Atmospheric chemistry of cyclohexane:: UV spectra of c-C6H11• and (c-C6H11)O2• radicals, kinetics of the reactions of (c-C6H11)O2• radicals with NO and NO2, and the fate of the alkoxy radical (c-C6H11)O•

A pulse radiolysis technique was used to measure the UV absorption spectra of c-C6H11. and (c-C6H11)O-2(.) radicals over the ranges 230-290 and 220-300 nm, sigma(c-C6H11.)(250 nm), = (7.0 +/- 0.8) x 10(-18) and sigma((c-C6H11)O-2(.))(250 nm) = (5.7 +/- 0.6) x 10(-18) cm(2) molecule(-1). The rate constant for the self-reaction of c-C6H11. radicals was k(3) = (3.0 +/- 0.4) x 10(-11) cm(3) molecule(-1) s(-1). The addition reaction of c-C6H11. radicals with O-2 proceeds with a rate constant k(2) = (1.3 +/- 0.2) x 10(-11) cm(3) molecule(-1) s(-1). Rate constants for reactions of (c-C6H11)O-2(.) radicals with NO and NO2 were k(4) = (6.7 +/- 0.9) x 10(-12) and k(5) = (9.5 +/- 1.5) x 10(-12) cm(3) molecule(-1) s(-1), respectively. FTIR-smog chamber techniques were used to record the IR spectrum of the peroxynitrate (c-C6H11)O2NO2, determine that the reaction between (c-C6H11)O-2(.) radicals and NO produces a (16 +/- 4)% yield of the nitrate (c-C6H11)ONO2, and study the atmospheric fate of cyclohexoxy radicals. Decomposition via C-C bond scission and reaction with O-2 are competing fates of the cyclohexoxy radical. In 700-750 Torr total pressure at 296 +/- 2K, the rate constant ratio k(decomp)/k(O2) = (8.1 +/- 1.5) x 10(18) molecule cm(-3). At 296 K in 1 atm of air, 61% of cyclohexoxy radicals:decompose and 39% react with O-2. These results are discussed with respect to the literature data concerning the atmospheric chemistry of cyclohexane and analogous compounds.