Articles | Volume 18, issue 13
Atmos. Chem. Phys., 18, 9297–9328, 2018
Atmos. Chem. Phys., 18, 9297–9328, 2018

Research article 04 Jul 2018

Research article | 04 Jul 2018

Estimation of rate coefficients and branching ratios for gas-phase reactions of OH with aliphatic organic compounds for use in automated mechanism construction

Michael E. Jenkin1,2, Richard Valorso3, Bernard Aumont3, Andrew R. Rickard4,5, and Timothy J. Wallington6 Michael E. Jenkin et al.
  • 1Atmospheric Chemistry Services, Okehampton, Devon, EX20 4QB, UK
  • 2School of Chemistry, University of Bristol, Cantock's Close, Bristol, BS8 1TS, UK
  • 3LISA, UMR CNRS 7583, Université Paris Est Créteil et Université Paris Diderot, Institut Pierre Simon Laplace, 94010 Créteil, France
  • 4Wolfson Atmospheric Chemistry Laboratories, Department of Chemistry, University of York, York, YO10 5DD, UK
  • 5National Centre for Atmospheric Science, University of York, York, YO10 5DD, UK
  • 6Research and Advanced Engineering, Ford Motor Company, SRL-3083, P.O. Box 2053, Dearborn, MI 48121-2053, USA

Abstract. Reaction with the hydroxyl (OH) radical is the dominant removal process for volatile organic compounds (VOCs) in the atmosphere. Rate coefficients for reactions of OH with VOCs are therefore essential parameters for chemical mechanisms used in chemistry transport models, and are required more generally for impact assessments involving the estimation of atmospheric lifetimes or oxidation rates for VOCs. Updated and extended structure–activity relationship (SAR) methods are presented for the reactions of OH with aliphatic organic compounds, with the reactions of aromatic organic compounds considered in a companion paper. The methods are optimized using a preferred set of data including reactions of OH with 489 aliphatic hydrocarbons and oxygenated organic compounds. In each case, the rate coefficient is defined in terms of a summation of partial rate coefficients for H abstraction or OH addition at each relevant site in the given organic compound, so that the attack distribution is defined. The information can therefore guide the representation of the OH reactions in the next generation of explicit detailed chemical mechanisms. Rules governing the representation of the subsequent reactions of the product radicals under tropospheric conditions are also summarized, specifically their reactions with O2 and competing processes.

Short summary
Organic compounds are emitted in large quantities from natural and human-influenced sources. Removal from the atmosphere occurs mainly by reaction with hydroxyl (OH) radicals, and initiates reaction sequences forming pollutants such as ozone and organic particles. Due to their very large number, it is impossible to measure the removal rate for all compounds, and most have to be estimated. An updated and extended estimation method is reported for use in atmospheric models and impact assessments.
Final-revised paper