Atmospheric chemistry of cyclohexane: UV spectra of c-C{sub 6}H{sub 11}{sup {sm_bullet}} and (c-C{sub 6}H{sub 11})O{sub 2}{sup {sm_bullet}} radicals, kinetics of the reactions of (c-C{sub 6}H{sub 11})O{sub 2}{sup {sm_bullet}} radicals with NO and NO{sub 2}, and the fate of the alkoxy radical (c-C{sub 6}H{sub 11})O{sup {sm_bullet}}
- Risoe National Lab., Roskilde (Denmark). Dept. of Atmospheric Chemistry Plant Biology and Biogeochemistry
- Ford Motor Co., Dearborn, MI (United States)
Alkanes constitute a significant fraction of automotive fuels, vehicle emissions, and air pollution in urban areas. Atmospheric oxidation of alkanes is initiated primarily via attack by OH radicals giving alkyl radicals which then add O{sub 2} to give alkyl peroxy radicals. Subsequent reactions of the alkyl peroxy radicals determine the atmospheric degradation mechanism, and hence ozone forming potential, of organic compounds. A pulse radiolysis technique was used to measure the UV absorption spectra of c-C{sub 6}H{sub 11}{sup {sm_bullet}} and (c-C{sub 6}H{sub 11})O{sub 2}{sup {sm_bullet}} radicals over the ranges 230--290 and 220--300 nm, {sigma}(c-C{sub 6}H{sub 11}{sup {sm_bullet}}){sub 250 nm} = (7.0 {+-} 0.8) {times} 10{sup {minus}18} and {sigma}((c-C{sub 6}H{sub 11})O{sub 2}{sup {sm_bullet}}){sub 250 nm} = (5.7 {+-} 0.6) {times} 10{sup {minus}18} cm{sup 2} molecule{sup {minus}1}. The rate constant for the self-reaction of c-C{sub 6}H{sub 11}{sup {sm_bullet}} radicals was {kappa}{sub 3} = (3.0 {+-} 0.4) {times} 10{sup {minus}11} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}. Rate constants for reactions of (c-C{sub 6}H{sub 11})O{sub 2}{sup {sm_bullet}} radicals with NO and NO{sub 2} were {kappa}{sub 4} = (6.7 {+-} 0.9) {times} 10{sup {minus}12} and {kappa}{sub 5} = (9.5 {+-} 1.5) {times} 10{sup {minus}12} cm{sup 3} molecule{sup {minus}1} s{sup {minus}1}, respectively. FTIR-smog chamber techniques were used to record the IR spectrum of the peroxynitrate (c-C{sub 6}H{sub 11})O{sub 2}NO{sub 2}. determine that the reaction between (c-C{sub 6}H{sub 11})O{sub 2}{sup {sm_bullet}} radicals and NO produces a (16 {+-} 4)% yield of the nitrate (c-C{sub 6}H{sub 11})ONO{sub 2}, and study the atmospheric fate of cyclohexoxy radicals. Decomposition via C-C bond scission and reaction with O{sub 2} are competing fates of the cyclohexoxy radical. In 700--750 Torr total pressure at 296 {+-} 2K, the rate constant ratio {kappa}{sub decomp}/{kappa}{sub O{sub 2}} = (8.1 {+-} 1.5) {times} 10{sup 18} molecule cm{sup {minus}3}. At 296 K in 1 atm of air, 61% of cyclohexoxy radicals decompose and 39% react with O{sub 2}.
- OSTI ID:
- 347658
- Journal Information:
- Journal of Physical Chemistry A: Molecules, Spectroscopy, Kinetics, Environment, amp General Theory, Vol. 103, Issue 15; Other Information: PBD: 15 Apr 1999
- Country of Publication:
- United States
- Language:
- English
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