Kinetics and Mechanism of Pyridinolysis of Aryl Dithiocyclopentanecarboxylates in Acetonitrile

Bulletin of the Korean chemical society

Hyuck Keun Oh¹ 

关键词: Nucleophilic substitution reaction;    Pyridinolysis;    Cross-interaction constant;    Zwitterionic tetrahedral intermediate;    Stepwise mechanism;   

DOI  :  

学科分类：化学（综合）

来源: Korean Chemical Society

【 摘 要 】

Kinetic studies on the pyridinolysis of aryl dithiocyclopentanecarboxyaltes 2 were carried out at 60.0 ^oC in acetonitrile. In the aminolysis of 2, the �?_X values were 0.5 - 0.8 with anilines, and there was no breakpoint. However, in the pyridinolysis of 2, biphasic Brönsted plots were obtained, with a change in slope from a large value (�?_X ≠ 0.7) to a small value (�?_X ≠ 0.4) at pK_a⁰ = 5.2. This was attributed to a change in the rate-limiting step from breakdown to the formation of a zwitterionic tetrahedral intermediate, T^�?, in the reaction path, with an increase in the basicity of the pyridine nucleophile. An obvious change in the cross-interaction constant _ヱXZ from a large positive (_ヱXZ = +1.02) value to a small negative value (_ヱXZ = -0.17) supports the proposed mechanistic change.

【 授权许可】

Unknown