The molecular structures of divinyl sulfide and divinyl sulfoxide in the gas phase from electron diffraction

Abstract

The molecular geometries and conformations of divinyl sulfide (DVS). (CH₂CH)₂S, and divinyl sulfoxide (DVSO), (CH₂CH)₂SO, have been determined by gas-phase electron diffraction and vibrational analysis. The CC bonds tend to eclipse other bonds or a sulfur lone pair in the free molecules. The only conformer found in the vapours of DVS at room temperature has no symmetry and is characterized by dihedral angles C–S–CC of 32(9)° and –148(7)°; both CH₂ groups lie on the same side of the C–S–C plane. This form is very similar to the prevailing form of divinyl ether.⁸ DVSO is a mixture of conformers. The form present in 78(17)% at 82 °C has C–S–CC of 121(4)° and –121(4)° and C_ssymmetry; both CC bonds eclipse the SO bonds. Intramolecular O ⋯ H(C) interactions of about 2.5 Å seem to stabilize existing conformers of DVSO. Important parameters are (r_g with estimated total errors), for DVS: S–C 1.758(4), CC 1.342(3), C–H 1.092(3). (C·H)_mean(within a CH₂CH group) 2.108(6)Å, C–S–C 101.8(21)°, S–CC 123.7(6)°; for DVSO: SO 1.477(3), S–C 1.785(4). CC 1.330(3), C–H 1.091(5), (C·H)_mean 2.141(10)Å, C–SO 107.5(14)°, C–S–C 99.2(18)°, S–CC 118.5(8)°. Bond lengths do not indicate effects of conjugation in these molecules.