Evidence for direct intermolecular interactions as an origin of the hydration shifts of the C—H stretching vibrations: 1,4-dioxane/water system
✍ Scribed by Keiji Kamogawa; Teizo Kitagawa
- Publisher
- Elsevier Science
- Year
- 1991
- Tongue
- English
- Weight
- 526 KB
- Volume
- 179
- Category
- Article
- ISSN
- 0009-2614
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✦ Synopsis
Frequency shifts of the C-H stretching vibrations ( vCH ) of 1,4dioxane (DX) and dimetltylsulfoxide in aqueous solutions were observed as a function of concentration using a dual-beam difference Raman apparatus. A nonlinear positive increase of the shift was observed upon dilution for the vcw modes of DX, similar to the case of alcohol/water mixtures, while negative and zero shifts were observed for its C-O and C-C stretching modes, respectively. The shift of the vcn mode is not the secondaty effect arising from a change in hydrogen bonding at oxygen. The Au, versus & curve of the ucn mode exhibited a deep minimum around x1=0.08, indicating the formation of molecular assemblies of DX with the C-H groups inside in the concentration region of 0.08 <~*<0.5 and its collapse into molecular dispersion at & <0.08. The transfer shift from HZ0 to D1O was significantly smaller for DX than for acetone and acotonitrile.