Atmospheric chemistry of camphor

Rate constants have been measured at 296 +/- 2 K for the gas-phase reaction s of camphor with OH radicals. NO3 radicals, and O-3. Using relative rate m ethods, the rate constants for the OH radical and NO3 radical reactions wer e (4.6 +/- 1.2) X 10(-12) cm(3) molecule(-1) s(-1) and <3 x 10(-16) cm(3) m olecule(-1) s(-1). respectively. where the indicated error in the OH radica l reaction rate constant includes the estimated overall uncertainty in the rate constant for the reference compound. An upper limit to the rate consta nt for the O-3 reaction of <7 X 10(-20) cm(3) molecule(-1) s(-1) was also d etermined. The dominant tropospheric loss process for camphor is calculated to be by reaction with the OH radical. Acetone was identified and quantifi ed as a product of the OH radical reaction by gas chromatography, with a fo rmation yield of 0.29 +/- 0.04. In situ atmospheric pressure ionization tan dem mass spectrometry (API MSI analyses indicated the formation of addition al products of molecular weight 166 (dicarbonyl), 182 (hydroxydicarbonyl). 186. 187, 213 (carbonyl-nitrate), 229 (hydroxycarbonyl-nitrate), and 243. A reaction mechanism leading to the formation of acetone is presented, as ar e pathways for the formation of several of the additional products observed by API-MS. (C) 2000 John Wiley and Sons. Inc.