Normal and branched alkanes from cast skins of the grasshopper Schistocerca vaga (Scudder)

Abstract

Gas-liquid chromatographic and mass spectral analyses of the hydrocarbons from cast skins of the grasshopper Schistocerca vaga (Scudder) demonstrated the presence of four homologous series of alkanes: n-alkanes (35%), monomethylalkanes (24%), dimethylalkanes (35%), and trimethylalkanes (3%). The methyl branches were located towards the center of the molecule, and no 2- or 3-methylalkanes were detected by mass spectrometry. The branched alkanes occurred as isomeric mixtures with the methyl group(s) usually located on carbon atom 11, 13, 15, or 17. In the di- and trimethylalkanes, the branch points had isoprenoid spacing. Of the total hydrocarbons, the major component of the n-alkane series was nonacosane, 23%; of the monomethylalkanes, it was 11-, 13-, 15-, and 17-methylpentatriacontanes, 13%; of the dimethylalkanes, 9,13-, 11,15-, 13,17-, and 15,19-dimethylpentatriacontanes, 20%; and of the trimethylalkanes, 11,15,19- and 13,17,21-trimethylpentatriacontanes, 1%.