Carbenes of the form HCXH (X=O, S, Se) exist in both cis and trans isomer forms in the ground singlet state, as well as in a skewed configuration in the lowest triplet state. Hydroxycarbene, HCOH, has received a great deal of recent experimental and computational scrutiny as an isomer of formaldehyde, H2CO, and is thought to play a role in H2CO photochemistry and in the reaction of C atom with H2O. Thiohydroxycarbene, HCSH, has been previously suggested as a possible product formed in the atmosphere of Jupiter as a result of the collision of Comet Shoemaker-Levy 9 with the planet in 1994. HCSH is also involved as an intermediate in the reaction of C atom with H2S. To the best of our knowledge, there have been no experimental or computational studies of the structure or properties of the selenium-containing analog, HCSeH. In this work, computational studies at the CCSD(T)/cc-pVTZ level and higher have been performed in order to elucidate key features of the potential energy surfaces of HCXH. In particular, the barrier for conversion from cis- to trans-1HCXH has been computed for each of the analogs, and results have been compared with previous computational results where available. The results indicate that the barriers to rotation are rather high for what would nominally be considered rotation about a C-X single bond, ranging from 26-38 kcal/mol depending upon the level of theory. The origin of the barriers to rotation for conversion between the cis and trans forms of HCXH has been explored in detail using a variety of techniques.

High level quantum mechanical studies of singlet carbenes HCXH (X=O, S, Se)

244th National Meeting (2012)

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