第四级铵氢氧化物的Hofmann消除反应的研究——关于Hofmann消除反应的构象规则

A Study of the Thermal Elimination of Quaternary Ammonium Hydroxides——On the Conformation Rule for Hofmann Elimination

第四级铵氢氧化物的热消除反应并不都遵循Hofmann规则,为此文献(2)提出了一个消除反应的构象规则,为了检验这两个规则的适应性和可靠性,本文研究了八个可用于对比的第四级铵氢氧化物的热消除反应,结果表明构象规则远比经典的Hofmann规则优越。

It is known that there are many examples of the thermal elimination of quaternary ammonium hydroxides which do not follow the Hofmann rule. Based On the expermental data reported in the literature, Ye, one of us, and Zhu found that the orientation of the elimination reaction is chiefly determined by the preferential. con-formation of the reactant rather than by the acidity of the β-hydrogen atoms of the alkyl groups and a "conformation rule" was proposed for the elimination of quaternary" ammonium hydroxides[ 2 ]. However, when these two rules, the classical Hofmann rule and the conformation rule, are cmployed, one occasionally gets different or even contradictory predictions. In order to contrast the two lulcs one with the other in their reliabilities, eight quaternary ammonium hydroxides were prepared and subjected to the elimination reaction. The experimental results obtained ( shown in Table 1 ) are all in good agreement with the conformation rule, but only partially with the Hofmann rule, in other words, the conformation rule is superior and acceptable.