A Positive Halphen Test with a Non-Cyclopropenoid Compound ,

Abstract

THE Halphen color test is a reaction considered characteristic of the naturally occurring cyclopropenoid fatty acids (Carter and Frampton, 1964; Magne, 1965). Halphen reactions with sterculene (1,2-dioctylcyclopropene) and sterculyl alcohol, using the method of Klaus and Deutschman (1960), did not produce deviations from the normal behavior of the Halphen reagents on cyclopropenoid containing oils (Nordby et al., 1962) indicating that the color of the Halphen test is not affected by the carboxyl group of the fatty acid. Apparently, the methylene of the cyclopropene ring must be unsubstituted to give a positive test, as methyl w-(2-n-octyl-3-carbethoxycycloprop-1-enyl) octanoate failed to give the reaction (Brooke and Smith, 1957).This communication reports that the Halphen test carried out in pyridine as the solvent gives an intense red color with the allenic compound ethyl-2,3-decadienoate. The Halphen test with the allenic compound methyl-1,2-nonadiene-3-carboxylate results in a reddish-orange color. The preparation, isolation and structure elucidation of these…