Detection of the cyclopropane ring and its degree of substitution in long-chain fatty acid esters, by infra-red spectroscopy

Abstract

Inclusion of the cyclopropane ring in long-chain fatty acids during incubation of adipose tissue in the presence of sodium cyclopropanecarboxylate has been proved to occur from measurements on the CH-stretching region of the infra-red spectra of ester samples obtained by chromatographic analysis from the reaction products. The frequencies of the non-paraffinic absorption and the intensity relative to that of the paraffinic absorption show the system present to be a 1,1,2,3-tetra-substituted cyclopropane, such as is found in naturally-occurring cyclopropanes, e.g., pyrethrins. The cis-configuration is probably favoured. The proportion of cyclopropyl corresponds to about one ring per chain of fifteen methylene groups, this confirming the result suggested by radio-carbon counts.