title: Mass spectrometric monitoring of oxidation of aliphatic C6-C8 hydrocarbons and ethanol in low pressure oxygen and air plasmas.
abstract: Experimental and theoretical studies on the oxidation of saturated hydrocarbons (n-hexane, cyclohexane, n-heptane, n-octane and isooctane) and ethanol in 28 Torr O2or air plasma generated by a hollow cathode discharge ion source were made. Ions corresponding to [M + 15]+and [M + 13]+in addition to [M - H]+and [M - 3H]+were detected as major ions where M is the sample molecule. The ions [M + 15]+and [M + 13]+were assigned as oxidation products, [M - H + O]+and [M - 3H + O]+, respectively. By the tandem mass spectrometry analysis of [M - H + O]+and [M - 3H + O]+, H2O, olefins (and/or cycloalkanes) and oxygen-containing compounds were eliminated from these ions. Ozone as one of the terminal products in the O2plasma was postulated as the oxidizing reagent. As an example, the reactions of C6H14+•with O2and of C6H13+(CH3CH2CH+CH2CH2CH3) with ozone were examined by density functional theory calculations. Nucleophilic interaction of ozone with C6H13+leads to the formation of protonated ketone, CH3CH2C(=OH+)CH2CH2CH3. In air plasma, [M - H + O]+became predominant over carbocations, [M - H]+and [M - 3H]+. For ethanol, the protonated acetic acid CH3C(OH)2+(m/z 61.03) was formed as the oxidation product. The peaks at m/z 75.04 and 75.08 are assigned as protonated ethyl formate and protonated diethyl ether, respectively, and that at m/z 89.06 as protonated ethyl acetate. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu, Yamanashi, 400-8511, Japan.|Institute of Ion-Plasma and Laser Technologies, Durmon Yoli Street 33, Tashkent, 100125, Uzbekistan.
authors.forename: Dilshadbek T
authors.initials: DT
authors.lastname: Usmanov
authors.affiliation: Interdisciplinary Graduate School of Medicine and Engineering, University of Yamanashi, Takeda-4, Kofu, Yamanashi, 400-8511, Japan.
authors.forename: Lee Chuin
authors.initials: LC
authors.lastname: Chen
authors.affiliation: Clean Energy Research Center, University of Yamanashi, Takeda-4, Kofu, Yamanashi, 400-8511, Japan.
authors.forename: Kenzo
authors.initials: K
authors.lastname: Hiraoka
authors.affiliation: Kyushu Okinawa Agricultural Research Center, National Agriculture and Food Research Organization, 496 Izumi, Chikugo, Fukuoka, 833-0041, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Wada
authors.affiliation: Plant Biophysics/Biochemistry Research Laboratory, Faculty of Agriculture, Ehime University, 3-5-7 Tarumi, Matsuyama, 790-0905, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Nonami
authors.affiliation: Department of Material Science, Nara Institute of Science and Technology, Takayama-cho, 8916-5, Ikoma, Nara, 630-0101, Japan.
authors.forename: Shinichi
authors.initials: S
authors.lastname: Yamabe
keywords: DFT calculations; air plasma; alkanes; hollow cathode discharge; oxidation; oxygen plasma; ozone