Soot produced from the combustion of fossil fuels, widely distributed in the atmosphere, is significantly different from most carbons for which the surface structure and/or reactivity have been studied. The composition and surface structure of soot derived from the combustion of n-hexane have been examined by FT-IR, Raman, UC CP/MAS NMR, and EPR spectroscopies as well as through desorption measurements. Carbon-oxygen functionalities on the fresh carbon surface include acid anhydride, a carbonyl conjugated with an aromatic segment, an alkyl-ketone, and aryl ether linkages. Also present, confirmed by isotopic substitution, is a quantity of unsaturated C-H, dependent upon the combustion conditions. The degree of aromaticity and the graphitic nature of this soot have been determined.

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Successive extraction of soluble components of hexane soot with a suite of solvents has been followed by CGC/MS, FT-IR, UV/Vis, fluorescence, and NMR spectroscopic analysis of these extracts. From these studies, additional understanding of the structure and reactivity of this material has emerged. A significant portion of the soot is extractable as polynuclear aromatic and aliphatic compounds, while the nonextractable solid structure, with both aromatic and aliphatic portions, contains such carbon-oxygen functionalities as acid anhydride, carbonyl, and ether linkages. A model of hexane soot as formed in flame is proposed on the basis of this work.