Oxidative Deamination and Decarboxylation of L-Asparagine by the Aqueous Alkaline Diperiodatonickelate(IV) Complex
作者:Sanjeevagowda T. Patil、Mahantesh A. Angadi、Abdulazizkhan L. Harihar
DOI:10.1007/s10953-008-9341-8
日期:2008.12
The kinetics of the oxidation of L-asparagine, (L-asp) by diperiodatonickelate(IV), (DPN) in aqueous alkaline medium at a constant ionic strength of 0.5 mol⋅dm−3, was studied spectrophotometrically. The reaction is first order in [DPN] and of fractional order in both [L-asp] and [alkali]. Addition of the products has no significant effect on the reaction rate. However, increasing the ionic strength or decreasing the dielectric constant of the medium increases the reaction rate. The oxidation process in alkaline medium is shown to proceed via two paths, one involving the interaction of L-asparagine with diperiodatonickelate(IV) ion in a slow step to yield the products, and the other path involving the interaction of alkali with the diperiodatonickelate(IV) ion to give nickel(II). Some reaction constants involved in the mechanism were determined, and calculated and observed rate constants are in excellent agreement. The activation parameters were computed for the slow step of the mechanism.
在离子强度恒定为 0.5 mol⋅dm-3 的碱性水介质中,用分光光度法研究了二碘锑镍酸(IV)(DPN)氧化 L-天冬酰胺(L-asp)的动力学。反应在[DPN]中为一阶,在[L-asp]和[碱]中均为分数阶。加入产物对反应速率没有明显影响。然而,增加介质的离子强度或降低介电常数会增加反应速率。碱性介质中的氧化过程有两条路径,一条是 L-天冬酰胺与二碘镍酸(IV)离子缓慢作用生成产物,另一条是碱与二碘镍酸(IV)离子作用生成镍(II)。确定了机理中涉及的一些反应常数,计算出的速率常数与观察到的速率常数非常吻合。计算了该机理慢步的活化参数。