作者:J. William Thorpe、John Warkentin
DOI:10.1139/v73-137
日期:1973.3.15
interaction between nucleophile and carbonyl carbon (bridging) for reaction of conformation-ally-mobile systems. Conformationally-fixed systems, on the other hand, may be affected by such factors. trans,-2-Chloro-4-t-butylcyclohexanone is 61-fold more reactive than the cis-isomer, in the SN2 reaction with acetate. Activation parameters support the conclusion that only those α-halo ketones which are stereochemically
α-卤代酮与乙酸根和叠氮离子的双分子取代反应对空间位阻非常不敏感。1-溴-4,4-二甲基-2-戊酮(溴甲基新戊基酮)的反应性仅略低于溴丙酮,尽管前者中的羰基是新戊基的。结果根据正常的 SN2 过渡态进行解释,不涉及进入和离开基团与羰基功能(共轭)的 π 轨道的特殊排列或亲核试剂与羰基碳(桥接)之间的共价相互作用以进行构象反应-ally-移动系统。另一方面,构象固定系统可能会受到这些因素的影响。在与乙酸盐的 SN2 反应中,反式,-2-氯-4-叔丁基环己酮的反应性比顺式异构体高 61 倍。