(2―4―OCO 2 Ph) were subjected to solvolysis in the series of aqueous ethanol, the product ratios were determined and the selectivities (k E /k W ) of the corresponding stabilized benzhydrylium ions 1―4 were calculated. The individual rate constants for ethanolysis (k E ) and hydrolysis (k W ) have been calculated. Ethanolysis proceeds via earlier more carbocation-like transition state than hydrolysis. Due
将
碳酸甲酯(1-4-OCO 2 Me)和
碳酸苯酯(2-4-OCO 2 Ph)在一系列
乙醇水溶液中进行溶剂分解,测定产物比和选择性(k E /k W )计算出相应的稳定二苯甲基离子1-4。已经计算了
乙醇分解 (k E ) 和
水解 (k W ) 的各个速率常数。
乙醇分解通过比
水解更早的更类似碳正离子的过渡态进行。由于更重要的溶剂化作用,如果二元溶剂中
水的比例增加,则 k E 下降得比 k W 慢,其净效应是选择性对溶剂极性的显着依赖性。由于 log k 与 E 曲线的配对和弯曲,较不稳定的碳正离子 5-8 的选择性降低并受到离去基团的影响。