ANALYSIS OF RADICALS FROM FLAMES BY SCAVENGING WITH DIMETHYL DISULFIDE

Larger hydrocarbon radicals in flames, which are difficult to detect by optical methods, can be analyzed quantitatively by radical scavenging with dimethyl disulfide in the condensed phase. - Gas samples taken from a sooting ethyne/oxygen flame by a nozzle beam were frozen at liquid-N2-temperature on the inner surface of a hollow sphere simultaneously with the radical scavenger dimethyl disulfide. The latter was admitted in large excess as a gas and was condensed uniformly on the inner wall of the sphere. The mixture of condensable stable flame products and scavenging products in the excess CH3SSCH3 was separated and identified by GC/MS. - Larger hydrocarbons (C(x)H(y), x greater-than-or-equal-to 6) condensed quantitatively. H, CH3, C4H3 and the phenyl radical were scavenged as mono(methylthio) compounds; C2 and the carbenes CH2, C3H2, C5H2 yielded bis(methylthio) compounds; other bis(methylthio) compounds observed were C(2n)H2(SCH3)2 with n = 1, 2, 3 and 4. CH, C3H and C2H3 were identified by the respective tris(methylthio) compounds. Any consecutive reactions of radicals with stable flame products and their recombinations in the cold trap were suppressed by their scavenging reaction.