第六章热力学稳定性离域能芳香性

电子

波函

••自由热力学稳热力学稳定性—离域能,芳香动力学稳定性—反应

nc2

Coefficientof几率rthAOinth几率占据轨道

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为原子编号

电子键的k为大分子轨道编键的ψ2=0.6015φ1+0.3717φ2-0.3717φ3-ψ1=0.3717φ1+0.6015φ2+0.6015φ3+ItItreflectstheofthe-bond,thereforecanbecorrelatedtothebondlengths6.3ChargeDensitiesandBond问题引问题引入了共轭等键长假计算的键长却是不同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与Pij都不包含键级.有些文献在这两项中都包含键级j每个键的键级为1.两种方法计算出的Fi是一样的Fmax

3, Pij不含j对 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>定义Fmax=1.732是因为W.E.Moffitt *假想的炔

1967年,C.Finder又提出:假想的炔丙双自由基中心C的π键级为2.828(若加上两个σ键为4.828),这才是C原子的最大成键度.不过,为避免 ,人

6.3ChargeDensitiesandBondMolecular

6.4热力学稳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