Deuterium and oxygen-18 isotope effects on nucleophilic displacement by monomeric water in aprotic solvents
作者:Joseph L. Kurz、Jasun Lee
DOI:10.1021/ja00536a068
日期:1980.7
for nucleophilic attack by water at a methyl carbon (eq 1) is reduced to very near unity when the water is a dilute solute in L/sub 2/O+CH/sub 3/X..-->..L/sub 2/O/sup +/CH/sub 3/+X/sup -/ a dipolar aprotic solvent. This effect was observed for three leaving groups (CH/sub 3/X equals 1-methylthiophenium ion (MeTh/sup +/), methyl perchlorate (MeOCl/sub 3/), and methyl trifluoromethanesulfonate (MeOTf))
当水是 L/sub 2/ 中的稀溶质时,水在甲基碳上亲核攻击的 H/sub 2/O/D/sub 2/O 速率常数比(方程 1)降低到非常接近统一O+CH/sub 3/X..-->..L/sub 2/O/sup +/CH/sub 3/+X/sup -/ 偶极非质子溶剂。对于三个离去基团(CH/sub 3/X 等于 1-甲基噻吩鎓离子 (MeTh/sup +/)、高氯酸甲酯 (MeOCl/sub 3/) 和三氟甲磺酸甲酯 (MeOTf))和两种非质子溶剂观察到这种效应乙腈 (MeCn) 和四氢噻吩 1,1-二氧化物 (TMSO:'';环丁砜)。还观察到,对于 MeTh/sup 的反应,相应的 H/sub 2//sup 16/O/H/sub 2//sup 18/O 速率常数比为 1.002 ± 0.004(95% 置信限) +/ 在 35/sup 0/C 下在 TMSO/sub 2/ 中稀释 H/sub