Gas phase production and loss of isoprene epoxydiols.
Isoprene epoxydiols (IEPOX) form in high yields from the OH-initiated oxidation of isoprene under low-NO conditions. These compounds contribute significantly to secondary organic aerosol formation. Their gas-phase chemistry has, however, remained largely unexplored. In this study, we characterize the formation of IEPOX isomers from the oxidation of isoprene by OH. We find that cis-β- and trans-β-IEPOX are the dominant isomers produced, and that they are created in an approximate ratio of 1:2 from the low-NO oxidation of isoprene. Three isomers of IEPOX, including cis-β- and trans-β, were synthesized and oxidized by OH in environmental chambers under high- and low-NO conditions. We find that IEPOX reacts with OH at 299 K with rate coefficients of (0.84 ± 0.07) × 10(-11), (1.52 ± 0.07) × 10(-11), and (0.98 ± 0.05) × 10(-11) cm(3) molecule(-1) s(-1) for the δ1, cis-β, and trans-β isomers. Finally, yields of the first-generation products of IEPOX + OH oxidation were measured, and a new mechanism of IEPOX oxidation is proposed here to account for the observed products. The substantial yield of glyoxal and methylglyoxal from IEPOX oxidation may help explain elevated levels of those compounds observed in low-NO environments with high isoprene emissions.
Division of Chemistry and Chemical Engineering, California Institute of Technology , 1200 East California Boulevard, Pasadena, California 91125, United States.
Kelvin H
KH
Bates
John D
JD
Crounse
Jason M
JM
St Clair
Nathan B
NB
Bennett
Tran B
TB
Nguyen
John H
JH
Seinfeld
Brian M
BM
Stoltz
Paul O
PO
Wennberg
D000475:Alkenes / Q000737:chemistry; D002070:Butadienes / Q000737:chemistry*; D002072:Butylene Glycols / Q000138:chemical synthesis / Q000737:chemistry*; D002849:Chromatography, Gas; D005740:Gases / Q000737:chemistry*; D045782:Hemiterpenes / Q000737:chemistry*; D006878:Hydroxides / Q000737:chemistry; D007536:Isomerism; D008958:Models, Molecular; D015394:Molecular Structure; D009569:Nitric Oxide / Q000737:chemistry; D010084:Oxidation-Reduction; D010420:Pentanes / Q000737:chemistry*; D019946:Propylene Glycol / Q000138:chemical synthesis / Q000737:chemistry*; D013696:Temperature; D013995:Time
C000592504:2-(oxiran-2-yl)-propane-1,2-diol; D000475:Alkenes; D002070:Butadienes; D002072:Butylene Glycols; D005740:Gases; D045782:Hemiterpenes; D006878:Hydroxides; D010420:Pentanes; C000592503:cis-2-methyl-2,3-epoxy-1,4-butanediol; C005059:isoprene; D009569:Nitric Oxide; D019946:Propylene Glycol; C031356:hydroxide ion; C013658:propylene