Gas-Phase Ozonolysis of Cycloalkenes: Formation of Highly Oxidized RO2 Radicals and Their Reactions with NO, NO2, SO2, and Other RO2 Radicals

详细信息    查看全文

• 作者：Torsten Berndt ; Stefanie Richters ; Ralf Kaethner ; Jens Voigtl盲nder ; Frank Stratmann ; Mikko Sipil盲 ; Markku Kulmala ; Hartmut Herrmann
• 刊名：Journal of Physical Chemistry A
• 出版年：2015
• 出版时间：October 15, 2015
• 年：2015
• 卷：119
• 期：41
• 页码：10336-10348
• 全文大小：640K
• ISSN：1520-5215

文摘

The gas-phase reaction of ozone with C₅鈥揅₈ cycloalkenes has been investigated in a free-jet flow system at atmospheric pressure and a temperature of 297 卤 1 K. Highly oxidized RO₂ radicals bearing at least 5 O atoms in the molecule and their subsequent reaction products were detected in most cases by means of nitrate-CI-APi-TOF mass spectrometry. Starting from a Criegee intermediate after splitting-off an OH-radical, the formation of these RO₂ radicals can be explained via an autoxidation mechanism, meaning RO₂ isomerization (ROO 鈫?QOOH) and subsequently O₂ addition (QOOH + O₂ 鈫?R鈥睴O). Time-dependent RO₂ radical measurements concerning the ozonolysis of cyclohexene indicate rate coefficients of the intramolecular H-shifts, ROO 鈫?QOOH, higher than 1 s^鈥?. The total molar yield of highly oxidized products (predominantly RO₂ radicals) from C₅鈥揅₈ cycloalkenes in air is 4.8鈥?.0% affected with a calibration uncertainty by a factor of about two. For the most abundant RO₂ radical from cyclohexene ozonolysis, O,O鈥揅₆H₇(OOH)₂O₂ (鈥淥,O鈥?stands for two O atoms arising from the ozone attack), the determination of the rate coefficients of the reaction with NO₂, NO, and SO₂ yielded (1.6 卤 0.5) 脳 10^鈥?2, (3.4 卤 0.9) 脳 10^鈥?1, and <10^鈥?4 cm³ molecule^鈥? s^鈥?, respectively. The reaction of highly oxidized RO₂ radicals with other peroxy radicals (R鈥睴₂) leads to detectable accretion products, RO₂ + R鈥睴₂ 鈫?ROOR鈥?+ O₂, which allows to acquire information on peroxy radicals not directly measurable with the nitrate ionization technique applied here. Additional experiments using acetate as the charger ion confirm conclusively the existence of highly oxidized RO₂ radicals and closed-shell products. Other reaction products, detectable with this ionization technique, give a deeper insight in the reaction mechanism of cyclohexene ozonolysis.