Quantum-chemical study of organic reaction mechanisms. Part 2. Addition of selenium dichloride to acetylene

•The mechanism of the addition of selenium dichloride to acetylene has been theoretically studied.•The reaction proceeds via a selenirenium intermediate with the four-coordinated selenium atom.•The intermediate exhibits a trigonal-bipyramidal configuration.•The obtained results are in good agreement with the experimental data.

The mechanism of the addition of selenium dichloride to acetylene has been studied theoretically at the DFT-B3LYP/6-311+G(d,p) level. The reaction proceeds as anti-anti-addition via the formation of the intermediate selenirenium compounds with the four-coordinated selenium atom. Both thermodynamically and kinetically, a favorable E-2-chloroselenenyl chloride is formed on the first stage of the reaction. The experimentally observed E,E-bis(2-chlorovinyl) selenide is kinetically more favorable as compared to E,Z-isomer. Possible alternative reaction mechanisms require much higher energy barriers. Stereoselectivity of the process is achieved through the kinetic control of the reaction. In the reaction profile of a preferable route leading to a kinetically favorable E,E-bis(2-chlorovinyl) selenide the entropy factor doesn't play a major role in the energetics of both stages.

Graphical abstractThe reaction of selenium dichloride with acetylene proceeds as anti-anti-addition via the formation of intermediate selenirenium compounds with the four-coordinated selenium atom.Figure optionsDownload full-size imageDownload as PowerPoint slide