[1] It is known that isoprene nitrate production can represent a significant sink for atmospheric NO x and free radicals, and therefore this chemistry is important to understanding tropospheric O 3 and the fate of NO x in forest-impacted environments. Although six structural isoprene nitrate isomers can be produced from OH reaction with isoprene in the presence of NO, these have not been separately quantified in the atmosphere. A zero-dimensional isoprene photochemistry model was developed based on the known gas-phase isoprene oxidation chemistry for comparison with isoprene nitrate ambient concentration data obtained from field and laboratory measurements. The model incorporates calculated individual branching ratios for each isomer as well as rate constants for the reaction of each isomeric nitrate with the OH radical and O 3 and losses from the boundary layer by dry deposition and vertical mixing. The model indicates that under atmospheric conditions, there should be three nitrate isomers that represent 86% of the total, while our ambient measurements indicate only two dominant nitrate isomers. This contrasts significantly with what is observed in the laboratory because of atmospheric conversion to other nitrogen-containing products. These secondary nitrates are likely to be a significant fraction of NO y in forest environments.Citation: Giacopelli, P., K. Ford, C. Espada, and P. B. Shepson (2005), Comparison of the measured and simulated isoprene nitrate distributions above a forest canopy,

Production of organic nitrates from OH reaction with cyclohexane, cyclohexene, n-butane, 1-bromopropane, and p-xylene in the presence of NO was studied. The total organic nitrate yields for cyclohexane and n-butane were determined to be 17 ± 4 and 7 ± 2% respectively, which is in good agreement with previous determinations. Total yields for cyclohexene, 1-bromopropane, and p-xylene were 2.5 ± 0.5, 1.2 ± 0.3, and 3.2 ± 0.7 respectively. The yield for cyclohexene was five times smaller than that for cyclohexane. The 1-bromopropane yield is three times smaller that that for n-propane, but similar to that for propene, indicating that the effect of Br substitution in the reactant may be similar to that for OH substitution. The only nitrooxy product detected for p-xylene was 4-methylbenzylnitrate, which was formed following H abstraction from either methyl group. No organic nitrate was detected for peroxy radicals produced from OH addition to the ring, which accounts for 90% of the OH oxidation of p-xylene. The calculated k 3b /k 3 value for p-methyl benzyl peroxy radicals (0.32) was slightly smaller than for n-octyl peroxy radicals (0.39). These data imply that substituent inductive effects impact the k 3b /k 3 ratios. We found no significant difference in the k 3b /k 3 ratios for primary vs. secondary peroxy radicals of the same carbon chain. C 2005 Wiley Periodicals, Inc. Int J Chem Kinet 37: [675][676][677][678][679][680][681][682][683][684][685] 2005

The production of organic nitrates from OH reaction (in the presence of NO) with methoxy propane, 1-methoxy-2-propanol, ethoxy butane, and 2-butoxyethanol was studied. The measured total organic nitrate yields were 1.8 (±0.4)%, 0.98 (±0.2)%, 7.7 (±2)%, and 9.6 (±1)%, respectively. The total organic nitrate yield for methoxypropane is 26% of that (7.0%) for n-butane. The organic nitrate yield for ethoxy butane is 55% of that (14%) for n-hexane. The peroxy radicals produced from OH reaction with the methylene groups α to the ether linkage have an organic nitrate branching ratio (k 3b /k 3 ) value ∼50% of those in analogous n-alkanes. On the other hand, k 3b /k 3 values for peroxy radical functional groups not adjacent to the ether linkage (in γ and δ positions) are on average 1.7 times greater than for the analogous n-alkyl peroxy radicals. The organic nitrate formation yield for 1-methoxy-2-propanol is almost half that of methoxy propane, while for 2-butoxyethanol it is 21% greater than that of butoxyethane. Our data lead us to the conclusion that the ether linkage imparts an inductive effect that decreases the value of k 3b /k 3 for peroxy radicals adjacent to it, yet has a stabilizing effect, from the additional vibrational modes for those peroxy radicals not adjacent to it, increasing their k 3b /k 3 values. The effect of both the O and OH groups in these molecules and the importance of their position relative to the peroxy group are discussed in this paper. C

Ammonia is the primary attractant for tephritid fruit flies, and traps baited with synthetic attractants using ammonia formulations have been highly successful in capturing these pests. However, difficulties in quantifying release rates of ammonia have limited abilities to make comparisons among field tests of different species by using different formulations. Therefore, Fourier transform infrared (FTIR) spectroscopy was evaluated as a method to quantify ammonia from synthetic lures. Analysis of the headspace from commercial ammonium bicarbonate and ammonium acetate lures indicated that there is a large burst of ammonia liberated upon initial exposure of the lures, but after 5-7 d the release rates stabilize and remain steady for at least 60 d under laboratory conditions. During the period of steady release, FTIR st atic measurements showed a n average of 0.12 and 0.21 microg of ammonia per 50-ml sample from ammonium bicarbonate and ammonium acetate lures, respectively. FTIR dynamic measurements from ammonium acetate lures indicated a steady release rate of approximately 200 microg/h. Ammonia release rate from ammonium acetate lures could be reduced by decreasing the surface area of the release membrane, and the presence of crystal formations on the membrane seemed to decrease the longevity of the ammonium acetate lures.