Comparative Study of the Reactivities of Substituted 3-(Benzoyl)benzyl Carbanions in Water and in DMSO
作者:Laura Llauger、Miguel A. Miranda、Gonzalo Cosa、J. C. Scaiano
DOI:10.1021/jo049224g
日期:2004.10.1
thus, intra-SN2 are favored in polar nonprotic solvents, and the effect is larger for the more hindered carbanion centers. Protonation by water is slightly dependent on the nature of the carbanion center and is ∼400 times faster in nonhydroxylic solvents, compared with bulk water. As expected, the reactivity for halide leaving groups follows the usual order of decreasing bond strengths, i.e., I- >
已通过在碱性水溶液和DMSO溶液中对酮洛芬衍生物进行光脱羧而生成的苄基取代的碳负离子进行了研究。产品研究与激光闪光光解的动力学测量相结合,已经确定了质子化和S N 2内反应导致五元和六元环环化的绝对速率常数;前者明显更快。碳负离子反应性的许多众所周知的趋势都是以绝对速率为基础的。因此,内部S N2在极性非质子溶剂中更受青睐,对于受阻更严重的碳负离子中心,效果更大。与大量的水相比,水的质子化在某种程度上取决于碳负离子中心的性质,并且在非羟基溶剂中的质子化速度快约400倍。如所预期的,对于卤化物离去基团的反应性如下降低粘合强度,即,通常的顺序,我- >溴- >氯- 。