Intermolecular interaction and thermodynamic properties of N‐methylacetamide and hydroxyacetonitrile dimers

Abstract

AbstractAb initio Hartree–Fock (HF) and second‐order Møller–Plesset correlation energy correction (MP2) theories with 6–311+G* and aug‐cc‐pVDZ basis sets in combination with a counterpoise procedure for basis set superposition error (BSSE) correction were applied to the investigation of intermolecular interactions and thermodynamic properties of N‐methylacetamide and hydroxyacetonitrile (HAN) dimers. The heterodimer of N‐methylacetamide with HAN was selected as the computational model for the complex of cyclo[(S)‐His‐(S)‐Phe] (CHP) with (R)‐mandelonitrile, a chiral catalyst for the asymmetric hydrocyanation of aldehydes. Cyclic structures were identified as the most stable conformation in N‐methylacetamide dimer (I), HAN dimer (II) and their heterodimer (III). The corrected binding energies for I, II and III are −52.89, −45.83 and −49.95 kJ mol−1 at the MP2/aug‐cc‐pVDZ//HF/aug‐cc‐pVDZ level, respectively. The Gibbs free energy change (ΔG) in the process I+II → 2III was predicted to be −6.41 kJ mol−1 at 298.15 K. Dimer III can be spontaneously produced in the mixture of N‐methylacetamide and HAN, which is in agreement with the experimental fact that most cyanohydrins are capable of interacting with CHP and form non‐covalent complexes. Copyright © 2004 John Wiley & Sons, Ltd.