Effects of dipole interaction and solvation on the C=O stretching band of N,N-dimethylacetamide in nonpolar solutions: Infrared, isotropic and anisotropic Raman measurements

Katsumoto Yukiteru

Tanaka Takeyuki

Ozaki Yukihiro

Hosoi Shinzo

Vibrational Spectroscopy

The concentration dependence of the C=O stretching (nu(C=O)) band of N,N-dimethylacetamide (NdMA) in cyclohexane, n-hexane, and CCl4 has been investigated by infrared (IR) and polarized Raman spectroscopy. For the neat liquid of NdMA, the noncoincidence of the aniso- and isotropic Raman wavenumbers is evident. In the 0.47 M cyclohexane solution of NdMA, the noncoincidence effect almost disappears and the nu(C=O) envelopes in both the Raman and IR spectra are asymmetric to the low-wavenumber side. When the concentration of NdMA decreases from 0.33 to 0.023 M. the peak of these bands slightly shifts to a higher wavenumber and the band shape becomes symmetric. The shape of the nu(C=O) envelope does not show any significant change below 0.023 M. These results Suggest that the asymmetric shape of the nu(C=O) band observed for the 0.33 M cyclohexane solution is associated with the intermolecular interaction among NdMA molecules, which vanishes at around 0.02 M. Spectral changes for the CCl4 solution of NdMA show a similar tendency. However, the shape and peak wavenumber of the nu(C=O) band observed in a highly diluted CCl4 solution (<= 0.023 M) indicate that the solvation effect of CCl4 is more complicated than those of cyclohexane and n-hexane. The analyses of the nu(C=O) band, which is sensitive to the intermolecular interaction between Solutes and between Solute and solvent for NdMA dissolved in nonpolar solvents. Would serve to clarify the electronic property of the molecule in a solution.

N,N-Dimethylacetamide

Infrared spectroscopy

Isotropic and anisotropic Raman spectra

Noncoincidence effects

C=O stretching band

Nonpolar solvents

Chemistry [ 430 ]

eng

Elsevier Science BV

Copyright (c) 2008 Elsevier B.V.

[ISSN] 0924-2031

[DOI] 10.1016/j.vibspec.2008.11.009

[NCID] AA10787250

[DOI] http://dx.doi.org/10.1016/j.vibspec.2008.11.009