The gas phase reaction between Hg 6(^P^) atoms and methanol, ethanol, isopropanol, and t-butyl alcohol has been examined in a static system at room temperature, under conditions of continuous and intermittent illumination and in the presence of nitric oxide. Evidence has been obtained to demonstrate that the primary process operative in the four cases is, ROH + Hg 6( 5 P 1 ) - RO + H + Hg 6( 1 S q ) The formation of alkoxy radicals was confirmed by observing the formation of the corresponding nitrite when nitric oxide was added. Similarly, the appearance of products known to arise from reactions of HNO, indicated the concomitant formation of hydrogen atoms. The fact that the quantum yield for hydrogen formation under continuous exposure - methanol, 0.46; ethanol, 0.53; isopropanol, 0 . 72 ; and t-butyl alcohol, 0.10 - are less than unity was ascribed to the occurrence of a rapid substrate reforming step involving H-atoms and alkoxy radicals or their immediate sequelae. The conditions of intermittent illumination were found to militate against this quantum-yield-lowering reaction by reducing the mean radical concentration in the system. At light periods of ca. 2 x 10 sec., ^(H-atoms) values observed were 0.89 (methanol), 0.97 (ethanol), 1.0 (isopropanol), and 0.25 (t-butyl alcohol). The subsequent reactions of the primary fragments were found to be abstraction of a hydrogen atom from the ex- carbon atom of the substrate to produce molecular hydrogen, a substrate molecule, and the corresponding hydroxyalkyl radical. The latter species was found to have, in the intermittent illumination studies, a mean lifetime of the order of 0.1 sec. due to the possibility of its undergoing exchange reactions with the substrate before being quenched by hydrogen atoms or in the alternatives of disproportionation or recombination. In the case of t-butyl alcohol, the principal fate of the alkoxy radical produced is unimolecular decomposition into acetone and methyl radicals. In a supplementary investigation, several dark reactions of alcohol vapours were briefly examined.

The photolysis of C2H5SH liquid at 2537 A has been shown to give H2 and C2H5SSC2H5 at equal rates. The photolysis of ethanethiol - methyl disulfide liquid mixtures leads, via a chain reaction involving propagation by attack of thiyl radicals on the disulfide S--S bond, to the formation with high quantum efficiency of CH3SH, C2H5SSC2H5 and, as an intermediate that is consumed after long exposures, CH3SSC2H5. The net result of the sequence of exchange processes is the essentially irreversible conversion of the methyl disulfide into methanethiol. The same overall reaction occurs thermally at room temperature, but the rate is appreciably less than that of the photochemical process. The quantum yields of formation of the unsymmetrical disulfides arising from the photochemically initiated exchange reaction in equimolar mixtures of CH3SSCH3 + n-C3H7SSC3H7, CH3-SSCH3 + C2H5SSC2H5, and C2H5SSC2H5 + n-C3H7SSC3H7 have been determined. In all three types of system examined in this investigation all thiyl radicals can be accounted for stoichiometrically on the basis of exchange and combination reactions alone, indicating negligible disproportionation of these species in condensed phase. (Modified author abstract).