Infrared Spectra of Partially Deuterated Acetamide

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Abstract
The infrared spectra of orthorhombic crystals of CH3CONH2, CD3CONH2, and their N-deuterated and partially N-deuterated samples have been recorded in the region between 4000 and 400 cm−1. The bands due to the trans- and cis-NHD species have been assigned by comparing the spectra of various samples containing the NH2, ND2 and NHD species in different proportions. In the spectra of the 50% N-deuterated samples, the absorption bands near 1530 and 1360 cm−1have been assigned to the amide II and III modes, respectively, of the trans-NHD species characteristic of the trans conformation of the -CONH- group, and those near 1480 and 1400 cm−1to the NH in-plane deformation and the CN stretching modes, respectively, of the cis-NHD species. These assignments were confirmed by the normal coordinates analysis of eight isotopic species of acetamide based on the Urey-Bradley force field.