ABINITIO MOLECULAR-ORBITAL STUDY OF DEPROTONATION OF AMINES

The geometries of the amines NH2X and amido anions NHX−, where X = H, CH3, NH2, OH, F, C2H, CHO, and CN have been optimized using ab initio molecular orbital calculations with a 4‐31G basis set. The profiles to rotation about the NX bonds in CH3NH−, NH2NH−, and HONH− are very similar to those for the isoprotic and isoelectronic neutral compounds CH3OH, NH2OH, and HOOH. The amines with unsaturated bonds adjacent to the nitrogen atoms undergo considerable skeletal rearrangement on deprotonation such that most of the negative charge of the anion is on the substituent. The computed order of acidity for the amines NH2X is X = CN > HCO > F ≈ C2H > OH > NH2 > CH3 > H and for the reaction NHX− + H+ → NH2X the computed energies vary over the range 373–438 kcal/mol. Copyright © 1978 John Wiley & Sons, Inc.