Theoretical study on the unimolecular decomposition of thiophenol

The potential energy surface for the unimolecular decomposition of thiophenol (C6H5SH) is mapped out at two theoretical levels; BB1K/GTlarge and QCISD(T)/6‐311+G(2d,p)//MP2/6‐31G(d,p). Calculated reaction rate constants at the high pressure limit indicate that the major initial channel is the formation of C6H6S at all temperatures. Above 1000 K, the contribution from direct fission of the SH bond becomes important. Other decomposition channels, including expulsion of H2 and H2S are of negligible importance. The formation of C6H6S is predicted to be strong‐pressure dependent above 900 K. Further decomposition of C6H6S produces CS and C5H6. Overall, despite the significant difference in bond dissociation, i.e., 8‐9 kcal/mol between the SH bond in thiophenol and the OH bond in phenol, H migration at the ortho position in the two molecules represents the most accessible initial channel. © 2011 Wiley Periodicals, Inc. J Comput Chem, 2011