Seckute Jolita, Menke Jessica L, Emnett Ryan J, Patterson Eric V, Cramer Christopher J
Truman State University, Division of Science, Kirksville, Missouri 63501-4221, USA.
J Org Chem. 2005 Oct 28;70(22):8649-60. doi: 10.1021/jo0502706.
[reaction: see text] Potential energy surfaces for the alkaline hydrolysis of sarin and O,S-dimethyl methylphosphonothiolate, a VX model compound, and the perhydrolysis of the latter have been computed at the MP2/6-31+G(d)//mPW1K/MIDI! level of theory. The effect of aqueous solvation was accounted for via the integral equation formalism polarizable continuum model (IEF-PCM) at the HF/6-31+G(d) level. Excellent agreement with the experimental enthalpy of activation for alkaline hydrolysis of sarin was found. For the alkaline hydrolysis of O,S-dimethyl methylphosphonothiolate, it was found that the P-O and P-S bond cleavage processes are kinetically competitive but that the products of P-S bond cleavage are thermodynamically favored. For the perhydrolysis of O,S-dimethyl methylphosphonothiolate, it was found that P-O bond cleavage is not kinetically competitive with P-S bond cleavage. In both cases, the data support initial formation of trigonal bipyramidal intermediates and demonstrate kinetic selectivity for nucleophilic attack on the face opposite the more apicophilic methoxide ligand.
[反应：见正文] 沙林和VX模型化合物O,S-二甲基甲基硫代磷酸酯碱性水解以及后者全水解的势能面已在MP2/6-31+G(d)//mPW1K/MIDI!理论水平上进行了计算。通过HF/6-31+G(d)水平的积分方程形式极化连续介质模型（IEF-PCM）考虑了水溶剂化的影响。发现与沙林碱性水解的实验活化焓有很好的一致性。对于O,S-二甲基甲基硫代磷酸酯的碱性水解，发现P-O和P-S键断裂过程在动力学上具有竞争性，但P-S键断裂的产物在热力学上更有利。对于O,S-二甲基甲基硫代磷酸酯的全水解，发现P-O键断裂在动力学上与P-S键断裂不具有竞争性。在这两种情况下，数据都支持三角双锥中间体的初始形成，并证明了亲核攻击在与亲核性更强的甲氧基配体相对的面上的动力学选择性。
