Competing solvolytic substitution and elimination reactions via a common irreversibly formed ion-molecule pair intermediate
作者:Harvinder Sidhu、Alf Thibblin
DOI:10.1002/poc.610071009
日期:1994.10
carbocation–molecule pair (with a secondary isotope effect of 1·54), which either undergoes nucleophilic attack by a solvent molecule (with a secondary isotope effect of ca 1), or is dehydronated (isotope effect ca 2·8) by the leaving group or by the solvent. The ion-molecule pair shows very low selectivities. Thus, in 50 vol.% acetonitrile in water, an acetonitrile molecule is as efficient as a water molecule as a
在25°C下水与乙腈或甲醇的混合物中9-(2-苯氧基-2-丙基)芴经酸催化的溶剂分解可提供9-(2-羟基-2-丙基)芴,9-(2-丙烯基) )芴和9-(2-乙酰胺基-2-丙基)芴或9-(2-甲氧基-2-丙基)芴。总动力学氘同位素效应为六氘类似物9-(1,1,1,3,3,3-的反应2 ħ 6)-9-(2-苯氧基-2-丙基)芴在90体积%的水中乙腈的测量结果为(k + k)/(k + k)= 1·54±0·05,它由同位素效应k / k = 1·4±0·1组成,用于形成取代产物和k /用于生产9-(2-甲氧基-2-丙基)芴的k= 4·0±0·2。在其他溶剂混合物中也测得了类似的同位素效应。结果有力地表明了一种分支机制,该机制涉及限速形成一个常见的碳正离子-分子对(次级同位素效应为1·54),该对偶合分子会受到溶剂分子的亲核攻击(次级同位素效应为ca 1)。 ,或通过离去基团或通过溶剂脱氢(同位