molecules with torsional tops is described in detail for the example of benzoic series molecules. A complex of
original programs was used to identify torsional transitions and fundamental frequency progressions, to con-
struct and process several Deslandres tables for torsional transitions, to optimize the geometry of molecules,
and to determine the dependence of the reduced moment of inertia on angle
taking into account geometric structure relaxation. Internal rotation potential function parameters were calculated for benzaldehyde, benzoyl
fluoride, and benzoyl chloride. The calculated parameters were in close agreement with the results of quantum-
mechanical calculations.