Conformations and temperature variation of the dipole moments of the alkoxy- and alkylthioethenes and their heteroorganic analogs

Abstract

1. The alkoxy- and alkylthioethenes with normal radicals and Me groups exist predominantly in the s-cis conformation; the fact that their dipole moments increase with rising temperature is due to an increase in the fraction of molecules in the energetically favored, more polar, gauche form. 2. The alkoxy- and alkylthioethenes with tertiary radicals exist in the single gauche conformation. The fact that the dipole moments of these compounds decrease with rising temperature is due to an increase of the population of the upper torsional vibrational levels for rotation relative to the\(C_{sp^2 } - X (X = O, S)\) bond with approach to the less polar s-trans structure. 3. The lack of a temperature variation in the dipole moments in the Me3ESCH = CH2 vinyl sulfides is due to the fact that the polarity is only weakly dependent on the angle of rotation in the E-S-C=C system.