Configurational characteristics of the polysulfides, . Dipole moments and gauche effects in poly (1,3‐dithiocane)

Abstract

AbstractSeveral earlier studies of poly(alkylene sulfides) have not yielded evidence for a sulfur gauche effect, in contrast to the large attractive gauche effect found particularly in the lower members of the poly(alkylene oxides). In this study the dipole moments at 25°C and the corresponding temperature coefficient of poly(1,3‐dithiocane)Structure based name: poly(thiomethylonethiopentamethylene). [SCH2S(CH2)5]x are calculated in the rotational isomeric‐state approximation, and the results compared to the values determined by experiment. In the calculations the energy Eσ′ = [Eg± − Et] associated with S. . .CH2 interactions in the SCH2SCH2 segment is adjusted to attain agreement between theory and experiment. The results indicate that an extra stabilization energy of ca. 0,9 kcal . mol−1 must be added to these gauche states relative to the trans state (beyond that determined by conformational energy calculations based on semiempirical potential energy functions). This provides the first evidence of a large attractive sulfur gauche effect in the polysulfides, about equal in magnitude to that found for the analogous poly(methylene oxide).