REACTION OF THIOLS WITH ACETYLIMIDAZOLE - EVIDENCE FOR INDEPENDENT REACTION PATHWAYS
REACTION OF THIOLS WITH ACETYLIMIDAZOLE - EVIDENCE FOR INDEPENDENT REACTION PATHWAYS
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DOI：
10.1021/ja00735a017
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发表时间：
1971-01-01
影响因子：
15
通讯作者：
SALVESEN, K
中科院分区：
文献类型：
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作者：
JENCKS, WP;SALVESEN, K
随着咪唑缓冲液浓度的增加，乙酰基咪唑与弱酸性硫醇的反应的速率控制步骤发生变化。咪唑催化的步骤被分配到四面体加成中间体的分解和其他步骤的巯基阴离子的攻击上的自由乙酰咪唑。然而，同时，乙酰基咪唑离子与硫醇阴离子的非催化反应不经历这种变化的速率决定步骤。磷酸盐催化的反应也不经历速率决定步骤的变化，并且在咪唑不引起进一步速率增加的条件下，磷酸盐可以引起速率增加。有人建议，这些结果可以解释在水溶液中的双分子反应，进行独立的，并行的途径，即中间体或过渡态不需要是atequi-liquidation相对于运输过程。
The reactions of acetylimidazole with weakly acidic thiols undergo a change in rate-determining step with increasing imidazole buffer concentration. The imidazole-catalyzed step is assigned to the breakdown of a tetrahedral addition intermediate and the other step to attack of thiol anion on free acetylimidazole. However, the concurrent, uncatalyzed reaction of acetylimidazolium ion with thiol anion does not undergo this change in rate-determining step. The phosphate-catalyzed reaction also does not undergo a change in rate-determining step and phosphate can bring about a rate increase under conditions in which imidazole brings about no further rate increase. It is suggested that these results may be explained in terms of bimolecular reactions in aqueous solution that proceed by independent, concurrent pathways; ie, the intermediates or transition states need not be atequi-librium with respect to transport processes.