Dielectric Relaxation and Complex Formation in Dilute Solutions of Chloroform and Bromoform in Nonpolar Solvents

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Abstract
Measurements of dielectricpermittivity and loss in the microwave region at 20°C have been made on dilute solutions of chloroform and bromoform in cyclohexane, benzene, mesitylene, and 1,4‐dioxane, and on chloroform in 2,5‐dimethylpyrazine. The shortest relaxation times are found in cyclohexane solution and the longest in mesitylene, dioxane, and dimethylpyrazine. For the solutions of chloroform in benzene and mesitylene use of literature values for constants of association allows calculation of the relaxation time of the complex. For the other mixtures a method is proposed for the determination of both the constant of association and the relaxation time of the complex. The relaxation times for the complexes of chloroform with mesitylene, dioxane, and dimethylpyrazine are comparable and can be attributed to rotational reorientation of the complex. A similar conclusion may be drawn for the complexes of bromoform with mesitylene and dioxane. In benzene the relaxation times of the complexes with chloroform and bromoform are too small to be attributed to rotational reorientation and presumably reflect the lifetime of the associated species instead. These conclusions are consistent with the enthalpies of mixing for the above solutions.