作者:Joseph Griffin、John Atherton、Michael I. Page
DOI:10.1002/poc.3148
日期:2013.12
The rates of ammonolysis of alkyl benzoate and phenylacetate esters in liquid ammonia increase with the acidity of the leaving group alcohol and show relatively large Brønsted βlg values of −1.18 and −1.34, respectively, when plotted against the aqueous pKa of the alcohol. The Brønsted βlg obtained using the pKa of the leaving group alcohol in liquid ammonia is significantly reduced to ~ −0.7, which
苯甲酸烷基酯和苯乙酸烷基酯在液氨中的氨解反应速率随离去基团醇的酸度增加而增加,当针对醇的水性pK a作图时,其布朗斯台德βlg值分别为-1.18和-1.34 。所述布朗斯台德β LG使用的pK获得一个在液氨中的离去基团醇的显著减少至〜-0.7,这表明中的限速步骤涉及四面体中间体的具有很少C-OR键裂变在过渡的反应状态。溶剂分解反应会受到铵离子的明显催化,这令人惊讶地产生了类似的布朗斯台德βlg表明铵离子与离去基团之间几乎没有相互作用。结论是,氨离子催化烷基酯在液氨中的溶剂分解的限速步骤是两性离子四面体中间体T +-的扩散控制质子化生成T +,其迅速去质子化生成T 0。这与未催化反应的限速步骤兼容,即通过“质子开关”形成中性T 0。版权所有©2013 John Wiley&Sons,Ltd.