Abstract 4-Hydroxy-2-butanone as important chemical intermediate in the field of both pharmaceutical and food industries is traditionally synthesized from formaldehyde and acetone via aldol reaction with relatively low selectivity due to the heavy side reactions. Herein, series of basic ionic liquids with different sterically hindered cations were prepared for this reaction process. The catalytic performance evaluation results revealed the selectivity of 4-hydroxy-2-butanone could be enhanced with the extension of alkyl chain length substituted in the cation of ionic liquid and increasing number of substituted alkyl group. And the tetraoctyl ammonium hydroxide ([N8,8,8,8]OH) was identified as the optimal ionic liquid catalyst with selectivity of 91.1% toward 4-hydroxy-2-butanone at 40 °C. The kinetic studies indicated the formation of 4-hydroxy-2-butanone was first-order dependent on both acetone and formaldehyde concentrations, with the lowest activation barrier of 49.8 kJ/mol among all steps.

中文翻译：

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离子液体催化羟醛反应合成4-羟基-2-丁酮的空间位阻效应及动力学研究

摘要 4-羟基-2-丁酮作为医药和食品工业领域的重要化工中间体，传统上由甲醛和丙酮通过羟醛反应合成，由于存在重副反应，选择性较低。在此，为该反应过程制备了一系列具有不同空间位阻阳离子的碱性离子液体。催化性能评价结果表明，4-羟基-2-丁酮的选择性可以随着离子液体阳离子中取代烷基链长的延长和取代烷基数量的增加而提高。并且四辛基氢氧化铵（[N8,8,8,8]OH）被确定为最佳离子液体催化剂，在40°C下对4-羟基-2-丁酮的选择性为91.1%。