The kinetics of the reactions of C2 (a 3pi(u)) with alcohols.

The reactions of C2 (a 3pi(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 (a 3pi(u)) radicals, which are generated via the photolysis of C2Cl4 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 (d 3pi(g)<--a 3pi(u)) transition at 516.5 nm. Under pseudo-first-order conditions, we measured the time evolution of C2 (a 3pi(u)) and determined the rate constants for reactions of C2 (a 3pi(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 (a 3pi(u)) with alkanes (C1-C5). Based on the bond dissociation energy and linear free energy correlations, we believe the reactions of C2 (a 3pi(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 (a 3pi(u)) with methanol also support these hypotheses.