An Ab Initio Investigation of Molecules With a Disulfide Bond: (Hs)2, (Ch3s)2 and Cystine

ab initio Calculations at the Gaussian-70 STO-3G and 4-31G basis levels have been carried out for (HS)2 and (CH3S)2. Cystine was investigated at the STO-3G level. The STO-3G energy minimized geometry agrees well with experiments for (HS)2 and (CH3S)2. The barriers to internal rotation are predicted to be (at the 4.31G level): (HS)2, cis 8.5 kcal, trans 3.03 kcal; (CH3S)2, cis 18.47 kcal, trans 6.04 kcal.