The characterization of the surface of elemental carbon (soot) generated by the combustion of hexane, taken as a model for petroleum fuel, has been accomplished with Fourier transform infrared (FT-IR) spectroscopy combined with thermal 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 conditions of soot formation. The reactivity of this surface toward some oxides of sulfur and nitrogen also has been studied by FT-IR. SO2 reacts selectively with surface groups in the absence of 02 to form sulfate. The formation of carboxylate and nitro groups, through the reaction of NO2 with the functional groups of the soot surface, has been observed.