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Using a relative kinetic technique, rate coefficients have been determined at (298 ± 2) K and atmospheric pressure for the gas-phase reactions of the NO3 radical with three vicinal dihydroxy aromatic compounds. The experiments were carried out in a 1080-l quartz glass reactor at the Bergische Universitat Wuppertal and in the European Photoreactor (EUPHORE), Valencia, Spain. The rate coefficients obtained (in units of cm3 molecule−1 s−1) using 2,3-dimethyl-2-butene as the reference hydrocarbon were kNO3(1,2-dihydroxybenzene) = (9.8 ± 5.0) × 10−11, kNO3(1,2-dihydroxy-3-methylbenzene) = (17.2 ± 5.6) × 10−11, and kNO3 (1,2- dihydroxy-4-methylbenzene) = (14.7 ± 6.5) × 10−11. This study represents the first kinetic investigation of the reactions of the NO3 radical with dihydroxybenzenes. © 2004 Wiley Periodicals, Inc. Int J Chem Kinet 36: 577–583, 2004

The rate constant for the reaction of OH radicals with pinonaldehyde has been measured at 293 6 6 K using the relative rate method in the laboratory in Wuppertal (Germany) using photolytic sources for the production of OH radicals and in the EUPHORE smog chamber facility in Valencia (Spain) using the in situ ozonolysis of 2,3-dimethyl-2-butene as a dark source of OH radicals. In all the experiments pinonaldehyde and the reference compounds were monitored by FTIR spectroscopy, and in addition in the EUPHORE smog chamber the decay of pinonaldehyde was monitored by the HPLC/DNPH method and the reference com- pound by GC/FID. The results from all the different series of experiments were in good agree- ment and lead to an average value of k(pinonaldehyde 1 OH) 5 (4.0 6 1.0) 3 10 211 cm 3 molecule 21 s 21 . This result lead to steady-state estimates of atmospheric pinonaldehyde con- centrations in the ppbV range (1 ppbV < 2.5 3 10 10 molecule cm 23 at 298 K and 1 atm) in regions with substantial a-pinene emission. It also implies that atmospheric sinks of pinon- aldehyde by reaction with OH radicals could be half as important as its photolysis. The rate constant of the reaction of pinonaldehyde with Cl atoms has been measured for the first time. Relative rate measurements lead to a value of k(pinonaldehyde 1 Cl) 5 (2.4 6 1.4) 3 10210 cm3 molecule21 s21. In contrast to previous studies which suggested enhanced kinetic reactivity for pinonaldehyde compared to other aldehydes, the results from both the OH- and Cl-initiated oxidation of pinonaldehyde in the present work are in line with predic- tions using structure-activity relationships. q 1999 John Wiley & Sons, Inc., Int J Chem Kinet 31: 291- 301, 1999