AB-INITIO C-13 NUCLEAR SHIELDING CALCULATIONS FOR SOME SOLID AMINO-ACIDS USING THE GIAO PROCEDURE

The results of ab initio GIAO-CHF C-13 nuclear shielding calculations for some solid amino acids, performed with the 6-311G** and a locally dense basis set are reported. Comparison of the present calculation with the observed shieldings shows an RMS error of 6.6 ppm. Shieldings of the carbon nuclei which are multiply bonded are strongly influenced by electron correlation effects, Experimental molecular geometries used in these calculations were taken from crystal structures of amino acids.