ISSN:
0377-0486
Keywords:
Chemistry
;
Analytical Chemistry and Spectroscopy
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
,
Physics
Notes:
The Raman spectra of 14 positional isomers of carboxylic acids esters with 17 skeletal atoms, CH3(CH2)m-1COO(CH2)n-1CH3(CmCOOCn) with m + n = 15 and m = 1 - 14, have been measured in the crystalline state at liquid nitrogen temperature. The relationship between the observed wavenumbers of the characteristic bands and the positions of the - C(=O) - O - group in the molecular chain was examined. All of the positional isomers of CmCOOCn with m + n = 15 exhibit a strong LAM-1 band in the region between 147 and 136 cm-1. The LAM-1 wavenumbers for the isomers which have the - C(=O) - O - group almost in the middle of the molecular chain are slightly higher (147 - 143 cm-1) than those for the isomers which have the same group almost at the end of the chain. In order to elucidate the observed LAM-1 wavenumbers, the Raman spectra of two homologous series of esters, C5COOCn and C6COOCn, were examined. All isomers of CmCOOCn give a strong band at about 1135 cm-1 assignable to the k = 1 mode of the C - C stretching vibrations. Some of the isomers give an additional k = 1 band at about 1125 cm-1. The isomers of CmCOOCn, which exhibit the two k = 1 bands, have the - C(=O) - O - group almost in the middle of the molecular chain, and appear to give the LAM-1 band at the higher wavenumbers. In the crystalline state all of the esters examined take the all-trans conformation with the - C(=O) - O - group part incorporated.
Additional Material:
5 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/jrs.1250260203
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