ACTIVATION PARAMETERS FOR THE REACTION OF AQUOCOBALAMIN (VITAMIN-B12A) WITH SMALL ANIONIC AND NEUTRAL LIGANDS

被引：31

作者：

MARQUES, HM

机构：

来源：

JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS | 1991年 / 02期

关键词：

D O I：

10.1039/dt9910000339

中图分类号：

O61 [无机化学];

学科分类号：

070301 ; 081704 ;

摘要：

From the temperature dependence of the rate constants, activation enthalpies and entropies were determined for the reaction of aquocobalamin (vitamin B12a) with SCN-, S2O3(2-), NO2-, SO3(2-) and HSO3 -(ionic strength, l = 1.0 mol dm-3, KCl). These, and previously determined activation parameters for CN-, HCN, N3- and HN3, demonstrate the very small differences that exist between most small anionic and neutral ligands in their reactions with B12a. Exceptions are CN- and SO3(2-) which have, respectively, anomalously small and large values for DELTA H double-ended-dagger and DELTA S double-ended-dagger. These effects are possibly due to nucleophilic participation of these ligands in the transition state of the reaction.

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页码：339 / 341

页数：3

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