Non-bonded O⋯S contacts and O–H⋯S hydrogen bonds in isomeric hydroxyphenyl-1,3-dithianes

Abstract

Three isomeric hydroxyphenyl-1,3-dithianes, ortho-, meta- and para-HO–C₆H₄–C₄H₇S₂, have been synthesized and their crystal structures determined. The para isomer exhibits O–H⋯O hydrogen bonds between hydroxyl groups. The ortho- and meta isomers exhibit O–H⋯S hydrogen bonds. In the meta isomer, the hydroxyl group is disordered over two orientations, both of which give rise to comparable O–H⋯S hydrogen bonds. The meta isomer also includes non-bonded O⋯S contacts in which the O atoms approach S along the directions of the σ* orbitals of the S–C bonds in the dithiane ring. The observation in the ortho- and meta isomers of O–H⋯S hydrogen bonds in preference to O–H⋯O reflects the fact that efficient overall packing of the molecules brings the OH groups into the proximity of S atoms. Efficient packing is consistent with the formation of O–H⋯O hydrogen bonds only in the para isomer. The structures demonstrate that hydroxyl groups can perform a dual role in crystal structures in the presence of dithiane rings, forming O–H⋯S hydrogen bonds and also non-bonded O⋯S contacts in which O acts as a nucleophile.