| Title: | "Surprising formation of p-cymene in the oxidation of alpha-pinene in air by the atmospheric oxidants OH, O3, and NO3" |
| Author(s): | Gratien A; Johnson SN; Ezell MJ; Dawson ML; Bennett R; Finlayson-Pitts BJ; |
| Address: | "Department of Chemistry, University of California Irvine, Irvine, California 92697-2025, United States" |
| ISSN/ISBN: | 1520-5851 (Electronic) 0013-936X (Linking) |
| Abstract: | "Anthropogenic sources release into the troposphere a wide range of volatile organic compounds (VOCs) including aromatic hydrocarbons, whose major sources are believed to be combustion and the evaporation of fossil fuels. An important question is whether there are other sources of aromatics in air. We report here the formation of p-cymene [1-methyl-4-(1-methylethyl) benzene, C6H4(CH3)(C3H7)] from the oxidation of alpha-pinene by OH, O3, and NO3 at 1 atm in air and 298 K at low (<5%) and high (70%) relative humidities (RH). Loss of alpha-pinene and the generation of p-cymene were measured using GC-MS. The fractional yields of p-cymene relative to the loss of alpha-pinene, Delta [p-cymeme]/Delta [alpha-pinene], were measured to range from (1.6+/-0.2)x10(-5) for the O3 reaction to (3.0+/-0.3)x10(-4) for the NO3 reaction in the absence of added water vapor. The yields for the OH and O3 reactions increased by a factor of 4-8 at 70% RH (uncertainties are +/-2s). The highest yields at 70% RH for the OH and O3 reactions, approximately 15 times higher than for dry conditions, were observed if the walls of the Teflon reaction chamber had been previously exposed to H2SO4 formed from the OH oxidation of SO2. Possible mechanisms of the conversion of alpha-pinene to p-cymene and the potential importance in the atmosphere are discussed" |
| Keywords: | Air Pollutants/analysis/*chemical synthesis Atmosphere/chemistry Bicyclic Monoterpenes Cymenes Hydroxyl Radical/*chemistry Monoterpenes/analysis/*chemical synthesis/*chemistry Nitrogen Oxides/*chemistry Oxidants/chemistry Ozone/*chemistry Volatile Organic; |
| Notes: | "MedlineGratien, Aline Johnson, Stanley N Ezell, Michael J Dawson, Matthew L Bennett, Raffeal Finlayson-Pitts, Barbara J eng Research Support, U.S. Gov't, Non-P.H.S. 2011/03/17 Environ Sci Technol. 2011 Apr 1; 45(7):2755-60. doi: 10.1021/es103632b. Epub 2011 Mar 15" |
