College of Chemistry and Chemical Engineering, Chongqing University, Chongqing 400044, China.
J Mol Model. 2010 Dec;16(12):1931-7. doi: 10.1007/s00894-010-0688-6. Epub 2010 Mar 20.
Reactions of lithium halide (LiX, X = F, Cl, Br and I) and methyl halide (CH₃X, X = F, Cl, Br and I) have been investigated at the B3LYP/6-31G(d) level of theory using the microhydration model. Beginning with hydrated lithium ion, four or two water molecules have been conveniently introduced to these aqueous-phase halogen-exchange S(N)2 reactions. These water molecules coordinated with the center metal lithium ion, and also interacted with entering and leaving halogen anion via hydrogen bond in complexes and transition state, which to some extent compensated hydration of halogen anion. At 298 K the reaction profiles all involve central barriers ΔE ( cent ) which are found to decrease in the order F > Cl > Br > I. The same trend is also found for the overall barriers (ΔE(ovr)) of the title reaction. In the S(N)2 reaction of sodium iodide and methyl iodide, the activation energy agrees well with the aqueous conductometric investigation.
已在 B3LYP/6-31G(d)理论水平下使用微水合模型研究了卤化锂（LiX，X=F、Cl、Br 和 I）和卤代甲烷（CH3X，X=F、Cl、Br 和 I）的反应。从水合锂离子开始，已将四个或两个水分子方便地引入这些水相卤素交换 S(N)2 反应中。这些水分子与中心金属锂离子配位，并通过氢键与进入和离开的卤素阴离子相互作用，在一定程度上补偿了卤素阴离子的水合作用。在 298 K 下，反应轮廓都涉及中心势垒ΔE（cent），发现其顺序为 F>Cl>Br>I。标题反应的整体势垒（ΔE(ovr)）也呈现出相同的趋势。在碘化钠和碘甲烷的 S(N)2 反应中，活化能与水导电测量研究吻合较好。
