Analysis of the NMR Spectrum of Phenylethane-1,2-Dithiol

Abstract

The NMR spectrum of phenylethane-1,2-dithiol has been analyzed completely (except for the aromatic protons) by Reilly's new computer program MARIPI which is based on the Swalen and Reilly programs NMRIT and NMRENI. The geminal coupling constant, J34, was assumed to be negative in accord with the recent theoretical and experimental evidence on the signs of (H,H) coupling constants. The magnitudes of the two vicinal H-C-C-H coupling constants, J35 and J45, indicate that the molecule exists primarily in the two forms with gauche-trans arrangement of the hydrogen atoms on these carbon atoms The H-C-S-H coupling constants, J13, J14, and J25, can be either positive or negative in sign; however, a positive sign is favored in line with the –, +, – pattern of sign-alternation for (H,H) coupling across 2, 3, and 4 bonds. The long-range coupling constants, J15, J23, and J24, are small and probably negative. The very long-range coupling between the S-H protons, J12, is too small to be determined