中文摘要：

以醋酸铀酰为主要试剂，在负离子检测模式下，采用电喷雾串联质谱法制备了甲基羟基铀酰负离子．实验发现，气相中的甲基羟基铀酰离子与水分子发生分子离子复分解反应，并用串联质谱法对反应产生的离子性产物进行了结构确认，提出了反应的可能机理．热力学计算结果表明，该反应的△Greaction为-473．0kJ/mol，△HReaction为-236．5kJ／mol，△SSystem为0．792kJ·mol^-1·K^-1．该反应的速率常数为2．26s^-1．

英文摘要：

Negatively charged organic uranyl species（ CH3UO2OH） was prepared and characterized with electrospray ionization tandem mass spectrometry implemented on an LTQ-MS instrument. Experimentally, it was found that ionic species of CH3UO2OH underwent metathetical reaction with water molecules present in the ion trap to produce negative ions of m/z 304 and a neutral methane species in the gas phase. The transient state of the reaction was observed and identified in the gas phase by tandem mass spectrometry. The mechanism was discussed in detail. The Gibbs free energy（△rG）, enthalpy（△rH） and entropy（△rS） for the reaction were calculated, on the basis of the experimental measurements, to be -473.0 kJ/mol, -236. 5 kJ/mol and 0. 792 kJ·mol^-1·K^-1 , respectively. The reaction rate constant was experimentally estimated to be 2. 26 s^-1.