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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Ultrasonic chemical oxidative degradations of 1,3-dialkylimidazolium ionic liquids and their mechanistic elucidations
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Ultrasonic chemical oxidative degradations of 1,3-dialkylimidazolium ionic liquids and their mechanistic elucidations

机译：1,3-二烷基咪唑鎓离子液体的超声化学氧化降解及其机理研究

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摘要

A highly efficient process for oxidative degradation of 1,3-dialkylimidazolium ionic liquids in hydrogen peroxide/acetic acid aqueous medium assisted by ultrasonic chemical irradiation is, for the first time, described. It is shown that more than 93% of the 1,3-dialkylimidazolium cation with the corresponding Cl-, Br-, BF4- and PF6- counter-anions at a concentration of 2.5 mM can be degraded at 50 degrees C within 12 h while at 72 h the conversions approach 99%. A tentative mechanism for the degradation of these ILs is for the first time proposed through a detailed kinetic analysis of several characteristic transients and/or immediate products, which are identified during the ILs degradation using GC-MS. The results clearly indicate that three hydrogen atoms in the imidazolium ring are the first sites preferably oxidized, followed by cleavage of the alkyl groups attached to the N atoms from the ring. The nature of the alkyl chain length on the imidazolium ring and the type of counter anion do not seem to affect the degradation process. Further, selective fragmentations of C-N bonds of the imidazolium or derived ring lead to ring opening, forming degraded intermediates. It is also shown that acetoxyacetic acid and biurea are the final kinetically stable degraded products from the ILs under the degradation conditions.
机译：首次描述了在超声化学辐射的辅助下，在过氧化氢/乙酸水介质中氧化降解1,3-二烷基咪唑鎓离子液体的高效方法。结果表明，浓度为2.5 mM的1,3-二烷基咪唑鎓阳离子与相应的Cl-，Br-，BF4-和PF6-抗衡阴离子中，有93％以上可在50摄氏度下于12小时内降解。在72小时时，转化率接近99％。通过对几种特征瞬态和/或直接产物的详细动力学分析，首次提出了一种降解这些IL的尝试性机制，这些动力学瞬态和/或即时产物是使用GC-MS在IL降解过程中确定的。结果清楚地表明，咪唑鎓环中的三个氢原子是优选被氧化的第一个位点，随后从环上裂解连接至N原子的烷基。咪唑环上烷基链长度的性质和抗衡阴离子的类型似乎不影响降解过程。此外，咪唑或衍生的环的C-N键的选择性断裂导致开环，形成降解的中间体。还显示出乙酰氧基乙酸和双脲是在降解条件下来自IL的最终动力学稳定的降解产物。

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