Primary product distribution from the Cl-atom initiated atmospheric degradation of furan: Environmental implications

Furan is an aromatic hydrocarbon present in both urban and rural atmospheres, which is emitted mainly by biomass burning and the combustion of fossil fuel. Reaction of furan and Cl atoms may be important in areas where chlorine atom concentrations are potentially high such as marine and coastal regions or continental atmospheres where industrial activity emits molecular chlorine or photo-labile Cl-containing compounds. To assess the importance of this reaction and to investigate whether any unique chlorine-containing product is formed the products of the reaction of Cl atoms with furan have been determined under atmospheric conditions. For the study two different sampling/detection methods have been used: (1) Solid-Phase MicroExtraction, with subsequent analysis by thermal desorption, and gas chromatography with mass spectrometry or flame ionization detection (SPME/GC-MS/FID), and 2-“in situ” with long path fourier transform infrared spectroscopy (FTIR). The yields of primary reaction products in the absence of NO were: 5-chloro-2(5H)-furanone (64.5±10.7)%, E-butenedial (11±3)%, 5-hydroxy-2(5H)-furanone ( 2.4%) and Z-butenedial (1.6±0.5)%. Other products generated by secondary reactions were 2(3H)-furanone (2.8±1.9)%, HCl (21.1±3%) and CO. Maleic anhydride was detected with a yield of about 2%, however, this yield may be a combination of both primary and secondary reactions. All errors are ±2σ. The observed products confirm that addition of Cl atoms to the double bond of furan is the dominant reaction pathway.