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首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Effect of Substituents on the Stability of Sulfur-Centered Radicals
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Effect of Substituents on the Stability of Sulfur-Centered Radicals

机译：取代基对以硫为中心的自由基的稳定性的影响

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摘要

High-level ab initio calculations have been used to calculate the standard and inherent radical stabilities (RSEs) of a test set of 41 sulfur-centered radicals, chosen for their relevance in fields as diverse as combustion, atmospheric chemistry, polymer chemistry, and biochemistry. Radical stability was shown to be profoundly affected by substituents, varying over a 30 kcal mol(-1) range for the test set studied. Like carbon-centered radicals, substituent effects on sulfur-centered radical stabilities result from the competition between the stabilizing effect of electron delocalization by lone pair donation and g-acceptance, and the destabilizing effect of 6 withdrawal. However, in contrast to carbon-centered radicals, the heavier thiyl radicals are better able to undergo resonance and lone-pair donor interactions with heavier substituents. In particular, sulfur-containing lone pair donor and pi-acceptor substituents have the greatest stabilizing effect, whereas sigma-withdrawing substituents such as carbonyls and pyridines are the least stabilizing. The stabilities predicted using the, standard definition and Zavitsas's inherent RSEz scheme are shown to be in surprisingly good agreement with one another for most species tested. The RSEz values have also been shown to be capable of making chemically accurate estimates of bond energies by comparing our calculated values with 34 currently available experimental ones.
机译：已使用高级从头算计算来计算测试集中的41个以硫为中心的自由基的标准和固有自由基稳定性（RSE），并选择了它们在燃烧，大气化学，聚合物化学和生物化学等领域的相关性。自由基稳定性受取代基的影响很大，所研究的测试套件在30 kcal mol（-1）范围内变化。像以碳为中心的自由基一样，取代基对以硫为中心的自由基稳定性的影响是由孤对捐赠和g接受对电子离域的稳定作用与6撤离的不稳定作用之间的竞争所致。然而，与以碳为中心的基团相反，较重的噻吩基团更能与较重的取代基发生共振和孤对供体相互作用。特别地，含硫的孤对供体和π-受体取代基具有最大的稳定化作用，而吸取σ的取代基如羰基和吡啶则具有最小的稳定化作用。对于大多数测试物种，使用标准定义和Zavitsas固有的RSEz方案预测的稳定性显示出令人惊讶的良好一致性。通过将我们的计算值与34个当前可用的实验值进行比较，还显示出RSEz值能够对键能进行化学上准确的估算。

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