Affiliation: | Biology Department, University of Pennsylvania, Philadelphia, Pennsylvania 19147 U.S.A. Chemistry Department, Philadelphia College of Textiles & Science, Philadelphia, Pennsylvania 19144 U.S.A. Physics Department, The Pennsylvania State University, Ogontz Campus, Abington, Pennsylvania 19001 U.S.A. |
Abstract: | The energy and force field for the planar cis and trans conformers of thionformic acid have been calculated using the 4–31 G basis set, augmented by a complete set of d-functions on the sulfur atom, with full geometry optimization. Extensive comparisons are made between the changes in geometry and selected force constants in going from cis- (chain) to the trans- (ring) structures of thionformic, thiolformic and formic acid. These changes are discussed in terms of a hydrogen bonding type of interaction in the O---HS, S---HO and O---HO structural units respectively. Of the thioacid conformers, the trans-thiol is found to be the most stable; the trans-thion and cis-thiol both about 10 kJ mol−1 less stable; and the cis-thion the least stable by about 38 kJ mol−1. |