The temperature dependence of the rate coefficients for the OH radical reactions with toluene, benzene, o-cresol, m-cresol, p-cresol, phenol, and benzaldehyde were measured by the competitive technique under simulated atmospheric conditions over the temperature range 258-373 K. The relative rate coefficients obtained were placed on an absolute basis using evaluated rate coefficients for the corresponding reference compounds. Based on the rate coefficient k(OH + 2,3-dimethylbutane) = 6.2 X 10-l' cm3 molecule-' s-', independent of temperature, the rate coefficient for toluene k o~ = 0.79cm3 molecule-l s-l over the temperature range 284-363 K was determined. The following rate coefficients in units of cm3 molecule-' s-' were determined relative to the rate coefficient k(OH + lifetimes of the aromatic compounds studied were calculated relative to that for l,l,l-trichlorethane = 6.3 years a t 277 K. The lifetimes range from 6 h for n-cresol to 15.5 days for benzene. 0

The transformations of acetylene, chloroacetylene, 1,1dichloroethene (DCE), and cisand trans-DCE mediated by cobalamin in the presence of titanium(III) citrate were investigated at pH 8 and 22 °C. Acetylene quantitatively reacted to ethene via vinylcobalamin as the proposed intermediate. Chloroacetylene reacted to acetylene and vinyl chloride. Proposed intermediates are ethynylcobalamin and vinylcobalamin, respectively. The principal initial reaction of chloroacetylene formed ethynylcobalamin which decomposed to acetylene. The proposition for ethynyl-and vinylcobalamin formation is based on fitting reaction models to kinetic data. Kinetic modeling suggests half-lives for ethynyl-and vinylcobalamin of 1.4 and 251 h, respectively. 1,1-Dichloroethene reacted to approximately 20% volatiles (ethene, ethane, vinyl chloride, and acetylene) and 80% unidentified nonvolatile products. cisand trans-DCE transformed slowly and produced small yields of vinyl chloride, ethene, and ethane.

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