Products of the gas-phase reaction of OH radicals with cyclohexane: Reactions of the cyclohexoxy radical

Products of the gas-phase reactions of OH radicals with cyclohexane and cyclohexane-d(12) in the presence of NO have been investigated using gas chromatography with flame ionization detection, combined gas chromatography-mass spectrometry, and in situ direct air-sampling atmospheric pressure ionization tandem mass spectrometry (API-MS). Cyclohexanone and cyclohexyl nitrate (and their deuterated analogues) were identified and quantified, with formation yields of cyclohexanone and cyclohexyl nitrate from the cyclohexane reaction of 0.321 +/- 0.035 and 0.165 +/- 0.021, respectively, and with cyclohexanone-d(10) and cyclohexyl nitrate d(11) formation yields from the cyclohexane-d(12) reaction of 0.156 +/- 0.017 and 0.210 +/- 0.025, respectively. The remaining products must arise from the decomposition and/or isomerization reactions of the intermediate cyclohexoxy radical. API-MS analyses of the cyclohexane and cyclohexane-d(12) reactions showed the formation of cyclohexanone and cyclohexyl nitrate (and their deuterated analogues), together with ion peaks attributed to HC(O)CH2CH2CH2CH2CH2ONO2 (formed from NO addition to the HC(O)CH2CH2CH2CH2CH2OO. radical formed after decomposition of the cyclohexoxy radical) and HC(O)CH2CH(OH)CH2CH2CHO (formed after isomerization of the HC(O)CH2CH2CH2CH2CH2O. radical). No evidence for isomerization of the cyclohexoxy radical was obtained from the API-MS analyses. The reactions of the cyclohexoxy radical are discussed and the data extended to the reactions of the cyclopentoxy and cycloheptoxy radicals formed from cyclopentane and cycloheptane.