THE NATURE OF THE N-H O=C HYDROGEN-BOND - AN INTERMOLECULAR PERTURBATION-THEORY STUDY OF THE FORMAMIDE FORMALDEHYDE COMPLEX

We have used Hayes‐Stone Intermolecular Perturbation Theory (IMPT) to study the variation with distance and orientation of the various components of the interaction energy of the N  H…O = C hydrogen bonded trans‐ formamide/formaldehyde complex, a model system for hydrogen bonding in proteins. The directionality of the total interaction energy is similar to that of the electrostatic component alone. We have analysed our data in terms of two model atom‐atom intermolecular potentials, using an isotropic functional form and an anisotropic one. The anisotropic form gives an excellent representation of the IMPT potential energy surface, considerably better than the isotropic model, and is comprised entirely of theoretically justified, physically meaningful terms. Copyright © 1990 John Wiley & Sons, Inc.