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Rate constants for the gas-phase reactions of OH radical, NO 3 radical, and ozone with allyl alcohol (AAL) and allyl isocyanate (AIC) have been measured using relative rate methods at atmospheric pressure in purified air. The experimental Arrhenius expression obtained for the reaction of the OH radical with AAL is (1.68 ( 0.89) × 10 -12 × exp(1100/T) cm 3 molecule -1 s -1 , for T ) 282-315 K; the Arrhenius expression for the reaction of OH radical with AIC is (1.94 ( 1.04) × 10 -14 × exp(2207/T) cm 3 molecule -1 s -1 , for T ) 282-317 K, where the indicated errors are one least-squares standard deviation. All OH radical reaction rate constants have been measured relative to k(OH + R-pinene) and k(OH + 1,3,5-trimethylbenzene). The rate constant for the gas-phase reaction of OH radical with allyl alcohol-d 6 isotopomer (AAL-d 6 ) has been measured at T ) 298 K, and the value is 5.10 × 10 -11 cm 3 molecule -1 s -1 . The kinetic isotope effect is small, with k(AAL)/k(AAL-d 6 ) ) 1.32. Rate constants for the gas-phase reactions of NO 3 radical with AAL [relative to k(NO 3 +methacrolein)] and O 3 [relative to k(O 3 + β-pinene)] have been measured, and the values are 7.7 × 10 -15 cm 3 molecule -1 s -1 at T ) 298 K and 1.6 × 10 -17 cm 3 molecule -1 s -1 at T ) 296 K, respectively. Rate constants for the gas-phase reactions of NO 3 radical and O 3 with AIC have been measured, and the values are 9.4 × 10 -16 cm 3 molecule -1 s -1 at T ) 299 K and 5.54 × 10 -18 cm 3 molecule -1 s -1 at T ) 299 K, respectively. Multireference ab initio calculations at the MRMP2/6-311G(d,p) level have been carried out for reactions of OH radical with AAL and AIC. Results indicate that prereactive hydrogen bonded complexes form in the entrance channels for these reactions.

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The rate constant for the gas-phase reaction of hydroxyl radical with isopropyl isocyanate (IIC) has been measured, relative to toluene, in the T = 287-321 K range at atmospheric pressure in air. Ultraviolet photolysis of methyl nitrite served as the source of hydroxyl radical. The experimental Arrhenius expression obtained for this reaction is 7.09 × 10 −13 × exp[(307 ± 263)/T ] cm 3 molecule −1 s −1 , where the indicated error is one leastsquares standard deviation and does not include the uncertainty in the rate constant for toluene. Multilevel ab initio calculations, performed at the MP-SAC2 level, indicate that hydrogen atom transfer from the tertiary carbon atom occurs without an energy barrier, in agreement with the experimentally observed slight negative temperature dependence of the rate constant. The calculations indicate that hydrogen-bonded complexes of IIC and OH form in the reactant entrance channels along the minimum-energy paths. Use of conventional transition state theory and MP-SAC2 scaled transition state relative energies, with an asymmetric Eckart tunneling model for transfer of a hydrogen atom from a methyl group, yields a theoretical rate constant of 1.81 × 10 −18 × T 2 × exp(744/T ) cm 3 molecule −1 s −1 in the T = 200-350 K range. From the rate constant data, an estimated upper limit for the tropospheric lifetime of IIC is determined as 6.0 days at 15 • C, based on the global weighted-average OH concentration of 9.4 × 10 5 molecules cm −3 determined by Prinn et al.