CONFORMATIONAL EQUILIBRIA OF 5-SUBSTITUTED 1,3-DIOXANES - STUDY OF SOLVENT EFFECTS

Conformational equilibria of 5-substituted, 1,3-dioxanes have been stu died by means of the PM3 method. The role of the solvent is analyzed b y using a self-consistent reaction field model. Complete geometry opti mizations have been carried out for the isolated and solvated species. A noticeable solvent effect on the equilibrium geometry has been foun d for the methoxy derivative. The modification of the axial-equatorial equilibrium under the solvent effect is discussed and the theoretical energy variations are compared to available experimental data. Specif ic solute-solvent interactions seem to be implied in some particular c ases in which the observed solvent effect goes in the opposite directi on to that expected on the basis of pure electrostatic interactions. T his point is analyzed by comparing the results obtained in cavity and supermolecule model computations.