12. 水-有機溶媒系中でのチオール類の超音波化学反応への不均一性の影響

概要

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Thiols are well known to be oxidized by ultrasonic irradiation in an aqueous solution. In order to clarify the effects of heterogeneity on sonochemical reactions in liquid-liquid systems, disappearance reactions of thiols were studied in some water-organic solvent systems. In a c-hexane/water system, the rate constants of sonochemical disappearance reactions of alkyl thiols with long carbon chains, alkyl thiols with short ones, and p-toluene thiol were decreased in this order (Fig.2). However, in a di-i-propyl ether/water system, the order was reversed (Fig.3). In i-propanol/water systems, the rate constants of sonochemical disappearance reactions depended on the content of water and chemical structures of thiols. As shown in Fig. 4 and 5, the rate constants of alkyl thiols with short carbon chains were steeply increased as the content of water went up to over 3:8 (i-propanol:water), while that of p - toluene thiol was slowly increased. From these studies, it is concluded sonochemical organic reactions in liquid- liquid systems more greatly depend on the heterogeneity and chemical structures of substrates compared to homogeneous organic reactions.
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