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CHNG 8: PHNG PHP HUCKEL N GIN V CC NG DNGTRNG I HC QUY NHNKHOA HA HCHA HC LNG T HIN IPhm Minh HongNguyn Th Ngc SngNguyn Minh NhtNhm:NI DUNG CHNH- Xc nh nng lng ca cc AO ca phn t theo phng php HMOCch tm hm sng ca h suy binXy dng gin phn t - p dng ca phng php HMO m rng vi cc phn t d vng thm Tm quan trng ca tnh i xngM Uu nhng nm 1930 Huckely xy dng m t mt phng php ha hc lng t n gin. Mt trong nhng th mnh ca phng php ny l nh s gn ng v n gin ca n, nh hng ca tnh i xng v cu trc lin kt trn cc c im phn t.Ngoi ra, s n gin ca m hnh lm cho n mt cng c ging dy cho vic minh ha nhiu khi nim ha hc lng t, nh bc lin kt, mt electron v nng lng AO. Thit lp nh thc HMO

Gc t do allyl

x=(-E)/

Hnh 8-4: Cu hnh -electron v tng s nng lng cho cc trng thi c bn ca cc cation, gc, anion allyl.8.16

Hm sng MO h allylHnh 8-5: MO h allyl. H xyclopropenyl: Cch gii suy bin

Vi x = -2 th gii c hm sng 1

Vi x = 1 th gii tm hm sng 2,3

33Kim tra iu kin trc giao 2, 3

Vi Hnh 8-7: HMO cho h cyclopropenyl: (a) 1 = (1/3)(X1 + X2 + X3); (b) 2 = (1/2)(X1 - X2) (c) 3 = (1/6)(X1 + X2 2X3).

S phn b in tch theo phng php HMO Mt electron (qr) v bc lin kt (prs)

Trong : qrs: bc lin kt (s lin kt) gia hai nguyn t r, s cnh nhauni: s electron c trong MO icir (cir): h s t hp ca AO nguyn t r (nguyn t s) trong hm MO i (xc nh theo hng ngang trong ma trn h s) M rng vi cc phn t d vng

BNG 8-3 Cc thng s nguyn t d vng trong HMO

Cc ch s phm ng HMOCh s ha tr t do (Fr)Trong : Fr: ch s ha tr t do ca nguyn t r trong phn tqrs: bc lin kt (s lin kt) gia hai nguyn t r, s cnh nhau

Gin phn t