A Local Mode Description of the CH-Stretching Overtone Spectra of the Cycloalkanes and Cycloalkenes
The overtone spectra of the cycloalkanes, cyclopentane to cyclooctane, and three cycloalkenes (cyclopentene, cyclohexene, and cycloheptene) are measured in the liquid phase up to ∆vCH = 7 for the cycloalkanes and up to ∆vCH = 6 for the cycloalkenes. The principal bands in the cyclopentane and cyclohexane spectra correspond to axial and equatorial CH bonds. We demonstrate that these bands correspond to the properties of the CH bonds in the static limit, and for cyclopentane introduce a possible definition for axial and equatorial bonds. Single bands are observed in cycloheptane and cyclooctane and their structures explained. The overtone bands of the cycloalkenes are principally composed of two peaks, one corresponding to the olefin hydrogens and one corresponding to the methylene hydrogens. The methylene peak shows some doublet structure in cyclopentene and cyclohexene which can be understood on the same basis as in the corresponding saturated molecules. The local mode frequencies and diagonal local mode anharmonicity constants are obtained from an analysis of the spectral data. © 1980, American Chemical Society. All rights reserved.
Henry, BR; Hung, IF; MacPhail, RA; Strauss, HL
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