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Istomin和Palm曾提出用模型ΔfH0(RX)=h[R]+h[X]+φ[R]φ[X](式中h[R]和h[X]分别为烷基R和取代基X对单取代烷烃生成焓ΔfH0(RX)的贡献,φ[R]φ[X]则表示R与X之间的相互作用对ΔfH0(RX)的贡献)来表示单取代烷烃生成焓ΔfH0(RX).对于双向延伸化合物R1-Y-R2,其取代基Y位于分子链的中间,与两个烷基(R1和R2)相连.此类化合物分子内取代基与烷基之间的相互作用,较单取代烷烃的相比更为复杂.因此,Istomin-Palm模型在R1-Y-R2体系中应用必须进行修正.本文把取代基Y、烷基R1和R2三者之间的相互作用对R1-Y-R2类化合物生成焓ΔfH0(R1-Y-R2)的贡献分为三部分:R1Y与R2之间的相互作用(φ[R2]φ[R1Y]),YR2与R1之间的相互作用(φ[R1]φ[YR2]),以及两烷基R1与R2之间的相互作用(ψ[R1]ψ[R2]).用以上三项替换φ[R]φ[X],扩展Istomin-Palm模型,建立一个新的经验模型ΔfH0(R1-Y-R2)=h[R1]+h[R2]+h[Y]+φ[R1]φ[YR2]+φ[R2]φ[R1Y]+ψ[R1]ψ[R2],来表示ΔfH0(R1-Y-R2)(式中h[R1]、h[R2]和h[Y]分别为烷基R1、R2和取代基Y对ΔfH0(R1-Y-R2)的贡献,后三项则表示烷基R1、R2和取代基Y两两之间相互作用对ΔfH0(R1-Y-R2)的贡献).进而,采用本研究组最近报道的相互作用势指数IPI(X)(Wu,Y.X.;Cao,C.Z.;Yuan,H.Chin.J.Chem.Phys.2012,25(2),153.)表示取代基Y对烷基的固有作用(φ[Y]),从而建立两个定量估算生成焓的通用模型.其中,一个用于估算硫醚、仲胺、醚和酮类化合物生成焓,另一个用于估算酯类化合物生成焓.这两个模型均得到良好的结果,与采用G3和G3MP2方法相比具有同样的精度,还可以避免大量繁琐的计算.
Istomin and Palm proposed to use the model ΔfH0 (RX) = h [R] + h [X] + φ [R] φ [X] where h [R] and h [ The contribution of the monosubstituted alkane formation enthalpy, ΔfH0 (RX), and φ [R] φ [X], which represents the contribution of the interaction between R and X to ΔfH0 (RX) In the case of the birefringent compound R1-Y-R2, the substituent Y is located in the middle of the molecular chain and is linked to two alkyl groups (R1 and R2), and the interaction between the substituents and the alkyl groups in such compounds, Therefore, the application of Istomin-Palm model in R1-Y-R2 system must be modified.In this paper, the interaction between the substituents Y, alkyl groups R1 and R2 on R1 The contribution of the formation enthalpy ΔfH0 (R1-Y-R2) of the -Y-R2 compounds is divided into three parts: the interaction between R1Y and R2 (φ [R2] φ [R1Y]), the interaction between YR2 and R1 (φ [R1] φ [YR2]) and the interaction between two alkyl groups R1 and R2 (ψ [R1] ψ [R2]). -Palm model to establish a new empirical model ΔfH0 (R1-Y-R2) = h [R1] + h [R2] + h [Y] + φ [R1] φ [YR2] + φ [R2] ] + ψ [R1] ψ [R2] to indicate ΔfH0 (R1- Y-R2) where h [R1], h [R2] and h [Y] are the contributions of alkyl groups R1, R2 and substituent Y to ΔfH0 (R1-Y-R2), respectively, The contribution of the interactions between the two groups R1, R2 and Y to the ΔfH0 (R1-Y-R2) is further investigated by using the recently reported potential potentials IPI (X) (Wu, YX; Cao , CZ; Yuan, H. Chin. J. Chem. Phys. 2012, 25 (2), 153) represents the intrinsic effect of the substituent Y on the alkyl group (φ [Y]) establishing two quantitatively estimated enthalpies of formation , One of which is used to estimate the enthalpies of formation of thioethers, secondary amines, ethers and ketones and the other to estimate the enthalpy of formation of esters. Both models yielded good results, in contrast to those using G3 and G3MP2 Compared with the same accuracy of the method, but also to avoid a lot of tedious calculations.