In situ variable-temperature 1H,19F and 31P NMR spectroscopy was employed to study the thermal decomposition mechanisms of ionic liquid. At a temperature as low as 80℃, ionic liquid [C4mim][PF6], composed of 1-butyl-3-methylimidazolium cation (C4mim+) and hexafluorophosphate anion (PF6—), had a slow, but detectable decomposition. For dehydrated [C4mim][PF6], the ionic liquid started to decompose at temperature higher than 80℃. Small amount of PF5 and HF formed first. The proton in HF came from the proton at 2-position of 1-butyl-3-methylimidazolium cation ring. After losing the proton, a carbene structure was formed, which then formed complex with PF5. Free PF5 and PF5/carbene complex reached equilibrium at a ratio of 7:3.%利用原位变温核磁共振氢谱(1H NMR)、核磁共振氟谱(19F NMR)和核磁共振磷谱(31P NMR)等NMR技术研究特定温度下离子液体的热分解机理.在温度低至80℃时,1-丁基-3-甲基咪唑阳离子(C4mim+)和六氟磷酸根阴离子(PF6—)组成的离子液体[C4mim][PF6]呈现1个缓慢但明显的分解过程.无水[C4mim][PF6]在温度高于80℃时开始分解,生成少量的五氟化磷(PF5)和氟化氢(HF),氟化氢中的氢原子来自于1-丁基-3-甲基咪唑环2位上的氢原子.在丢掉这个氢原子后,阳离子成环形成一个卡宾,并与PF5形成卡宾/PF5复合物.定量NMR分析显示在分解反应达到平衡状态时,自由态PF5和卡宾/PF5复合物的比例为7:3.
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