Article ID Journal Published Year Pages File Type
1252326 Vibrational Spectroscopy 2007 7 Pages PDF
Abstract

The isotropic part of the Raman bands corresponding to NH2 bending and ν(CO) stretching modes of formamide (HCONH2) at ∼1593 and 1668 cm−1, respectively, in neat HCONH2 as well as in binary mixtures with methanol (CH3OH) were reinvestigated. Variations of their linewidths exclusively with mole fractions of HCONH2, in the range C = 0.1–0.9 were studied. The linewidth variation of the NH2 bending mode shows a departure from the trend expected on the basis of concentration fluctuation model and this has been explained using a recently suggested empirical model by invoking the concept of microviscosities of the solute, HCONH2 and the solvent, CH3OH. The other peak at ∼1668 cm−1 shows a peculiar variation of the linewidth with concentration having two minima at C = 0.8 and 0.4, which have been explained in terms of formation of hydrogen bonded complexes, NH2HCO⋯HOCH3, and NH2HCO⋯(HOCH3)2 and the two phenomena, namely motional narrowing and diffusion dynamics being simultaneously operative. The equilibrium constants have been evaluated from the spectral data and their variation with total molar concentration has been presented.

Related Topics
Physical Sciences and Engineering Chemistry Analytical Chemistry
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