一个计算研究的thiobenzophenone S-甲基化物到thiobenzophenone的循环添加
Reiner Sustmann1, Willi Sicking, Rolf Huisgen
1Institut für Organische Chemie der Universität Duisburg-Essen, 45117 Essen, Germany. reiner.sustmann@uni-essen.de
Journal of the American Chemical Society
|November 20, 2003
概括
计算研究显示,硫二烯S-甲基化物对硫二烯的循环添加主要通过四基替代的C,C-双基中间体进行,导致4,4,5,5-四基-1,3-二硫的形成.
科学领域:
- 计算化学计算化学
- 有机反应机制 有机反应机制
背景情况:
- 硫二 S-甲基化物对硫二的循环添加是一种经过实验确定的反应.
- 了解精确的反应途径和中间物种对于机理学阐明至关重要.
研究的目的:
- 通过计算来研究硫二芬S-甲基化物循环添加到硫二的反应机制.
- 为了比较协同的路径,通过C,C-双根和C,S-zwitterions进行逐步反应.
- 评估不同计算方法对激进稳定能量的准确性.
主要方法:
- 使用无限制的Hartree-Fock (UHF) 与3-21G*基础设置用于静止点识别.
- 雇员不受限制的贝克,3-参数,李--帕尔 (U) B3LYP/6-31G*//(U) HF/3-21G*用于单点能量计算.
- 进行了额外的 (U) B3LYP/6-31G*优化来验证计算可靠性.
- 使用完整基准集 (CBS-QB3) 用于对债券解离能量的模型计算.
主要成果:
- 形成一个四基替代的C,C-二基中间体,然后环闭到4,4,5,5-四基-1,3-二甲基是最有利的能量途径.
- 区域异构体的2,2,4,4-四替代产品在热力学上比较稳定,17kcalmol(-1).
- (U) B3LYP计算倾向于高估基稳定能,而CBS-QB3则提供更接近实验值的结果.
- 硫烯S-甲基化物可以通过C,C-双基中间体二元化为2,2,3,3-四-1,4-二甲.
结论:
- 对于循环添加反应,C,C-二基通路在动力学上是首选的,尽管区域异构体产品的热力学稳定性更高.
- 像 (U) B3 LYP 这样的计算方法在评估涉及二基中间体的反应机制时可能需要仔细考虑,因为可能会高估基稳定性.
- 在这种系统中,CBS-QB3为计算债券解离能提供了更可靠的方法.
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