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Anal Chem

Title:		Gas-phase infrared spectroscopy for determination of double bond configuration of monounsaturated compounds
Author(s):		Attygalle AB; Svatos A; Wilcox C; Voerman S;
Address:		"Baker Laboratory, Department of Chemistry, Cornell University, Ithaca, New York 14853"
Journal Title:		Anal Chem
Year:		1994
Volume:		66
Issue:		10
Page Number:		1696 - 1703
DOI:		10.1021/ac00082a016
ISSN/ISBN:		0003-2700 (Print) 0003-2700 (Linking)
Abstract:		"Gas-phase Fourier-transform infrared spectra allow unambiguous determination of the configuration of the double bonds of long-chain unsaturated compounds bearing RCH=CHR' type bonds. Although the infrared absorption at 970-967 cm-1 has been used previously for the identification of trans bonds, the absorption at 3028-3011 cm-1 is conventionally considered to be incapable of distinguishing cis and trans isomers. In this paper, we present a large number of gas-phase spectra of monounsaturated long-chain acetates which demonstrate that an absorption, highly characteristic for the cis configuration, occurs at 3013-3011 cm-1, while trans compounds fail to show any bands in this region. However, if a double bond is present at the C-2 or C-3 carbon atoms, this cis=CH stretch absorption shows a hypsochromic shift to 3029-3028 and 3018-3017 cm-1, respectively. Similarly, if a cis double bond is present at the penultimate carbon atom, this band appears at 3022-3021 cm-1. All the spectra of trans alkenyl acetates showed the expected C-H wag absorption at 968-964 cm-1. In addition, the spectra of (E)-2-alkenyl acetates show a unique three-peak 'finger-print' pattern which allows the identification of the position and configuration of this bond. Furthermore, by synthesizing and obtaining spectra of appropriate deuteriated compounds, we have proved that the 3013-3011 cm-1 band is representative of the C-H stretching vibration of cis compounds of RCH=CHR' type"
Keywords:		"Alkenes/*chemistry Gases/analysis Molecular Conformation Pheromones/*chemistry Spectroscopy, Fourier Transform Infrared/methods;"
Notes:		"MedlineAttygalle, A B Svatos, A Wilcox, C Voerman, S eng AI12020/AI/NIAID NIH HHS/ Research Support, U.S. Gov't, P.H.S. 1994/05/15 Anal Chem. 1994 May 15; 66(10):1696-703. doi: 10.1021/ac00082a016"