INTERACTIONS IN LIQUID-MIXTURES OF FORMAMIDE ISOTOPOMERS STUDIED BY RAMAN-SPECTROSCOPY

Recently, anomalies concerning both intensities and peak positions of Raman bands in the carbonyl stretching region of liquid mixtures of di fferent isotopomers of formamide were reported. More detailed investig ations have now been performed for liquid mixtures of HCONH2 and (HCON H2)-C-13, and Raman spectra of mixtures of DCONH2 and DCOND2 in the ca rbonyl stretching region are presented. In the system DCONH2-DCOND2, c ollapse of the isotropic carbonyl bands was observed in the mixtures a s previously reported for HCONH2-NCOMD(2) and NCOND2-DCOND2. The syste m HCONH2-(HCONH2)-C-13 shows anomalous intensities compared with those expected for simple binary mixtures. However, this system does not sh ow collapsing carbonyl bands in the isotopomeric mixtures. The phenome non of collapsing bands can be explained in terms of a model known as mutual entrainment.