EXPERIMENTAL AND THEORETICAL-STUDIES OF ISOMERIC C2H5S AND C2H5S+

By combining photoionization and photodissociation measurements with ab initio Gaussian-2 (G2) calculations on the C2H5S and C2H5S+ system, we have concluded that CH3CH2S is the dominant primary product formed in the 193 nm photodissociation of (CH3CH2)2S, while CH3CHSH+ is the product ion formed at the photoionization onset of C2H5S+ from (CH3CH2)2S. The G2 predictions for the heats of formation at 0 K (DELTAH(f0)) for the isomers of C2H5S and C2H5S+ (CH3CH2S: DELTAH(f0)(G2) = 27.5 kcal/mol; CH3SCH2: DELTA(Hf0)(G2) = 37.3 kcal/mol; CH3CH2S+: DELTAH(f0)(G2) = 236.5 kcal/mol; CH3CHSH+: DELTAH(f0)(G2) = 192.6 kcal/mol; and CH3SCH2+: DELTAH(f0)(G2) = 195.3 kcal/mol) are in agreement with available experimental DELTAH(f0) values (CH3CH2S: DELTAH(f0)(exp) = 31.4+/-2 kcal/mol; CH3SCH2: DELTAH(f0)/(exp) = 34.8+/-2.5 kcal/mol; CH3CH2S+: DELTAH(f0)(exp) = 238.3+/-2 kcal/mol; CH3CHSH+: DELTAH(f0)(exp) = 189.6+/-1.0 kcal/mol; and CH3SCH2+: DELTAH(f0)(exp) = 195.1 kcal/mol). The G2 calculation also yields a value of 35.3 kcal/mol for DELTAH(f0)(CH3CHSH).