VIBRATIONAL SPECTRA, NORMAL VIBRATIONS AND ROTATIONAL ISOMERISM OF ETHYL ACETATE AND THREE DEUTERATED ANALOGUES

Article abstract of DOI:10.1016/0022-2860(88)80246-1

IR and Raman spectra of ethyl acetates, CH3COOC2H5, CD3COOC2H5, CH3COOC2D5 and CD3COOC2D5 in the liquid and crystalline states have been recorded in the 3500-200 cm^-1 region.These spectra are analysed on the basis of spectral comparison both among themselves and with spectra of the trichloro analogues CCl3COOC2H5 and CCl3COOC2D5 previously studied.All the ethyl acetates in the crystalline state give two completely separated carbonyl stretching Raman bands, suggesting that two, or an even number of molecules, exist in the crystal unit.Liquid-state spectra exhibit many band pairs arising from the trans-trans and trans-gauche conformers around CX3CO-O-CX2CX3 axes (X=H and D) and the bands of the trans-trans conformer persist in the crystalline state.Normal coordinate calculations for the four species have been carried out on the two isomeric models using an MVIB program.The results explain wavenumber shifts on deuteration and the nature and separation of band pairs satisfactorily, and suggest that a large amount of vibrational coupling exists among skeletal stretching vibrations.