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5/25/2018 Quy Lu t Th Vng Benzen

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QUY LUT TH ELECTROPHINVO VNG BENZEN

Ngibin son:Hoavang06


2/17

BENZEN (C6H6)

Vng benzen l mtvng hpbi6 nhm C-H, minguyn tCcn limtha tr;

Cc nguyn tC sdngha trny tothnh 3 niigingnhxiclohexadien.

3 niiny khng cnhm c schuynch thng xuyngiacc ninv niitothnh vng khp kn.

t ng ng v i

Cng thcKekule(1865):


3/17

BENZEN (C6H6)

Quan nimhinivcutrc cabenzen:Benzen c cutovng ngphng,6 nguyn tC v 6 nguyn tH

nmtrn mtphngl lcgic u.Su nguyn tC trong benzen utrngthi lai ha sp2tothnh

mtphngs. Minguyn tC cn mtelectron p chalai ha xen phhai pha vimcnhnhau tothnh hthngelectron pgiitoutrn ton bphn t. Vng benzen l mth lin hpbnvngvmt

nhitnghc(nnglngthmha E = 36 kcal/mol).

+

-

+

-

+

-

+

-+-


4/17

Phn ng th electrophin vng benzen (SEAr)

Benzen tiu biucho cc hthngthm,cimvcutrc cabenzen thhincc cimvtnh cht:

- Khuynh hng i vo phn ng th chim u th do phn ng th hthnglin hpcboton.

- Khuynh hngivo phnngcnggimdo phnngcnghthnglinhpbph v.

Phn ng th electrophin SEAr l phn ng c trng quan trng ca vngbenzen.Phnngtngqut:

xc t c

H

+ E Y

-ss

+

E

+ H Y

Tc nhn electrophin l cation E+hoc phn t E-Y.Cc phn ng th SEAr u cn s c mt ca cc cht xc tc.

Vai tr ca cht xc tc l lm tng qu trnh to tc nhn electrophin.


5/17

C ch phn ng th SEAr

Phnngxyra theo 2 giai on:Giai on1: Tc nhn electrophin tncng vo h thngelectron pcanhn thm

tothnh mtphcp; tipphcpchuynthnh phcs:

E

(tr ng th i chuyn tip)

E

phc p phcs

HE

+

Giai on2: phcsl mtcation khng bnvi4 electron pgiitontrn 5 nguyntC; nguyn tC thsu cavng lin ktviE trngthi lai ha sp3. Phcscbnha theo 2 cch:

+ Cnganion Y-tothnh hthngvng xiclohexadien (tosnphmcng)+ Tch proton tolihthngelectron pcavng thm(tosnphmth).

H

H

E

Y(sn phm cng)

E

1.(+ Y )

2.(- H )

(sn phm th)phcs

HE

+

Khuynh hngtch proton H+c u tin hndo c mc nnglngthphn.


6/17

Mt s phn ng th SEAr

Halogen ha

Benzen

Br2/FeBr3

Brom benzen

Br

+ HBr

Br2 + FeBr3 Br + [FeBr4]C ch:

+ H+Br

Br

phc p phc s

HBr

+

Br

Nitro ha C ch:

Benzen Nitro benzen

NO2

+ H2OHNO3/H2SO4

HNO3 + H2SO4 NO2 + 2HSO4 + H2O

NO2

N

O

O

+ N

O

O

HSO4-

phc p phcs

+

HNO2

Sunfo ha C ch:

+ H2O

Axit benzensunfonic

SO3H

Benzen

H2SO4

H2SO4 SO3 + H3O + HSO4

O+ S

O

O

-s:

:

:

:

:

:

:

s+

-s

-s

SO3

phc s

+

HSO3

HSO4

SO3H

H+


7/17

Mt s phn ng th SEAr

Ank yl ha theoFriedel-Crafts

C ch:

+ R - X

Benzen(R : gc ankyl X : halogen) Alkyl benzen

R

AlX3khan

R X AlX3..........s+

s-

R

+ H - X + AlX3AlX4+

RH

R - X + AlX3 R X AlX3..........s+

s-

Dng ankyl halogenua lm tc nhn ankyl ho

di s c mt ca cht xc tc Liuyt:

C ch:Ax yl ha theo

Friedel-Crafts

+ HX

Benzen(R : gc ankyl X : halogen)

+ X - C - R

O

AlX3khan C R

O

Aryl alkyl xeton

s+

s-

R - C - X + AlX3

O

R C O AlX3.....

X

::

C

+ H - X + AlX3

s+

s-

R C O AlX3.....

X

:

:

R O

+

CH

O

R

AlX4

Tc nhn axyl ha thng dng l cc axylhalogenua RCOX hoccc anhydrit axit (RCO)2O:


8/17

Quy lut th SEAr

1. nh hng ca nhm th n s th SEAr:

Mt nhm th R c sn nhn thm c nh hng n v tr ca cc nhmvo sau gi l nhm nh hng.

xc t c

R

+

R

E E

Sdnhvyl:

+ Khi benzen chab th,mtelectron 6 nguyn tC trong vng lnhnhau vo chthu cmtsnphmkhi thlnu.

+ Khi th lnthhai, nhm thmic thnhhngvo cc v tr ortho,metavpara so vinhm nhhng,sthu cmthnhp3 snphmngphn c tlphntrmkhc nhau.


9/17

Quy lut th SEAr

Khi nhn thmc snmtnhm th:Da trn c s tc dng nh hng ngi ta chia lm 2 loinhm th: Nhm thloiI:Tc dngnhhngnhm thvo sau utin vo vtr ortho vparaso vinhm thnhsn; ngthias cc nhm thny kch hots th: gm cc nhm thhotha nhn thm(O-, -NR2, NH2, -OH, -OR, -NHCOCH3, -CH3, -C(CH3), C6H5-) v mtsnhm thphnhotha nhn

thm(halogen, -CH2Cl,) Nhm thloiII:Tc dngnhhngnhm thvo sau utin vo v tr meta so vi nhm th nh sn; ng thi ccnhm th ny th ng ha s th: gm cc nhm th phnhotha nhn thm(-NO2, -NR3, CF3, -CN, -COOH, -COOR, -SO3H, -SO2R, -CHO, -COR.)

ortho

para

I

meta

II

OCH3

ortho ortho

para

Loi I

CH3

ortho ortho

para

Loi I Loi I I

NO2

meta

V d:


10/17

Quy lut th SEAr

Kh i nhn thmc snnhiunhm th:Trnghp nhn thm c snnhiunhm th th v tr nhm thvo sau c

quytnhbinhm thc tc dngnhhngmnhhn.

Trnghpnhm thnhsncng loi:Davo thcnghimlpctrttnhhngcc nhm thnhsncng loitheo dy sau:

Nhm thloiI:

O-> -NR2> -NHR > NH2> -OH > -OR > -NHCOR > halogen (F > Cl > Br > I) >> - OCOR > - R > -ankenyl

Nhm thloiII:-NO2> -NR3> -CN > -COOH > -COOR > -SO3H > -CHO> -COR

OCH3

Loi I

ClLoi Iortho

para

Loi I I

NO2

COOH

meta

Loi I IOCH3

Loi I

CH3Loi I

para

ortho

V d:


11/17

Quy lut th SEAr

Trng hp nhm th nh sn khc loi:Trng hp nhm th nh sn khc loi: nhm th loi I ng vai tr

nhhngnhm thvo sau.

V d:

NO2

NHCOCH3

Loi I

Loi I Iortho

para

COOH

Loi I I

ClLoi Iortho

para

ortho

para

Loi I

OH

SO3H

Loi I I

NO2

CH3

Loi I

Loi I I

ortho

para

CH3

Loi I

NO2Loi I I

para

CH3

Loi I

NO2Loi I I

Tuy nhin quy lut thchc tnh tngiv ngoi yu tin tcn phthuc vo cc yu t khng gian, iu kin phn ng, bn cht ca nhm

th


12/17

Gii thch quy lut th SEAr

Quy lut thcxy dng trn cs thcnghim. Tuy nhin c thgiithch quy lutthdatrn csyutintv nghc.

Tuthucvo bnchtnhm thm mtelectron vng tngln hocgimi,do khnngphnng thSEAr sddng hnhockh hnkhikhng c nhm th.

Phn loinhm thnhvng:Nhm thhotha nhn thm:gmcc nhm ththhincc hiung

dng(+C, +I, +H) yelectron vo vng lm tngkhnngtham gia phnngSE cavng benzen thunlicho phnngSEAr.

V d: cc nhm thO-, -NR2, NH2, -OH, -OR > -NHCOR

Nhm thphnhotha nhn thm:gmcc nhm th thhincchiungm (-C, -I) ht electron vo vng lm gimkhnngtham gia phnng

SEcavng benzen kh khncho phnngSEAr.V d: cc nhm thNO2, COOR, -CN

Trnghpnhm thc cc hiungI v C tc dngtheo chiuhngngcnhau(v dhalogen, -OH, -NR2(-I, +C) th davo trsscaphngtrnh Hammet: cc halogen c trsHammet sdngth phnhothanhn thm,cn nhmOH, -NR2c trssm th hotha nhn thm.


13/17


trngthi tnh(trngthi cbn)

Nhm thnhsnloiI c hiung+I, +C: yelectron vo vng. Do slin hpelectron trong vng nn cc vtr orthovparamtelectron tnghn:

ortho

para

I I

-

-

-

III

Nhm thnhsnloiII c hiung-I, -C : ht electron tvng ra. Do s lin hpelectron trong vng nn cc vtr orthovparaxuthinintch dng,vtr metacintch dngnhnht:

meta

II

II II II II

Nhm thc hiung-I, +C(v dcc halogen F, Cl, Br, I) ht electrontvng ra lm xuthinin tch dng lnnhtv tr orthov para

nn tc nhn electrophin utin vo vtr meta (l vtr c intch dngnhnht.

(X: halogen)

:

X


14/17


trngthi ng

Tc nhn electrophin tn cng to phcs. Nu vng benzen c sn mtnhm thY th c 3 phnngcnhtranh nhau vo cc vtr ortho, meta,para.V vycnxt mcnnglngcaphcsdo phnngsutin tao phccnnglngthphn.

Do phcs l mt tiu phn giu nng lng nn mc nng lng ca ncng thpnuintch dnggiitocng nhiu. Bnchtcanhm thnh

snY ngvai tr lntrong vicgiitointch dngtrn phcs.

ortho

para

Y

E+meta

so

sm

Y

E

H

Y

EH

sp

YH

E

+

+

+


15/17


trngthi ng

Y l nhm thloiI (c hiung+I, +C):gy hiungdngyelectron vo vng

benzen lm gimintch dngtrn phcs, cbitgimnhiucc phcsov spdointch cahai phcnmgnnhm thY nhtv nnglnghotha cc phcso v spnhNhm thE utin vo vtr orthovpara.

Y l nhm th loi II (c hiu ng -I, -C): gy hiu ng m ht electron ca vngbenzen, v thkhng nhnggiitointch dngm cn lm tngintch dngcaphcs, m tngnhiunhtphcsov sp(do intch dngcahai phcnmgn

nhm thY nht). vtr metakhng nhvynn nnglnghotha caphcspnhhnNhm thE utin vo vtr meta.

ortho meta

+

o p m>=

Y

H

E

EH

Y

+

para

+

E

H

Y

(Y: nhm thlo i I I)

Y

(Y: nhm thlo i I)

Y

ortho meta

+

Y

H

E

EH

Y

+

para

E

H

Y

+

o p m


16/17


trngthi ng

Y l nhm thc hiung-I, +C nhhalogen:

trngthi ngphcsc tnh electrophin mnh, l mththiuhtelectron, dosc mtcacpelectron chasdng lun chimu thnn halogen thhinhiung+C> -I, chyuyelectron vo vng benzen nhcc loinhm thloi I khc. Do trng thi ng (phcs) l giai onquytnhcaphnngnn

halogen tuy l nhm thphnhotha nhn thmnhngvnu tin nhhngvo cc vtr orthovpara.

ortho meta

+

o p m


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