Abstract: The geometries of cyclopropanethione (la), methylenethiuane (2a), cyclopropanethione S-oxide (lb), methylenethiirane S-oxide (Zb), cyclopropanethione S, S- dioxide (IC), methylenethiirane S, S-dioxide (2c), thioformaldehyde S $-dioxide (sulfene), and the tetramethyl derivatives of lb and 2b, tetramethylcyclopropanethione S-oxide (Id) and 3, 3-dimethyl-2-isopropylidenethiirane S-oxide (td), respectively, were optimized at the ...