The kinetics of the reactions of C₂ (a³∏ _u) with alcohols

The reactions of C₂ (a³∏_u) radicals with a series of alcohols have been studied at about 6.5 Torr total pressure and room temperature using the pulsed laser photolysis/laser-induced fluorescence technique. The relative concentration of C₂ (a³∏ _u) radicals, which are generated via the photolysis of C ₂Cl₄ with the focused output from the fourth harmonic of a Nd:YAG laser (266 nm), was monitored by laser-induced fluorescence (LIF) in the (0, 0) band of the C₂ (d³∏_g←a ³∏_u) transition at 516.5 nm. Under pseudo-first-order conditions, we measured the time evolution of C₂ (a ³∏_u) and determined the rate constants for reactions of C₂ (a³∏_u) with alcohols. The rate constants increase linearly with the number of C atoms in the alcohols. All of them are larger than those for reactions of C₂ (a³∏ _u) with alkanes (C₂-C₅). Based on the bond dissociation energy and linear free energy correlations, we believe the reactions of C₂ (a³∏_u) with alcohols proceed via the mechanism of hydrogen abstraction. The experimental results show that the H-atom on the C-H bonds is activated at the presence of the OH substituent group in the alcohol molecule. The theoretical calculations for the reaction of C₂ (a³∏_u) with methanol also support these hypotheses.