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

Ab 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 (Δ G ) in the process I + II → 2 III 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.