Raman Spectra of Gaseous CH3ND2, C2H5ND2, and n-C3H7ND2. The Raman and Infrared Spectra of Gaseous CH3NHD

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Abstract
The Raman spectra of gaseous CH3ND2, C2H5ND2, and n-C3H7ND2, as well as the Raman and the infrared spectra of gaseous CH3NHD, have been measured and analyzed with respect to the amino group vibrations. The asymmetric position of the ND stretching vibration of CH3NHD relative to the ND2 stretching vibrations of CH3ND2 is explained by Fermi resonance of the symmetric ND2 stretching vibration with the overtone of the ND2 deformational vibration. A band of CH3NHD found at 878 cm−1 in the infrared spectrum only shows a splitting analogous to that of the band at 688 cm−1 which has been analyzed by Tsuboi et al. in the infrared spectrum and which now also has been found in the Raman spectrum. It is assigned to the higher frequency NHD out of plane bending vibration, formally denoted as NHD twisting vibration, whereas the band at 688 cm−1 belongs to the lower frequency NHD out of plane bending vibration, formally the NHD wagging vibration. Using the sum rule, the twisting vibrations of CH3NH2 and CH3ND2, until now not unequivocally observed, are calculated as approximately 980 and 820 cm−1. The observations for C2H5NH2 and C2H5ND2 and the results of normal coordinate treatments performed by Wu, Zerbi, Califano, and Crawford as well as by Dellepiane and Zerbi are in agreement with such an assignment.