Table 4.

Torsion barrier energies relative to the cis conformation in the gas phase ^a.

	CH3COOCH3	CH3COSCH3
B3LYP/6-311++G** b	13.35	11.80
B97D/aug-cc-pvtz c	12.40	12.16
MP2/6-311++G** b	13.45	11.18
MP2/aug-cc-pv(t+d)z		11.98
INDO d	29.10	14.06
PM3		6.05
PM6		6.53
PDDG/PM3		4.87

^a Energies in kcal/mol. ^b Ref. [7]. ^c Plus a set of “d” functions for the S-methyl thioacetate. ^d Rigid rotation, spd basis for S-methyl thioacetate, ref. [38].