COMPLEX-FORMATION REACTIONS OF AQUACOBALAMIN REVISITED - EFFECT OF CHLORIDE ON THE RATE AND ACTIVATION PARAMETERS

被引：27

作者：

PRINSLOO, FF ^{[1
]}

BREET, ELJ ^{[1
]}

VANELDIK, R ^{[1
]}

机构：

[1] UNIV ERLANGEN NURNBERG,INST INORGAN CHEM,D-91058 ERLANGEN,GERMANY

来源：

JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS | 1995年 / 04期

关键词：

D O I：

10.1039/dt9950000685

中图分类号：

O61 [无机化学];

学科分类号：

070301 ; 081704 ;

摘要：

Complex-formation reactions of aquacobalamin were reinvestigated to clarify the role of high chloride concentrations (up to 1 mol dm-3). It was found that high chloride concentrations retard the reactions due to the formation of the less substitution-labile chloro complex, for which the formation constant was found to be 0.8 dm3 mol-1 at 25-degrees-C and ionic strength 1.0 mol dm-3. The pH dependence of the complex formation with hydrazoic acid was also re-examined. Volumes of activation were determined for the reactions with HN3 and N3- in NaClO4 medium and are discussed in comparison with those measured in KCl medium. Direct kinetic evidence for the occurrence of a reverse, acid-catalysed aquation reaction was found and this step is characterised by an activation volume of +8.3 +/- 1.6 cm3 mol-1. The results are all in agreement with the concept of a dissociative interchange substitution mechanism.

引用

页码：685 / 688

页数：4

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