S-nitrosocysteine and the isotopically-substituted S<sup>15</sup>NO- and N-<i>d</i><sub>3</sub> analogs have been prepared. FT-IR spectra have been obtained on the normal molecule and the <sup>15</sup>N isotopomer. Spectra of the N-<i>d</i><sub>3</sub> analog were obtained with a dispersive instrument. The fundamental frequencies of the three isotopomers were calculated by using force constants previously obtained through overlay calculations on amino acids and from a normal coordinate analysis of methyl thionitrite. The average computational error between the observed and calculated frequencies using the transferred force constants was 11 cm<sup>−1</sup>. This difference was decreased to 7 cm<sup>−1</sup> by slightly modifying some of the force constant values by a least-squares refinement. Vibrational assignments are made for all three isotopic analogs by utilizing the potential energy distribution. Out of a total of 96 fundamentals occurring above 300 cm<sup>−1</sup>, 65 may be classified as group vibrations by the potential energy criterion.
D. Michael Byler, Heino Susi, and Walter V. Gerasimowicz, "Vibrational Spectra, Assignments, and Valence Force Field for S-nitrosocysteine and Isotopic Analogs," Appl. Spectrosc. 38, 200-203 (1984)