Bethel H L, Arey J, Atkinson R
Air Pollution Research Center, Interdepartmental Graduate Program in Environmental Toxicology, University of California, Riverside 92521, USA.
Environ Sci Technol. 2001 Nov 15;35(22):4477-80. doi: 10.1021/es010808z.
3-Hexene-2,5-dione [CH3C(O)CH=CHC(O)CH3] and other unsaturated 1,4-dicarbonyls are formed from the atmospheric photooxidations of aromatic hydrocarbons. We have investigated the products of the gas-phase reaction of OH radicals with 3-hexene-2,5-dione in the presence of NO at room temperature and atmospheric pressure of air using in situ atmospheric pressure ionization tandem mass spectrometry. Products of molecular weight 102 and 191 were identified and from consideration of the potential reactions these are attributed to CH3C(O)CH(OH)CHO and CH3C(O)CH(OH)CH(ONO2)C(O)CH3, respectively. After initial addition of the OH radical, the CH3C(O)CH(OH)(*C)HC(O)CH3 radical adds O2 to form the peroxy radical which reacts with NO to yield the molecular weight 191 hydroxynitrate CH3C(O)CH(OH)CH(ONO2)C(O)CH3 or the hydroxyalkoxy radical CH3C(O)CH(OH)CH(*O)C(O)CH3 plus NO2. Our observation of a molecular weight 102 species indicates that the CH3C(O)CH(OH)CH(*O)C(O)CH3 radical dominantly decomposes to CH3C(O)CH(OH)CHO plus CH3(*C)O, rather than decomposing to CH3C(O)CHO plus CH3C(O)(*C)HOH, isomerizing, or reacting with O2. Thermochemical calculations and an empirical estimation method for calculating alkoxy radical reaction rates are consistent with our experimental observations.
3-己烯-2,5-二酮[CH3C(O)CH=CHC(O)CH3]和其他不饱和1,4-二羰基化合物是由芳烃的大气光氧化反应形成的。我们利用原位大气压电离串联质谱，在室温和空气大气压条件下，研究了在NO存在下OH自由基与3-己烯-2,5-二酮的气相反应产物。鉴定出了分子量为102和191的产物，考虑到可能的反应，它们分别归因于CH3C(O)CH(OH)CHO和CH3C(O)CH(OH)CH(ONO2)C(O)CH3。在OH自由基最初加成后，CH3C(O)CH(OH)(*C)HC(O)CH3自由基与O2反应形成过氧自由基，该过氧自由基与NO反应生成分子量为191的羟基硝酸盐CH3C(O)CH(OH)CH(ONO2)C(O)CH3或羟基烷氧基自由基CH3C(O)CH(OH)CH(*O)C(O)CH3加NO2。我们对分子量为102的物质的观察表明，CH3C(O)CH(OH)CH(*O)C(O)CH3自由基主要分解为CH3C(O)CH(OH)CHO加CH3(*C)O，而不是分解为CH3C(O)CHO加CH3C(O)(*C)HOH、异构化或与O2反应。热化学计算和计算烷氧基自由基反应速率的经验估计方法与我们的实验观察结果一致。
