Kinetics Studies of the Gas-Phase Reactions of NO 3 Radicals with Series of 1-Alkenes, Dienes, Cycloalkenes, Alkenols, and Alkenals
. The Journal of Physical Chemistry A 2011
The gas-phase reactions of NO3 radicals with series of 1-alkenes, dienes, cycloalkenes, alkenols, and alkenals were studied in pure N2 or 20% O2/80% N2 bath gas at room temperature and atmospheric pressure using a relative rates technique. Rate coefficients were derived from rates of loss of the organic compounds observed using a chemical ionization mass spectrometer. No difference in the measured kinetic data was observed in the presence or absence of O2. The rate coefficients obtained (k (10–13 cm3 molecule–1 s–1), with uncertainties representing 95% confidence intervals) are as follows: 1-hexene, 0.233 ± 0.021; 1-heptene, 0.245 ± 0.029; 1-octene, 0.292 ± 0.044; 1,3-butadiene, 1.24 ± 0.09; isoprene, 6.24 ± 0.11; 2,3-dimethyl-1,3-butadiene, 14.1 ± 0.5; 1,3-cyclohexadiene, 112 ± 8; cyclopentene, 4.82 ± 0.13; cyclohexene, 5.38 ± 0.20; cycloheptene, 5.28 ± 0.23; 2-buten-1-ol (crotyl alcohol), 3.23 ± 0.12; cis-2-penten-1-ol, 3.11 ± 0.11; cis-2-hexen-1-ol, 3.81 ± 0.38; trans-2-pentenal, 0.193 ± 0.040; trans-2-hexenal, 0.136 ± 0.029; trans-2-heptenal, 0.231 ± 0.036; cis-4-heptenal, 4.03 ± 0.24. The measured rate coefficients are compared to values from previous studies and three structure–activity relationships (SARs), and good agreement is found, in general. In particular, the recently developed SAR of Kerdouci et al. (Kerdouci, J.; Picquet-Varrault, B.; Doussin, J. ChemPhysChem2010, 11, 3909–3920.) is found to estimate the rate coefficients within 35% for all of the measured reactions except for NO3 + 1,3-butadiene. The SAR prediction for that reaction is nearly 50% lower than the measured value, suggesting that it underestimates the effect of conjugation on the reaction of NO3 with this small diene. The measured rate coefficients for reactions with a series of alkenols are used to modify the SAR substituent factor for the −CH2OH group, and those for reactions with a series of trans-2-alkenals are used to derive a substituent factor for the −C(O)H group, which was not included in the original SAR because of insufficient experimental data.