Pyrogenesis of Aromatic Hydrocarbons Present in Cigarette Smoke II: Pyrolytic Products of some Representative Constituents of the Hexane Soluble Fraction of Tobacco

In continued studies to reevaluate the contribution of the hexane-soluble fraction of flue-cured tobacco to the formation of aromatic compounds, especially polynuclear aromatic hydrocarbons, present in cigarette smoke, some compounds representative of that fraction have been pyrolyzed (860°C, N₂). The straight chain saturated compounds, n-hexane, stearic acid, and dotriacontane, produced pyrolysates distinguished by relatively low yields of total neutrals and the absence of any significant quantities of aromatic products with alkyl side chains. Compounds containing double bonds, such as the unsaturated fatty acid, linolenic acid and its methyl ester, and the polyene squalene, which like phytol is also characterized by methyl groups on the chain, produced relatively higher yields of neutral products, including alkyl-substituted aromatic hydrocarbons. Phytol, of course, also exhibited this tendency. Pyrolysis of the plant sterol, b-sitosterol, produced the greatest amounts of phenanthrene and BaP. Estimates of BaP levels in pyrolysates indicate that phytol, in addition to the above mentioned sterol, is a relatively effective high temperature precursor of this important carcinogen. The hexane solubles of flue-cured tobacco were shown to produce BaP in levels intermediate to the least effective (stearic acid) and most effective (b-sitosterol) precursor examined.