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对于简单饱和烃及其衍生物来说,其构象异构体的焓值和焓差,可借助于正丁烷作近似计算.正丁烷的顺、反交叉式构象异构体如图1所示,反交叉式为优势构象,顺交叉式存在构象对映体.反交叉式中两个甲基之间不存在非键联作用,而顺交叉式中两个甲基之间的非键联作用数为1,即两种极限构象之间的作用数之差为1.已知每一歪扭作用的△H=
For simple saturated hydrocarbons and their derivatives, the enthalpy and enthalpy difference of their conformers can be approximated by means of n-butane. The cis- and trans-conformers of n-butane are shown in Figure 1 The antisocross type is the conformational conformer, and the conformational enantiomer is cis-crossover type. There is no non-linkage between the two methyl groups in the antisoccipital type, while the non-linkage between the two methyl groups in the cis- The action number is 1, ie, the difference in the number of actions between the two ultimate conformations is 1. It is known that each skew function has a ΔH =