Department of Chemistry and Biochemistry, University of Oklahoma, Norman, Oklahoma 73019, USA.
J Phys Chem B. 2009 Dec 17;113(50):16118-23. doi: 10.1021/jp907018s.
The temperature dependence of the dielectric rate constant, defined as the reciprocal of the dielectric relaxation time, is examined for several groups of organic solvents. Early studies of linear alcohols using a simple Arrhenius equation found that the activation energy was dependent on the chain length of the alcohol. This paper re-examines the earlier data using a compensated Arrhenius formalism that assumes the presence of a temperature-dependent static dielectric constant in the exponential prefactor. Scaling temperature-dependent rate constants to isothermal rate constants so that the dielectric constant dependence is removed results in calculated energies of activation E(a) in which there is a small increase with chain length. These energies of activation are very similar to those calculated from ionic conductivity data using compensated Arrhenius formalism. This treatment is then extended to dielectic relaxation data for n-alkyl bromides, n-nitriles, and n-acetates. The exponential prefactor is determined by dividing the temperature-dependent rate constants by the Boltzmann term exp(-E(a)/RT). Plotting the prefactors versus the static dielectric constant places the data on a single master curve for each group of solvents.
介电率常数的温度依赖性，定义为介电弛豫时间的倒数，在几种有机溶剂中进行了研究。早期使用简单的阿仑尼乌斯方程对线性醇的研究发现，活化能取决于醇的链长。本文使用补偿阿仑尼乌斯形式主义重新检查了早期的数据，该形式主义假设指数前因子中存在与温度相关的静态介电常数。将与温度相关的速率常数缩放到等温速率常数，从而消除介电常数的依赖性，得到计算的活化能 E(a)，其中随着链长的增加略有增加。这些活化能与使用补偿阿仑尼乌斯形式主义从离子电导率数据计算得到的活化能非常相似。然后将该处理方法扩展到 n-烷基溴化物、n-腈和 n-乙酸酯的介电弛豫数据。指数前因子通过将与温度相关的速率常数除以玻尔兹曼项 exp(-E(a)/RT) 来确定。将前因子与静态介电常数作图，可将每组溶剂的数据置于单个主曲线上。
