The Hydroxyl Radical Reaction Rate Constant and Products of Dimethyl Succinate

Abstract

Abstract : The relative rate technique has been used to examine the kinetics for the reaction of the hydroxyl radical (OH) with dimethyl succinate (DMS, CH3OC(=O)CH2CH2C(=O)OCH3). The measured rate constant for OH + DMS was 1.5 +/- 0.4 x 10(exp -12) cc/molecule/s at 297 +/- 3 deg K and 1 atmosphere total pressure. This is in agreement with the predicted value of 1.15 x 10(exp -12) cc/molecule/s determined by structure activity relationships. To more clearly define DMS's atmospheric degradation mechanism, the products of the OH + DMS reaction were also investigated. The only primary product detected was mono methyl succinate (MMS, CH3OC(=O)CH2CH2C(=O)OH)) at a yield of only 2.17 +/- 0.25%. Extensive efforts were used to identify other primary products but none were measured. Formic acid (HC(=O)OH ); however, was observed as a secondary product being formed at a rate of (4.6 +/- 1.3) x 10(exp 14) molecules/second, 60 minutes after initiating the OH + DMS reaction. Formic acid is believed to be a degradation product of the primary product, methyl glyoxylate (MG, CH3OC(=O)C(=O)H). Product formation pathways are discussed in light of current understanding of the atmospheric chemistry of oxygenated organic compounds.