The Hydroxyl Radical Reaction Rate Constant and Products of Dimethyl Succinate

The relative rate technique has been used to examine the kinetics for the reaction of the hydroxyl radical OH with dimethyl succinate DMS, CH3OCOCH2CH2COOCH3. The measured rate constant for OH DMS was 1.5 - 0.4 x 10exp -12 ccmolecules at 297 - 3 deg K and 1 atmosphere total pressure. This is in agreement with the predicted value of 1.15 x 10exp -12 ccmolecules determined by structure activity relationships. To more clearly define DMSs atmospheric degradation mechanism, the products of the OH DMS reaction were also investigated. The only primary product detected was mono methyl succinate MMS, CH3OCOCH2CH2COOH at a yield of only 2.17 - 0.25. Extensive efforts were used to identify other primary products but none were measured. Formic acid HCOOH however, was observed as a secondary product being formed at a rate of 4.6 - 1.3 x 10exp 14 moleculessecond, 60 minutes after initiating the OH DMS reaction. Formic acid is believed to be a degradation product of the primary product, methyl glyoxylate MG, CH3OCOCOH. Product formation pathways are discussed in light of current understanding of the atmospheric chemistry of oxygenated organic compounds.