Secondary α-deuterium kinetic isotope effects in solvolyses of 2-cyclopentylethyl, 2-(Δ2-cyclopentenyl)ethyl and 2-(Δ3-cyclopentenyl)ethyl p-nitrobenzenesulphonates
作者:C.C. Lee、E.W.C. Wong
DOI:10.1016/s0040-4020(01)82225-0
日期:1965.1
considerable SN2 character for the solvolysis of this sytem. Small but appreciable isotope effects were noted for II and II-d2. Solvolyses of III and III-d2 showed the highest isotope effects, kH/kD for acetolysis being about 1·14. This value is much less than an expected rate retardation of about 15% per α-deuterium atom for acetolysis with a limiting or SN1 mechanism. The results are interpreted as
2-环戊基乙基的溶剂分解的动力学,2-(Δ 2 -cyclopentenyl)乙基和2-(Δ 3 -cyclopentenyl)乙基p -nitrobenzenesulphonates(I,II和III,分别地)和相应的1,1-二-氘化在25%的水-75%的二恶烷和冰醋酸中的许多温度下研究了类似物Id 2,II-d 2和III-d 2。对于I和Id 2观察到的非常小的k / k D值表明该系统的溶剂分解具有相当大的S N 2特性。注意到II和II-d 2的同位素效应很小,但可观。III和III-d的溶剂2显示出最高的同位素效应,乙酰分解的k H / k D约为1·14。该值远小于通过限制性或S N 1机理进行乙酰分解的预期的每个α-氘原子约15%的速率延迟。该结果被解释为与Streitwieser的假设一致,即邻近小组参与速率确定步骤将降低α-氘动力学同位素效应的幅度。对活化参数的考虑表明