烷基电子效应的再认识

烷基的电子效应尽管因其所连环境的不同而有异,但是认为烷基此一时是给电子的诱导效应,彼一时又是吸电子的诱导效应,以及认为烷基的超共轭效应仅存于溶液体系中是站不住脚的。本文作者认为,烷基在不带电荷的中性有机结构中,通过诱导效应总是吸电子的,但当它与不饱和结构,包括带正电荷的原子或原子团相连时,还通过Baker—Nathan超共轭效应,乃至空间超共轭效应起供电作用。只是这种供电作用,在溶液中,由于溶剂化作用,其相对强弱遵循Baker—Nathan顺序;而在气相或溶剂化作用很小的溶液中则遵循反Baker—Nathan顺序.

REMARKING AGAIN ON ELECTRONIC EFFECTS OF AN ALKYL GROUP

Although the electronic effects of an alkyl group vary with the circumstances concerned, it does not hold water to consider that an alkyl group is an electron-withdrawing group by inductive effect at one time,an electrondonating group at another time,and hyperconjugation lies only in solution. In this paper we hold that an alkyl group is an electron-withdrawing group by inductive effect when it is connected to a saturated system,but it is an electron-donating group when it is connected to an unsaturated system or an atom having a positive charge by hyperconjugation, and even space-h yperconjugation. However, the relative strength of these electron donors follows the Baker-Nathan order by solvation effects in solution, and the Baker-Nathan anti-order in gas phase.