Synthetic methyl- and dimethylalkanes : Kovats Indices, [(13)C]NMR and mass spectra of some methylpentacosanes and 2,X-dimethylheptacosanes.

All possible isomeric mono-methylpentacosanes as well as 2,6-, 2,8-, 2,10-, 2,12-, and 2,14-dimethylheptacosane were synthesized. The [(13)C]NMR shifts and the Kovats indices were determined, and the relationship to separation of isomeric mixtures of insect cuticular waxes are discussed. When several homologous series of hydrocarbon isomeric mixtures are to be separated, it is not practical to attempt complete gas-chromatographic separation of all possible isomers. The mass spectra of the 2,X-dimethylheptacosanes are presented and discussed.