We develop a very general computational scheme allowing all the physical contributions to the solute-solvent interaction in the quantum chemical study of a solvated molecule to be taken into account. This scheme is based upon a model in which the solvent is assimilated to a continuum and the solute placed in a cavity of any shape. This approach takes advantage of the facilities offered by the reaction field factors formalism, which generalizes a model introduced by Kirkwood. Applied to the study of the liquid state structure of formamide and acetamide and to the solvent effects on the barrier to internal rotation in these molecules this method appears to be quite efficient. It offers a large number of possible applications to problems of chemical interest.