Citation: Wang Yan, Fang De-Cai, Fu Xiao-Yuan. Theoretical Studies on the Mechanism of Dimerization Reactions of Thioketene[J]. Acta Physico-Chimica Sinica, 1999, 15(01): 35-39. doi: 10.3866/PKU.WHXB19990107
硫代双烯酮二聚反应机理的理论研究
利用HF／6－31G*及半经验分子轨道AM1法，研究了硫代双烯酮及双三氟甲基硫代双烯酮二聚反应的反应机理，采用Berny梯度法优化得到反应的过渡态，并进行了振动分析确认，计算结果表明：（1）所有的二聚反应均是按照非同步的协同途径，经过扭曲的四元环过渡态进行的；（2）硫代双烯酮的二聚反应，三种可能的二聚方式中，生成对称四元杂环产物的二聚反应的活化焓最高；（3）双三氟甲基硫代双烯酮的二聚反应，生成对称四元杂环产物的二聚方式其活化焓比另外两种二聚方式的活化焓要低得多，这与实验中只观察到生成对称四元杂环产物的结果是一致的.
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关键词:
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硫代双烯酮
- / 双三氯甲基硫代双烯酮
- / 二聚
- / 反应机理
English
Theoretical Studies on the Mechanism of Dimerization Reactions of Thioketene
Dimerization reactions of thioketene and bis(trifluoromethyl) thioketene have been studied by means of HF/6-31G* and semiempirical AMI. All the geometries of the stationary points on the reactions path have been optimized by energy gradient technique, and all the transition states were characterized by vibration frequency analysis. The results can be summed up as follows: three different dimerization processes of thioketene and bis(trifluoromethyl)thioketene are all concerted but nonsynchronous,taking place through twisted four-membered cyclic transition states. The activation enthalpies were calculated to be 122.53, 126.47 and 136.68 kJ•mol-1 respectively for three thioketene dimerization processes. Contrarily, for the three bis(trifluoromethyl)thioketene dimerization reactions, the activation enthalpies are 287.05,274.65 and 218.84kJ•mol-1 respectively, which are in consistence with experimental fact.
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Key words:
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Thioketene
- / Bis(trifluoromethy)thioketene
- / Dimerization
- / Reaction mechanism
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