Potential functions of N–C and C–S internal rotations and normal coordinate analyses of carbamothioic acid H2N–CO–SCl

摘要

The structural stability of carbamothioic acid NH2CO–SCl was investigated by DFT-B3LYP and ab initio MP2 calculations using 6-311+G** basis set. Full energy optimizations were carried out and the molecule was predicted to exist predominantly in the trans (CO and S–Cl bonds are anti to each other) conformation. From the calculations, the two-fold NH2 barrier about the N–C bond was calculated to be about 12 kcal/mol, while, the asymmetric OCSCl barrier about the C–S bond to be about 8 kcal/mol. The vibrational frequencies of the d0- (NH2COSCl) and d2- (ND2COSCl) deuterated species of the molecule were computed at the DFT-B3LYP level. Then vibrational assignments for the normal modes of the compound in its stable trans conformation were made on the basis of normal coordinate calculations.