Potential energy surfaces for a series of intermolecular CH⋯O hydrogen bonds have been calculated in order to determine the Quantum Mechanical Reaction Coordinates (QMRCs). The results have shown that one QMRC curve is common for strong C–H⋯O hydrogen bonds, and another for very weak interactions. For intermediate hydrogen bonds the shape of the potential energy curve depends on the particular type of the C–H⋯O bond, which is related to the
