期刊
CHEMICAL SCIENCE
卷 3, 期 6, 页码 1903-1918出版社
ROYAL SOC CHEMISTRY
DOI: 10.1039/c2sc20115a
关键词
-
资金
- Israeli Science Foundation (ISF) [09/53]
- special Minerva Grant
The paper addresses the surging topic of H-abstractions by closed-shell molecules, such as MnO4-, alpha-methylstyrene, ketones, metal-oxo reagents, etc. It is found that in the normal hydrogen atom transfer (HAT) regime, closed-shell abstractors require high barriers for H-abstraction. Under certain conditions a closed-shell abstractor can bypass this penalty via a proton-coupled electron transfer (PCET) mechanism. This occurs mainly in the identity reactions, e. g. MnO4- abstracting a hydrogen atom from MnO4H-center dot, but not in the corresponding non-identity reactions with alkanes. The usage of the valence bond (VB) diagram model allows us to characterize the HAT/PCET mechanistic relationship and bridge their reactivity patterns. It is thus shown that in the normal HAT regime, high barriers for closed-shell abstractors occur due to the additional promotion energy that is required in order to create a radical center and prepare the abstractor for H-abstraction. Mixing of the PCET states into the HAT states mitigates however these high barriers. The variable HAT/PCET mixing in a reaction series is discussed and its consequences for reactivity are outlined. It is shown that non-identity reactions sample PCET characters that depend, among other factors, on the C-H bond strength of the alkane, and hence may cause the Marcus analysis to produce different identity barriers for the same identity reaction.
作者
我是这篇论文的作者
点击您的名字以认领此论文并将其添加到您的个人资料中。
推荐
暂无数据