Kinetics of the Exchange of Hydrogen between Phosphine and Water: A Kinetic Estimate of the Acid and Base Strengths of Phosphine1
Kinetics of the Exchange of Hydrogen between Phosphine and Water: A Kinetic Estimate of the Acid and Base Strengths of Phosphine1
复制标题
膦与水之间氢交换的动力学：膦酸和碱强度的动力学估计1
DOI：
10.1021/ja01640a072
复制
发表时间：
1954
影响因子：
15
通讯作者：
J. Bigeleisen
中科院分区：
文献类型：
--
作者：
R. E. Weston;J. Bigeleisen
通过跟踪磷化氢中氘的吸收来测量磷化氢和含有3%氘的水之间的氢交换接近平衡的速率。在从气相到液相的扩散不是速率决定因素的情况下，交换分数作为时间的函数遵循通常的麦凯速率定律。速率表达式可以写为 d (PH2D)/dZ=(PH3){2¡* haí (HA¡)+ &oh~(OH~)) 其中 HA¡ 代表具有可交换质子的一般酸。通过对速率常数做出合理的假设，磷化氢在水中的基本解离常数估计为 10-28。对酸解离常数也进行了类似的估计，为 10-29。 作为涉及稳定同位素的反应总体研究计划的一部分，我们最近报告了对磷化氢和水之间氢交换平衡的研究。 2 从达到这种平衡所需的实验条件来看，膦显然表现为弱碱。由于文献中没有关于膦碱性的报道（除了它比其类似物氨弱得多这一事实之外），因此对交换机制进行了动力学研究，目的是确定水溶液中膦的酸和碱性质。所使用的同位素交换方法似乎普遍适用于其他弱酸和弱碱的研究。
The rate of approach to equilibrium in the hydrogen exchange between phosphine and water containing 3% deuterium has been measured by followingthe uptake of deuterium in the phosphine. Under conditions where the diffusion from the gaseous to the liquid phase is not rate-determining, the fraction of exchange as a function of time follows the usual McKay rate law. The rate expression may be written as d (PH2D)/dZ=(PH3){2¡* haí (HA¡)+ &oh~(OH~)) where HA¡ represents a general acid with exchangeable proton. By making reasonable assumptions concerning rate constants, an estimate of 10-28 is made for the base dissociation constant of phosphine in water. A similar estimate of 10-29 is made for the acid dissociation constant.As part of a general program of research on reac-tions involving stable isotopes, we have recently re-ported an investigation of the equilibrium in the exchange of hydrogen between phosphine and wa-ter. 2 Fromthe experimental conditions required to attain this equilibrium, it was evident that phos-phine was behaving as a weak base. Since nothing had been reported in the literature on the basicity of phosphine (other than the fact that it is consider-ably weaker than its analog, ammonia), a kinetic investigation of the exchange mechanism was un-dertaken, with the object of determining something about the acid and base properties of phosphine in aqueous solution. The method of isotopic ex-change which was used appears to be generally ap-plicable to studies of other weak acids and bases.