School of Chemistry, Sichuan University, Chengdu, China.
J Comput Chem. 2011 Sep;32(12):2545-54. doi: 10.1002/jcc.21834. Epub 2011 May 19.
The alkaline hydrolysis reaction of ethylene phosphate (EP) has been investigated using a supermolecule model, in which several explicit water molecules are included. The structures and single-point energies for all of the stationary points are calculated in the gas phase and in solution at the B3LYP/6-31++G(df,p) and MP2/6-311++G(df,2p) levels. The effect of water bulk solvent is introduced by the polarizable continuum model (PCM). Water attack and hydroxide attack pathways are taken into account for the alkaline hydrolysis of EP. An associative mechanism is observed for both of the two pathways with a kinetically insignificant intermediate. The water attack pathway involves a water molecule attacking and a proton transfer from the attacking water to the hydroxide in the first step, followed by an endocyclic bond cleavage to the leaving group. While in the first step of the hydroxide attack pathway the nucleophile is the hydroxide anion. The calculated barriers in aqueous solution for the water attack and hydroxide attack pathways are all about 22 kcal/mol. The excellent agreement between the calculated and observed values demonstrates that both of the two pathways are possible for the alkaline hydrolysis of EP.
采用超分子模型研究了磷酸乙烯酯（EP）的堿水解反应，其中包含几个显式水分子。在气相中和在 B3LYP/6-31++G(df,p) 和 MP2/6-311++G(df,2p) 水平下，计算了所有稳定点的结构和单点能。通过极化连续体模型（PCM）引入了水整体溶剂的影响。考虑了水进攻和氢氧根进攻途径，对 EP 的堿水解进行了研究。对于这两种途径，都观察到了一个协同机制，其中动力学上不重要的中间体。水进攻途径涉及在第一步中水分子的进攻和从进攻水中到氢氧根的质子转移，然后是一个内环键断裂到离去基团。而在氢氧根进攻途径的第一步中，亲核试剂是氢氧根阴离子。在水溶液中，水进攻和氢氧根进攻途径的计算壁垒都约为 22 kcal/mol。计算值与观察值之间的良好一致性表明，对于 EP 的堿水解，这两种途径都是可能的。
