Vibrational spectra and normal vibrations of acetanilide and N-deuterated acetanilide

The Raman and infra-red spectra of acetanilide and N-methylacetamide and of their N-deuterated compounds have been recorded. The vibrational frequencies of acetanilide have been assigned and the nature of the Amide I, II and III bands in acetanilide and N-methylacetamide has been investigated by the study of the changes in the frequencies of these bands in the spectra of their deuterated compounds. Acetanilide and deuterated acetanilide molecules have been subjected to normal co-ordinate treatment and the mixing up of the skeletal frequencies arising out of the in-plane vibrations has been determined. These results indicate that as in secondary amides, the amide II and amide III bands in acetanilide are due to the combined contribution ofδ (NH) andν (C-N) vibrations, but the contribution ofν (C-N) to the amide II band is less in acetanilide and deuterated acetanilide than in cases of N-methylacetamide and deuterated N-methylacetamide.     

Infrared and Raman spectra and normal vibrations of N,N-dimethylthioformamide and N,N-dimethylthioacetamide

The Raman and infrared spectra of N, N-dimethylthioformamide and N, N-dimethylthioacetamide were recorded and the vibrational frequencies are assigned. The normal co-ordinate treatment of these molecules has been carried out and the potential energy distributions calculated in order to clarify the nature of normal vibrations and investigate the magnitude of mixing up of various skeletal frequencies. The results in regard to the nature of the C-N and C=S stretching frequencies in these thioamides are compared with those of primary and secondary thioamides on the one hand and those of the corresponding ordinary tertiary amides on the other. It has been shown that the force constants of the general quadratic force field type are transferable in the series of molecules of tertiary amides and tertiary thioamides. The lowest frequency in the region of 150 cm.^?1 to 160 cm.^?1 has been recorded by the authors in the Raman spectra of the two tertiary thioamides under consideration. In the normal vibrational analysis of related molecules, the earlier workers only calculated this frequency, but did not record it.     

Raman and infrared spectra of ethylene glycol

The Raman spectrum of ethylene glycol has been investigated in the liquid and solid states and also in aqueous solutions. The infrared absorption spectrum of the liquid has been recorded. 27 Raman lines and 17 infrared maxima in the liquid state and 20 Raman lines in the solid state have been reported. Detailed vibrational assignments have been given. Two strong polarised Raman lines of the liquid which have no corresponding infrared absorption bands, and which disappear on solidification, have been attributed to the trans configuration of the glycol molecule. From a comparative study of the various spectra, it is concluded that in the liquid state, glycol exists as a mixture of the two rotational isomers (trans and gauche) whereas in the solid state only the gauche form is present. In very dilute aqueous solutions, the predominant molecular form is the gauche form.     

Raman and infrared spectra of ammonium selenate and lithium ammonium selenate

The Raman and infrared absorption spectra of (NH₄)₂ SeO₄, (ND₄)₂ SeO₄ and Li (NH₄) SeO₄ have been recorded at 300° K; while the spectra of the non-deuterated compounds have been recorded at 110° K also. (NH₄)₂ Se0₄ crystal exhibits 33 Raman lines, while LiNH₄SaO₄ shows 30 Raman lines at 300° K. Proper assignments have been given to the observed vibration frequencies. The SeO₄ ^?? ions and the (NH₄)⁺ ions are found to be highly distorted in these selenates. There is lowering of the N-H vibration frequencies due to hydrogen bonding. The present spectroscopic investigations do not reveal the existence of any phase transition in these selenates in the temperature region investigated.     

Potential constants and mean amplitudes of vibrations of N-methyl acetamide

A normal co-ordinate treatment based on general quadratic forcefield has been applied to N-methyl acetamide molecule. In these calculations, the structure parameters of N-methyl acetamide, as given recently by Katzet al., and the Raman and infra-red data obtained by the authors are used and the potential constants have been obtained. The potential energy distribution among the various symmetry co-ordinates of each normal vibration and the mean amplitudes of vibrations have been calculated.