy ho c hai nhm mtyl bi penmanganat Kali, nhng ch xy ho mt nhm myl bi axit crmic.

Bt k cht xy ho l CrVI hay MnVII, phn ng xy ho nhm alkyl vi vng benzen thng xy ra v tr (to ra cc axit benzic tng ng). Tuy vy, cn lu rng nhm alkyl bc 3 th d t- butyl rt kh b xy ho v khng cn nguyn t hyr. 5.2.2.1. XY HO LIN KT CA HYRCACBON

5.2.2.2. zn phn

Hp cht c ni i C = C tc dng vi zn sinh ra znit. C th phn lp c znit, nhng ngi ta thng em phn hu n bng cch kh thnh hai phn t hp cht cacbnyl. Cng c th kh znit thnh hai phn t alcol (tc dng ca LiAlH4) hoc xy ho thnh xton v cacbxylic (tc dng ca H2O2).

C ch ca giai on to thnh znit c th nh sau:

Nu qu thc c to ra sn phm trung gian III v Iv nh nu s trn th III c th ime ho

hoc chuyn ho thnh hyrpexyt.

Trong mt s trng hp, th d zn ho (CH3)2C=C(CH3)2, ngi ta tch c sn phm V, v nu c zn ho trong mtanol c th phn lp c hyrpexyt:

Mt dn chng na v c ch zn ho trn l s to thnh cc sn phm cho: theo c ch nu xut pht t mt alken khng i xng RCH = CHR ta phi c 3 znit khc nhau:

Trong thc t, khi zn ho nhng hp cht nh penten-2, hexen-2, lat mtylngi ta phn lp c c ba loi znit trn cc dng ng phn cis-trans tng ng.

Cc hp cht c ni ba C C v hp cht thm b zn ho kh hn alken.

5.2.2.2. ihyrxy ho:

Mun cng hai nhm OH vo ni i (ihyrxy ho) c th dng OsO4 hoc KmnO4 trong mi trng kim. l nhng phn ng cng theo kiu cis.

Khi dng cht xy ho l OsO4 c ch phn ng nh sau:

Ngi ta phn lp c este vng trung gian I.

Khi dng KmnO4 trong mi trng kim, ta c c ch:

Hin nay, tuy cha phn lp c este vng MnV nhng c chng c khc v c ch

trn, c th l khi dng Mn18O(-)4 ngi ta thu c: . Ngoi ra,

chng minh rng phn ng chy theo kiu cis, ngi ta ihyrxy ho axit d,l-tactric, ng nh d on theo c ch trn.

Mun trans-ihyrxy ho ni i C=C ngi ta dng H2O2 v axit fomic. Trong trng hp ny, axit pefomic sinh ra t H2O2 v axit fomic pxy ho ni i theo kiu cng cis, sau pxit sinh ra s b thu phn theo c ch SN2 vi s quay cu hnh, kt qu xt ton b th phn ng chy theo kiu trans:

Epxy ho:

Thu phn:

Do c tnh cng trans ca phn ng, khi cho H2O2 v HCOOH tc dng vi xyclohexen ta c trans-1,2-xyclohexandiol

5.2.2.3. Oxy ho ct mch:

Ni i C=C c th b oxy ho ct mch theo cc s trn nh tc dng ca nhiu cht oxy ho khc nhau, ph bin l cc cht oxy ho pemanganat v bicromat trng mi trng axit.

C ch phn ng cn cha c r rng. Cng c th trong phn ng sinh ra nhng sn phm trung gian l glycol hoc este ca n.

Ni ba CC thng kh b oxy ho hn ni i. Axtylen b oxy ho bng pemanganat kali to thnh mt hn hp sn phm trong c axit xalic.

Vng thm cng c th b oxy ho t mch bi cc cht oxy ho mnh. Khi oxy ho benzen v naphtalen bng V2O5 ta c ln lt anhydrit malic v anhydrit phtalic.

5.2.3. XY HO ALCOL:

5.2.3.3. xy ho mnalcol thnh hp cht cacbnyl

S oxy ho cc alcol bc mt v bc hai bng pemngnat kali xy ra rt chm trong dung dch trung tnh, nhng thng li rt nhanh trong dung dch baz v axit mnh.

Kho st phn ng xy ho benzhydrol (C6H5)2CHOH trong dung dch trung tnh v baz, ngi ta thy: V = k [alcol][MnO4-][OH-] hiu ng ng v 250C khi oxy ho (C6H5)2CDOH c gi tr bng 6,6; benzphnn sinh ra khng cha oxy t pemngnat kali. T cc d kin ngi ta ngh c ch phn ng nh sau:

Kho st phn ng oxy ho alcol izppylic bng axit cromic ngi ta thy tc phn ng trong dung dch axit axetic ln hn trong dung dch axit v c vi cng gi tr v H0; khi thay th nguyn t -hydro bng teri 250C tc gim 6,6 ln, trong khi thay th cc nguyn t - hydro bng teri hu nh khng lm thay i tc phn ng:

T cc d kin ngi ta ngh c ch phn ng nh sau:

Sau :

Hoc:

5.2.3.2. xy ho ct mch 1,2 iol

Cc 1,2 iol c c tnh khc v mnalcol ch chng b xy ho bi axit peiic v ttraxtat ch lm t lin kt

Khi xy ho bng HIO4 phn ng i qua mt este vng trung gian:

Nhng th nghim dng 18O cho thy rng nguyn t xy cacbnyl sn phm cng chnh l nguyn t xy glycol.C ch to este vng trung gian ca phn ng trn c xc nhn bng cc d kin ng hc v quang ph, dn chng c bit l cc glycol vi hai nhm trans-OH th d trans-9,10-calindiol khng phn ng vi axit peiic.

Khi xy ho 1,2 -ddioolbng Pb (CH3COO)4 ngi ta cng c nhiu d kin cho thy phn ng xy ra theo c ch vng. Th d phn ng c bc mt ni i vi mi cht phn ng gim i, cis-ddiolb xy ho nhanh hn trans-iol tng ngC ch vng nh sau:

Tuy nhin, c mt s trans-1,2-ddiol li d phn ng hn dng cis tng ng. V d trng hp 9,10 ihyrphnantren-9,10 -ddiol dng trans phn ng nhanh hn dng cis 9,4 ln, trans 9,10 ecaliniol khng phn ng vi HIO4 nhng li b xy ho bi Pb(CH3COO)4. Nh vy, c th y phn ng xy ra theo c ch khng vng.

1,2-iol cng c th b xy ho ct mch bi axit crmic v phn ng cng chy theo c ch este vng trung gian.

5.2.4. XY HO ALEHYT V XTN

5.2.4.1. xy ho bng tc nhn v c:

Cc hp cht cacbnyl, nht l alhyl c th b xy ho bi cc hp cht xy ho khc nhau nh MnVII, CrVI, Cu'', AgI, CeIV

Nghin cu phn ng xy ho alhyt thm bng KmnO4 trong dung dch trung tnh ngi ta thy rng phn ng c bc mt i vi alhyt cng nh i vi pemanganat, hiu ng ng v teri bng 7, nu dng KMn18O4, 18O s xut hin trong thnh phn phn t ca axit thm sinh ra, cc nhm th vng thm ch c nh hng yu n tc phn ng ( = -0,25).

Ta c th m t c ch phn ng xy ho bng s sau:

Phn ng xy ho alhyt bng axit crmic c nhiu nt tng t phn ng xy ho alcol cng bng tc nhn . C ch phn ng nh sau:

Trong trng hp dng C6H5CDO ngi ta thy hiu ng ng v bng 4,3, iu chng t giai on phn ct lin kt cacbon-hyr quyt nh tc chung ca phn ng.

Gia hai phn ng xy ho alhyt v xy ho alcol bng axit crmic c hai im khc nhau ng k. Mt l, cc nhm th ht electron xc tin s xy ho alhyt ( = +1,02) nhng li lm gim nh tc xy ho alcol ( = -1,0). Hai l thay th dung mi nc bng axit axetic khng lm tng mnh tc xy ho alhyt nh thy khi xy ho alcol.

Khc vi anhyt, xtn tng i kh b xy ho bi pemangant kali v axit crmic. Tuy vy cc xtn vng d dng b xy ho thnh axit icacbxylic. Th d:

C th cc xtn tc dng di dng enol to ra este v c trung gian, sau este ny b thu phn:

ng ch l nhm -metylen ca xtn cng nh aldhyt c th b xy ho thnh cacbnyl th hai nh tc dng ca xyt selen:

Trong phn ng trn, tc nhn xy ho trc tip c l l axit selen: axit ny tc dng vi lin kt ca dng enol theo s :

5.2.4.2. xy ho bng tc nhn hu c:

Nhng phn ng xy ho alhyt bng cht hu c cn c th c coi l phn ng kh i vi cht hu c . Nhng phn ng ny thng chy theo c ch chuyn dch in hyrua, m tiu biu hn c l phn ng Cannizar v phn ng Tissenc.

a. Khi c tc dng ca mt baz mnh nh NaOH chng hn cc alhyt thm v alhyt bo khng c nguyn t -hyr s tham gia phn ng Cannizar, trong mt phn t alhyt b xy ho thnh cacbxylic tng ng, cn phn t alhyt b xy ho thnh alcol tng ng. Trong phn ng ny, thot tin aion HO(-) tc dng vo nguyn t cacbon-cacbnyl ca mt phn t alhyt:

Sau aion sinh ra s chuyn in hyrua sang nhm cacbnyl ca phn t alhyt th hai:

hoc

Phn ng trn c bc mt i vi b v bc hai i vi anhyt, phn ng ca RCHO trong D2O - kim to ra alcol khng cha eteri, iu c s chuyn dch trc tip hyr t phn t anhyt th nht sang phn t anhyt th hai.

Phn ng Cannizar c th xy ra gia hai nhm C = O ca mt phn t (Th d: C6H5CO CHO) hoc gia hai nhm C = O ca hai phn t khc hn nhau(th d: (CH3O)2C6H3CHO v HCHO2.

b. Tt c cc alhyt khng c hoc c -hyr ni chung u tc dng c vi alkxyt nhm, khi y mt phn t alhyt b xy ho to ra axit cacbxylic, cn phn t khc b kh to ra alcol, hai sn phm ny dng este (Phn ng Tisenco):

Khi dng hn hp hai alhyt khc nhau ta c th thu c ti bn este RCOOCH2R', R'COOCH2R, RCOOCH2R v R'COOCH2R'. Tng t phn ng Cannizar, phn ng Tisenc chy theo c ch chuyn dch in hyrua:

5.3. CC PHN NG KH

5.3.1. KH LIN KT B CACBON CACBON

5.3.1.1. Kh bng hyr trn b mt cht xc tc kim loi

Bt k c nhm th l y electron cc lin kt bi cacbon-cacbon u c th b hyr ho trn b mt cht xc tc kim loi. Nhng cht xc tc hay dng l Ni, Pt, Rd, Ru v CuCr2O4. Kh ho v hyr ho l nhng qu trnh thun nghch i vi nhau. Qa trnh hyr ho pht nhit (28-33kcal/mowl), cn qu trnh hyr ho thu nhit. C ch ca phn ng hyr ho trn b mt cht xc tc kim loi l mt vn phc tp cn cha c gii quyt trn vn.

Phn ng hyr ho lun lun xy ra theo kiu cis. Vy cc alkyn b hyr ho to thnh cis-alken.

Cc axit imtylmalic v imtylfumaric khi b xy ho to ra nhng ng phn khc nhau ca axit imtylsucxinic:

V kh nng phn ng, alkyn d b hyr ho hn alken. Nu so snh kh nng phn ng hyr ho ca cc lin kt bi cacbon-cacbon vi cc lin kt b khc ta c th t gn ng nh sau:

> dn xut ca naphtalen > RC = O > O dn xut ca benzen

Vng benzen khi b hyr ho thng khng dng li giai on cng mt phn t hyr, v anken d b hyr ho hn vng benzen rt nhiu. Th d mt mol benzen tc dng vi mt mol hyr khng cho xycllexaien hay xyclhexen m cho 1/3 mol xyclhexan. Trong iu kin nh vy naphtalen b kh cho ta ttrahyrnaphtalen (ttralin). Tuy vy, i vi nhng hp cht thm nhiu vng ngng t hn nh antraxen, phnantren ta li d dng cho phn ng dng giai on cng hyr vo hai nguyn t 9, 10 v nhng v tr ny hot ng hn c:

5.3.1.2. Kh bng cc tc nhn khc:

Cc alken -1 d dng b kh bi hyrua nhm to thnh alken:

iboran cng kh c alken tng t nh vy

Tc cng iboran vo anken s gim khi s nhm alkyl ni i tng ln.

Khi dng iboran kh alkyl ta c cis.alken.

Tri li nu dng cht kh l natri trong amniac lng ta s c trans-Anken:

Dng natri-amniac kh vng thm ta c sn phm cng 1,4 l xyclhexaien khng lin hp:

Cc nhm th y electron (th d OCH3) trong vng benzen nh hng phn ng to ra dn xut 2,5 ihir, trong khi cc nhm th ht electron (th d COOH) li nh hng to ra dn xut 1,4-ihyr:

Naphtalen b hyr ho bi natri-tanol trc tin cho ta 1,4-ihyrnaphtalen nhng cht ny khng bn, n chuyn ho ngay thnh 1,2- ihyrnaphtalen (c hai phn ng u to nhit)

5.3.2 KH ALEHYT V XTN:5.3.2.1. Kh thnh alcol:

Alhyt v xtn ni chung d b kh thnh alcol bc mt v bc hai. Cc cht kh c th l: natri trong ru, hyr trn niken Rany, hyrua litinhm, hyrua natribo

a. Kh bng LiAlH4 v NaBH4:

V thc cht cc phn ng ny l phn ng cng nucleophin vo nhm cacbnyl:

Cc hyrua kim loi nh LiAlH4 thng khng kh lin kt bi cacbon cacbon v th chng c th kh chn lc nhm C = O ca hp cht cacbnyl cha no.Th d:

Tuy vy iu kin nhit phng phn ng kh trn to ra alcol no C6H5CH2CH2CH2OH.

Dng NaBH4 lm cht kh c u im l tnh chn la cao v c th thc hin phn ng trong mi trng nc. NaBH4 khng kh cc nhm C = C, COOH, COOR9v tnh kh chn la, xem bng XV-3)

b. Kh bng izproopylat nhm:

Mt s alcolat kim loi, c bit l izprpylat nhm c kh nng kh alhyt v xtn thnh alcol tng ng theo mt qu trnh thun nghch.

Qa trnh thun, dng kh hp cht cacbny, c gi l phn ng Mecvai-Pondoo-Vecly, cn qu trnh nghch, dng xy ho alcol, c gi l phn ng Openao.Bn cht ca cc phn ng trn l qu trnh chuyn dch ion hyrua t alcolat nhm sang nhm cacbnyl qua mt trng thi chuyn tip vng:

Dn chng v s chuyn dch ion hyrua l khi dng izprpylat nhm c cha - teri RRCDOH.Khi kh bng izprpylat nhm ngi ta chng ct cho axtn thot ra khi mi trng phn ng v cn bng v bn phi. Tri li khi mun xy ho alcol ngi ta dng d axtn v dng t-butylat nhm lm xc tc, v cht ny khng cn - hyr c th kh axtn m ch c th chuyn alcol cn oxy ho thnh alcolat tng ng.

5.3.2.2. Kh thnh hyrcacbon no:

C mt s phng php kh nhm C = O thnh nhm CH2, quan trng nht l phng php Kizne Vnf v phng php clemmenxen.Trong phng php clemmenxen ngi ta un nng alhyt hoc xtn hn hp km trong axit clohyric m c. C ch ca phn ng cn cha r rng, ch bit rng sn phm trung gian khng phi l mt alcol v cht ny khng b kh thnh hyrcacbon trong iu kin ni trn.

Nu trong phn t anhyt v xtn c nhng nhm th khng bn trong mi trng axit, th tt nht nn dng phng php Kizne Vnf. Theo phng php ny hp cht cacbonyl c chuyn thnh hyraz tng ng, ri un hyrazon vi kim c hoc tylat natri:

C ch ca giai on chuyn ho hyrazon thnh hyrcacbon c th c m t bng s sau:

Phng php Kizne Vnf c Hong Minh Long ci tin bng cch un trc tip hp cht cacbnyl vi hyrazin v kim trong tylenglycol di p sut thng (v th c tn gi phng php Hong Minh Long). Cram li ci tin thm bng cch dng i-butoxyt kali lm baz v imtylsunfxyt lm tng dung mi, do c th thc hin phn ng ngay nhit phng m hiu sut t c vn cao.

5.3.3. KH AXIT CACBOXYLIC V CC DN XUT CA CHNG:

Axit cacbxylic RCOOH khng b kh bng cc ch kh thng thng, nhng li d b kh bi LiAlH4, v mt vi cht khc to thnh alcol bc nht:

C ch ca phn ng c th nh sau:

Este d b kh hn axit cacbonxylic, phn ng kh este bng LiAlH4, xy ra tng t phn ng kh alhyt v xtn.

Ngoi LiAlH4, este cn c th b kh bi mt s cht khc nh hyr trn cromit ng, natri trong tanol

Phng php kh este thnh alcol bng natri trong tanol c gi l phng php Buv-Blng. Trc khi tm ra LiAlH4, phng php Buv-Blng c dng rt ph bin.

Clorua v anhyrit axit cng d b kh bi LiAlH4, thnh alcol bc nht:

Clorua axit c th b kh bi hyr trn cht xc tc Pd to thnh alcol, qua cht trung gian l alhyt:

ngn cn giai on chuyn alhyt thnh alcol ngi ta dng BaSO4 lm cht c i vi Pd (phng php kh Rzenmun):

Mun kh clorua axit thnh alhyt ta cn c th dng cc cht kh l liti hyrua hoc tri-t-butxy nhm hyrua. Trong trng hp dng cht kh l hn hp natri trong te ta s c este ca eniol:

Kh nng phn ng ca mt s nhm chc i vi cc cht kh khc nhau:

Phn ngHyr ho c xc tcLiAlH4 trong teB2H6 trong THFNaBH4 trong etanolNaBH4 + AlCl3 trong iglime

RCH = CHR RCH2CH2RTCHO RCH2OH

RCOR RCHOHR

RCHO

RCOCl RCH2OHRCOOR( RCH2OH + ROH

RCOOH ( RCH2OH

RCOO(-) ( RCH2OH++

+

+

+

-

--+

+

+

+

+

+++

+

-

+

--+

+

+

-

-

-++

+

+

+

+

+

THF: ttrahyrfuran, iglime: (CH3OCH2CH2)2O

5.3.4. KH CC HP CHT CHA NIT:

S kh cc hp cht cha nhm C N, - C = N v CONH2 ni chung tng t s kh hp cht cacbnyl, sn phm sinh ra thng l amin. Th d cc xim b kh bng LiAlH4 thnh amin bc nht:

Phn ng kh xim chy chm hn phn ng kh xtn. Amit b kh bi LiAlH4(NaBH4 khng c tc dng) tng t este. C ch phn ng kh nh sau:

Amit, xim cng nh nitrin u c th b kh bng hyr nh cht xc tc kim loi.

Cc hp cht nitr v nhng dn xut th ca chng rt d b kh bng nhiu tc nhn khc nhau. S kh trong mi trng axit hoc kh bng hyr trn cht xc tc kim loi thng cho ta hp cht amin:

S kh nhm nitr trong mi trng kim phc tp hn nhiu v c nhng phn ng ngng t gia cc sn phm kh khc nhau:

Tuy s kh hp cht nitr phc tp nh vy, nhng nu chn cc cht kh thch hp ngi ta c th cho phn ng u tin dng li mt giai on nht nh no .

CHNG 6

S CHUYN V

Trong nhng chng trc, chng ta thng kho st cc phn ng ca hp cht hu c trn c s ca nguyn tc bin i cc tiu cu to, ngha l tha nhn rng trong phn ng trong phn ng ho hc ch cc nhm chc thay i, cn phn gc hyrcacbon vn c bo ton. Nguyn tc t ra ng n trong rt nhiu trng hp, v rt b ch trong vic xc nh cu t