离子对的聚集作用(Ⅰ)——溶剂和卤负离子对聚集度的影响

AGGREGATION OF ION PAIRS (Ⅰ)——SOLVENT AND ANION EFFECT ON THE AGGREGATION

用沸点升高法测定了卤化四丁铵在有机溶剂中的平均聚集度。发现溴化四丁铵在苯中的聚集度远大于在氯仿中的。说明溶剂的极性起着首要作用。在氯仿中聚集度的大小顺序为碘化四丁铵>溴化四丁铵>氰化四丁铵。 还测定了溴化与碘化四丁铵混合溶液的聚集度。测得值显著大于它们单独存在时的值。认为存在离子对的渔合聚集体。

The average aggregation number (A) of tetrabutylammonium halides in organic solvent has been determined ebulliometrically. A of tetrabutylammonium bromide in benzene is much larger than that in chloroform (Fig.1), it seems that the polarity of the solvent is the major factor.In chloroform, A decreases in the order. iddide>bromide>chloride (Fig.2).When the quaternary ammonium salts exist as mixtures under phase-transfer reaction conditions, and A of the mixed bromide and iodide is determined and is found larger than each alone when there were no interaction between different ion pairs. We consider the ion pairs existing as mixture aggregate (see Table).