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-C 6 H 11 • and (c-C 6 H 11 )O 2 • radicals over the ranges 230−290 and 220−300 nm, σ(c-C 6 H 11 • ) 250 nm = (7.0 ± 0.8) × 10 -18 and σ((c-C 6 H 11 )O 2 • ) 250 nm = (5.7 ± 0.6) × 10 -18 cm 2 molecule -1 . The rate constant for the self-reaction of c-C 6 H 11 • radicals was k 3 = (3.0 ± 0.4) × 10 -11 cm 3 molecule -1 s -1 . The addition reaction of c-C 6 H 11 • radicals with O 2 proceeds with a rate constant k 2 = (1.3 ± 0.2) × 10 -11 cm 3 molecule -1 s -1 . Rate constants for reactions of (c-C 6 H 11 )O 2 • radicals with NO and NO 2 were k 4 = (6.7 ± 0.9) × 10 -12 and k 5 = (9.5 ± 1.5) × 10 -12 cm 3 molecule -1 s -1, respectively. FTIR−smog chamber techniques were used to record the IR spectrum of the peroxynitrate (c-C 6 H 11 )O 2 NO 2, determine that the reaction between (c-C 6 H 11 )O 2 • radicals and NO produces a (16 ± 4)% yield of the nitrate (c-C 6 H 11 )ONO 2, 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) × 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.