Résumé
The three forms of glycine in the solid state, α, β, and γ are described and modeled by means of generalized-gradient approxn. (GGA) ab initio calcns. In particular, the location of the protons in each structure is studied. The vibrational frequencies and the NMR chem. shifts of 1H, 13C, and 15N in the three polymorphs are calcd. and compared to exptl. data (IR and Raman, solid-state magic angle spinning NMR, resp.). 13C chem. shift differences on the order of 1 ppm, which constitute the most accurate way to discriminate between the three structures when x-ray diffraction is not available, can be satisfactorily predicted. [on SciFinder(R)]