The dimerization and trimerization of thioformaldehyde as well as the dimerization of thioketene has been studied using G3(MP2) calculations. The investigations have elucidated the reaction mechanisms. The activation Gibbs energy of the trimerization of thioformaldehyde has been determined as 118.1 kJ/mol and that of the dimerization of thioketene as 139.2 kJ/mol. The trimerization of thioformaldehyde is shown to proceed through an open chain dimer with the activation Gibbs energy 74.0 kJ/mol. The results explain that the direct dimerization of thioformaldehyde to 1,3-dithietane is not experimentally observed.
Journal of Molecular Structure: Theochem, 2010, Vol 944, Issue 1-3, p. 83-88