Vibrational spectra in the carbonyl stretching region of isotopomers of formamide in the gaseous and liquid states

Article abstract of DOI:10.1016/0584-8539(94)00238-X

IR spectra in the carbonyl stretching region of six isotopomers of formamide (HCONH2, HCOND2, DCONH2, DCOND2, H¹³CONH2, and HCO¹⁵NH2) in the gaseous state at a temperature of 120 deg C are presented.From the frequency shifts observed it is concluded that the carbonyl stretching band is largely a stretching of the carbonyl group with only minor contributions from the CN stretching and CH bending vibrations.Calculations with a known force field confirm these results.However, some discrepancies between the observed and calculated frequencies are observed.This is most likely due to a Fermi resonance in some of the isotopomers.Changing the gas phase values of the CO and CN stretching diagonal force constants only gives satisfactory agreement between the calculated frequencies and the observed frequencies in the liquid state.Upon heating, the Raman carbonyl bands of neat liquid HCONH2, neat liquid HCOND2, and an equimolar mixture of the two shift to different extents.This is most likely due to differences in the carbonyl stretching normal coordinate. - Keywords: Carbonyl; Formamide; Gas; Isotopomer; Liquid