A VIBRATIONAL MOLECULAR-FORCE FIELD OF MODEL COMPOUNDS WITH BIOLOGICAL INTEREST .5. HARMONIC DYNAMIC OF N-ACETYL-ALPHA-D-GLUCOSAMINE IN THE CRYSTALLINE STATE

Combining the modified Urey-Bradley-Shimanouchi intramolecular potential energy function with an appropriate intermolecular energy function, normal coordinate calculations have been performed for N-acetyl-alpha-D-glucosamine in the crystalline state. The infrared spectra in the mid range (4000-500 cm-1) and the Raman spectra in 3500-20 cm-1 range were recorded. The overall agreement between the observed and calculated frequencies led to an average error of the order of 3.5 cm-1. The computed potential energy distribution was found to be compatible with previous assignments Of D-glucose and D-galactose for the pyranose ring and for N-methylacetamide for the acetamido group. The set of force constants used for N-acetyl-alpha-D-glucosamine was approximately the same as that obtained for the glucose and N-methylacetamide respectively for the pyranose ring and the acetamido group, a difference existing only for the atoms involved in the anomeric and hydroxy groups.