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Re-examination of the Effect of Aprotic Solvents Upon the Fundamental Vibrational Peak of the Carbonyl Group in 1,1,3,3-Tetramethylurea

Volume 53, Number 1 (Jan. 1999) Page 29-32

Kolling, Orland W.

The 1650 cm-1 IR absorption band for the fundamental vibration of the C = O group in tetramethylurea (TMU) exhibits a substantial solvent-induced shift in polar and nonpolar aprotic solvents at 298 K. Earlier studies have rationalized the upsilon max (C = O) shifts in terms max of the empirical Gutmann acceptor numbers (ANs) for the solvents or the Kirkwood parameter in dielectric permittivity (epsilon). With a larger set of test data, other reaction field models are now compared which incorporate alternative continuum functions as elements in the formulation of an SCRF-MO perturbation description for the aprotic solvent effect upon the upsilon max (C = O) of TMU. The magnitude max of the band shift appears to depend on both the solvent dipolarity and solvent polarizability, with the first being the dominant factor in the more reliable model.