AB-INITIO CALCULATIONS OF THE NMR SHIELDING CONSTANTS FOR PROPIONITRILE DIMERS

The structures of three propionitrile dimers were optimized at the SCF level. Then the gauge-independent atomic orbitals coupled Hartree-Fock (GIAO-CHF) calculations of NMR shielding constants were performed for the isolated molecule and its optimized dimers. It was found that the association effects were significantly positive for the nitrogen shielding constants and negative for the cyano carbons. The shielding constants of the rest of the carbon and hydrogen atoms were only slightly affected by dimerization. The calculated association effects are consistent with the experimental results which are avialable from the NMR chemical shift measurements in liquid solutions.