第六章熱力學穩(wěn)定性離域能芳香性

電子

波函

??自由熱力學穩(wěn)熱力學穩(wěn)定性—離域能,芳香動力學穩(wěn)定性—反應

nc2

Coefficientof幾率rthAOinth幾率占據軌道

ψ2=0.6015φ1+0.3717φ2-0.3717φ3-ψ1=0.3717φ1+0.6015φ2+0.6015φ3+例如ρ32×(0.6015)22×(-ProbabilityoffindingelectronProbabilityoffindingelectronatom3Probabilityoffindingelectronatom3electrondensityofatom6.3ChargeDensitiesandBondChargeDensitiescN/2 N/2 ccqrc

c2

N/ theMOindexforbonding′:theMOindexforanti-bondingTheprobabilityoffindingtherthAOinalloftheMOsisequalto16.36.3ChargeDensitiesandBondChargeForForneutralA.H’s,theelectronchargesonallofcarbonatomsareequaltoForA.H.’s,theenergylevelsoccursinpairs(x).Themolecularorbitalsofeachpairshouldhavetheproperty:c((x))2c((x)) Pijki,j為原子編號

電子鍵的k為大分子軌道編鍵的ψ2=0.6015φ1+0.3717φ2-0.3717φ3-ψ1=0.3717φ1+0.6015φ2+0.6015φ3+ItItreflectstheofthe-bond,thereforecanbecorrelatedtothebondlengths6.3ChargeDensitiesandBond問題引問題引入了共軛等鍵長假計算的鍵長卻是不同20.60210.37220.372310.37210.60220.6023p1220.3720.60220.6020.372p2320.6020.60220.3720.372Therefore,bond1-2ismuchstrongerthanbond3-4,butadieneisoftendenotedas,6.3ChargeDensitiesandBondBondOrdersandBond6.3ChargeDensitiesandBondMoreactivesitesinradicaltype H

HTheabovesitesarealsoactivetomanyionicreactions.Theactivitydifferencesamongtheatomsinamoleculecouldnotbeinterpretedbyelectronchargedistributiondifferences(EqualChargeDensitiesinA.H.)自由FiFmaxj(此式Fmax與Pij都不包含鍵級.有些文獻在這兩項中都包含鍵級j每個鍵的鍵級為1.兩種方法計算出的Fi是一樣的Fmax

3, Pij不含j對 F1=F4=1.732-0.896=F2=F3=1.732-0.896-0.448=Thatiswhy1,4-additionismorefavorablethan1,2-or2,3-additionsSimilarly,innaphthalene,-siteChasthelargestvalueofvalence,sothatthissiteismoreactivethanordersites.

F>定義Fmax=1.732是因為W.E.Moffitt *假想的炔

1967年,C.Finder又提出:假想的炔丙雙自由基中心C的π鍵級為2.828(若加上兩個σ鍵為4.828),這才是C原子的最大成鍵度.不過,為避免 ,人

6.3ChargeDensitiesandBondMolecular

6.4熱力學穩(wěn)Theextrastabilitiesoriginatedfromthe-electrondelocalizationsinsomecyclicconjugatedhydrocarbons.Somearomatic__Someanti-aromaticCriteria:ResonanceEnergy6.4ResonanceRE=E–

Inunitof>0Aromatic,benzene,=0non-aromatic,acyclic<0anti-aromatic,cyclobutadiene,REisdefinedasthedifferencebetweenthe-energyoftherealmoleculeanditsreferenceE n(x 6.4ResonanceInveryearlyworks,thereferencestructureistheseparateddoublebonds(Ethene).Forexample,thereferencestructureforbenzeneisthreeethenemolecules E=ER=RE=6.4Resonance355646Incorrect6.4TheEight-parameter