Kinetics of the Reactions of OH Radicals with 2- and 3-Methylfuran, 2,3- and 2,5-Dimethylfuran, and E- and Z-3-Hexene-2,5-dione, and Products of OH + 2,5-Dimethylfuran

摘要

Furan and alkylfurans are present in the atmosphere from direct emissions and in situ formation from other volatile organic compounds. The OH radical-initiated reactions of furan and alkyifurans have been proposed as relatively clean in situ sources of unsaturated 1,4-dicarbonyls, some of which are otherwise not readily available. Using a relative rate method, rate constants at 296 ± 2 K for the gas-phase reactions of OH radicals with 2- and 3-methvlniran, 2,3- and 2,5-dimethyliuran, and Z- and E-3-hexene-2,5-dione have been measured, of (in units of 10~(-11) cm~3 molecule~(-1) s~(-1) ): 2-methylfuran, 7.31 ±0.3S; 3-methyIfuran, 8.73 ±0.18; 2,3-dimethylmran, 12.6 ± 0.4; 2,5-dimethyifuran, 12.5 ± 0.4; Z-3-heiene-2,5-dione, S.90 ± 0.57; and E-3-hexene-2,5-dione, 4.14 ± 0.02. Products of the OH radical-initiated reaction of 2,5-dimethyUuran were investigated, with 3-hexene-2,5-dione being formed with molar yields of 24 ± 3% in the presence of NO and 34 ± 3% in the absence of NO. Direct air sampling atmospheric pressure iomzation mass spectrometry showed the formation of additional products of molecular weight 114, attributed to CH_3C(O)CH=CHC(O)OH and/or S-hydroxy-S-methyl.2-ruranone, and 128, attributed to CH_3C(O)OC(CH_3)=CHCHO.