The radiation-induced fragmentation of high-molecular-weight isoprenoid hydrocarbons present in high-boiling petroleum fractions

The radiation-induced fragmentation of squalane, phytane and high-molecular-weight isoprenoid hydrocarbons present in high-boiling petroleum fractions was investigated. The structure of the isoprenoids was determined by 13C NMR spectroscopy, and the identification and quantification of their radiolysis products was performed by gas chromatography. It was found that the vast majority of high-molecular-weight isopranes present in the samples have a regular (i.e., head-to-tail) structure and that their terminal groups have methyl branches at positions 2,6,10,…; 3,7,11,…; 4,8,12,…and 6,10,14,…The ratio of radiation-chemical yields of fragment isoprenoids to that of n-alkanes (G(isop)/G(n-alkane)) correlates well with the isoprenoid content in the sample. Based on the concentration distribution of radiolytic products, an attempt was made to reconstruct the quantitative ratio of isoprenoid end groups in the samples.