Kinetics of the reactions of OH radicals with 2‐methoxy‐6‐(trifluoromethyl)pyridine,diethylamine, and 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol at 298 ± 2 K

Rate constants for the reactions of 2‐methoxy‐6‐(trifluoromethyl)pyridine, diethylamine, and 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol with OH radicals have been measured at 298 ± 2 K using a relative rate method. The measured rate constants (cm³ molecule^?1 s^?1) are (1.54 ± 0.21) × 10^?12 for 2‐methoxy‐6‐(trifluoromethyl)pyridine, (1.19 ± 0.25) × 10^?10 for diethylamine, and (1.76 ± 0.38) × 10^?12 for 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol, where the indicated errors are the estimated overall uncertainties including those in the rate constants for the reference compounds. No reaction of 2‐methoxy‐6‐(trifluoromethyl)pyridine with gaseous nitric acid was observed, and an upper limit to the rate constant for the reaction of 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol with O₃ of <7 × 10^{? 20} cm³ molecule^?1 s^?1 was determined. Using a 12‐h average daytime OH radical concentration of 2 × 10⁶ molecule cm^?3, the lifetimes of the volatile organic compounds studied here with respect to reaction with OH radicals are 7.5 days for 2‐methoxy‐6‐(trifluoromethyl)pyridine, 1.2 h for diethylamine, and 6.6 days for 1,1,3,3,3‐pentamethyldisiloxan‐1‐ol. Likely reaction mechanisms are discussed. © 2011 Wiley Periodicals, Inc. Int J Chem Kinet 43: 631–638, 2011     

Rate constants for the gas-phase reactions of O3 with a series of monoterpenes and related compounds at 296 ± 2 K

Rate constants for the gas-phase reactions of O₃ with a series of monoterpenes and related compounds have been determined at 296 ± 2 K and 740 torr total pressure of air or O₂ using a combination of absolute and relative rate techniques. Good agreement between the absolute and relative rate data was observed, and the rate constants obtained (in units of 10^?17 cm³ molecule^?1 s^?1) were: α-pinene, 8.7; β-pinene, 1.5; Δ³-carene, 3.8; 2-carene, 24; sabinene, 8.8; d-limonene, 21; γ-terpinene, 14; terpinolene, 140; α-phellandrene, 190; α-terpinene, 870; myrcene, 49; trans-ocimene, 56; p-cymene, <0.005; and 1,8-cineole, <0.015. While these rate constants for α- and β-pinene and sabinene are in good agreement with recent absolute and relative rate determinations, those for the other monoterpenes are generally lower than the literature data by factors of ca. 2–10. The measured rate constants for the monoterpenes are reasonably consistent with predictions based upon the number and positions of the substituent groups around the 〉C?C〈 bond(s).     

Rate constants for the reactions of the OH radical with the propyl and butyl nitrates and 1-nitrobutane at 298 ± 2 k

Using a relative rate method, rate constants for the gas-phase reactions of the OH radical with 1- and 2-propyl nitrate, 1- and 2-butyl nitrate and 1-nitrobutane have been determined in the presence of one atmosphere of air at 298 ± 2 K. Using rate constants for the reactions of the OH radical with propane and cyclohexane of 1.15 × 10^?12 and 7.49 × 10^?12 cm³ molecule^?1 s^?1, respectively, following rate constants (in units of 10^?12 cm³ molecule^?1 s^?1) were obtained: 1-propyl nitrate, 0.62; 2-propyl nitrate, 0.41; 1-butyl nitrate, 1.78; 2-butyl nitrate, 0.93; and 1-nitrobutane, 1.35. These rate constants are compared and discussed with the literature data.     

Products of the gas-phase OH radical-initiated reactions of 4-methyl-2-pentanone and 2,6-dimethyl-4-heptanone

The gas-phase reactions of the OH radical with 4-methyl-2-pentanone and 2,6-dimethyl-4-heptanone have been investigated in the presence of NO_x. Acetone and 2-methylpropanal were identified and qualified as products of both reactions. The acetone yield from 2,6-dimethyl-4-heptanone increased after addition of NO to reacted mixtures, indicating that acetone is formed through the intermediary of an acyl radical. The acetone and 2-methylopropanal formation yields were determined to be 0.78 ± 0.06 and 0.071 ± 0.011, respectively, from 4-methyl-2-pentanone and 0.68 ± 0.11 and 0.385 ± 0.034, respectively, from 2,6-dimethyl-4-heptanone. The possible reaction mechanisms are discussed and compared with these product data, and it is concluded that the experimental data provide direct evidence for isomerization of the (CH₃)₂CHCH₂C(O)CH₂C(O) (CH₃)₂ alkoxy radical formed from 2,6-dimethyl-4-heptanone. However, the isomerization rates of the alkoxy radicals formed from the ketones depend on whether the H-atom abstracted is on a carbon atom α or β to the >C?O group, with H-atom abstraction from C? H bonds on the β carbon atoms being significantly faster than from C? H bonds on the α carbon atoms. © 1995 John Wiley & Sons, Inc.     

Gas phase reaction of NO2 with alkenes and dialkenes

The kinetics of the gas phase reactions of NO₂ with a series of organics have been studied at 295 ± 2 K. It was observed that only 2,3-dimethyl-2-butene and the conjugated dialkenes studied reacted at observable rates, with rate constants which ranged from 1.5 × 10^?20 cm³ molecule^?1 s^?1 for 2,3-dimethyl-2-butene to 1.3 × 10^?17 cm³ molecule^?1 s^?1 for α-phellandrene. These rate constants are compared with the available literature data and the mechanisms of these reactions are discussed.     

Kinetics of the reactions of O3 and OH radicals with a series of dialkenes and trialkenes at 294 ± 2 K

Rate constants for the gas phase reactions of O₃ and OH radicals with 1,3-cycloheptadiene, 1,3,5-cycloheptatriene, and cis- and trans-1,3,5-hexatriene and also of O₃ with cis-2,trans-4-hexadiene and trans -2,trans -4-hexadiene have been determined at 294 ± 2 K. The rate constants determined for reaction with O₃ were (in cm³ molecule^-1s^?1 units): 1,3-cycloheptadiene, (1.56 ± 0.21) × 10^-16; 1,3,5-cycloheptatriene, (5.39 ± 0.78) × 10^?17; 1,3,5-hexatriene, (2.62 ± 0.34) × 10^?17; cis?2,trans-4-hexadiene, (3.14 ± 0.34) × 10^?16; and trans ?2, trans -4-hexadiene, (3.74 ± 0.61) × 10^?16; with the cis- and trans-1,3,5-hexatriene isomers reacting with essentially identical rate constants. The rate constants determined for reaction with OH radicals were (in cm³ molecule^?1 s^?1 units): 1,3-cycloheptadiene, (1.31 ± 0.04) × 10^?10; 1,3,5-cycloheptatriene, (9.12 × 0.23) × 10^?11; cis-1,3,5-hexatriene, (1.04 ± 0.07) × 10^?10; and trans 1,3,5-hexatriene, (1.04 ± 0.17) × 10^?10. These data, which are the first reported values for these di- and tri-alkenes, are discussed in the context of previously determined O₃ and OH radical rate constants for alkenes and cycloalkenes.     

Rate constants for the gas-phase reactions of alkanes with Cl atoms at 296 ± 2 K

Rate constants for the gas-phase reactions of the Cl atom with a series of alkanes have been determined at 296 ± 2 K using a relative rate method. Using a rate constant for the Cl atom reaction with n-butane of 1.94 × 10^?10 cm³ molecule^?1 s^?1, the rate constants obtained (in units of 10^?11 cm³ molecule^?1 s^?1) were: 2-methylpentane, 25.0 ± 0.8; 3-methylpentane, 24.8 ± 0.6; cyclohexane, 30.8 ± 1.2; cyclohexane-d₁₂, 25.6 ± 0.8; 2,4-dimethylpentane, 25.6 ± 1.2; 2,2,3-trimethylbutane, 17.9 ± 0.7; methylcyclohexane, 34.7 ± 1.2; n-octane, 40.5 ± 1.2; 2,2,4-trimethylpentane, 23.1 ± 0.8; 2,2,3,3-tetramethylbutane, 15.6 ± 0.9; n-nonane, 42.9 ± 1.2; n-decane, 48.7 ± 1.8; and cis-bicyclo[4.4.0]decane, 43.1 ± 0.8, where the indicated errors are two least-squares standard deviations and do not include the uncertainties in the n-butane rate constant. These data have been combined with rate constants obtained previously for ten C₂? C₇ alkanes and this entire data set has been used to develop an estimation method allowing the room temperature rate constants for the reactions of the Cl atom with alkanes to be calculated. © 1995 John Wiley & Sons, Inc.     

Kinetics of the gas phase reaction of Cl atoms with a series of organics at 296 ± 2 K and atmospheric pressure

Using a relative rate technique, rate constants have been determined for the gas phase reactions of Cl atoms with a series of organics at 296 ± 2 K and atmospheric pressure of air. Using a rate constant of 1.97 × 10^?10 cm³ molecule^?1 s^?1 for the reaction of Cl atoms with n-butane, the following rate constants (in units of 10^?11 cm³ molecule^?1 s^?1) were obtained: ethane, 6.38 ± 0.18; propane, 13.4 ± 0.5; isobutane, 13.7 ± 0.2; n-pentane, 25.2 ± 1.2; isopentane, 20.3 ± 0.8; neopentane, 11.0 ± 0.3; n-hexane, 30.3 ± 0.6; cyclohexane, 31.1 ± 1.4; 2,3-dimethylbutane, 20.7 ± 0.6; n-heptane, 34.1 ± 1.2; acetylene, 6.28 ± 0.18; ethene, 10.6 ± 0.3; propene, 24.4 ± 0.8; benzene, 1.5 ± 0.9; and toluene, 5.89 ± 0.36. These data are compared and discussed with the available literature values.     

Rate constants for the gas-phase reactions of OH radicals with a series of bi- and tricycloalkanes at 299 ± 2 K: Effects of ring strain

Relative rate constants for the gas-phase reactions of OH radicals with a series of bi- and tricyclic alkanes have been determined at 299 ± 2 K, using methyl nitrite photolysis in air as a source of OH radicals. Using a rate constant for the reaction of OH radicals with cyclohexane of 7.57 × 10^?12 cm³/molec·s, the rate constants obtained are (× 10¹² cm³/molec·s): bicyclo[2.2.1]heptane, 5.53 ± 0.15; bicyclo[2.2.2]octane, 14.8 ± 1.0; bicyclo[3.3.0]octane, 11.1 ± 0.6; cis-bicyclo[4.3.0]nonane, 17.3 ± 1.3; trans-bicyclo[4.3.0]nonane, 17.8 ± 1.3; cis-bicyclo[4.4.0]decane, 20.1 ± 1.4; trans-bicyclo[4.4.0]decane, 20.6 ± 1.2; tricyclo[5.2.1.0^2,6]decane, 11.4 ± 0.4; and tricyclo[3.3.1.1^3,7]decane, 23.2 ± 2.1. These data show that overall ring strain energies of ?4–5 kcal mol^?1 have no significant effect on the rate constants, but that larger ring strain results in the rate constants being decreased, relative to those expected for the strain-free molecules, by ratios which increase approximately exponentially with the overall ring strain.     

Kinetics of the reactions of O3 and OH radicals with furan and thiophene at 298 ± 2 K

Rate constants for the reactions of O₃ and OH radicals with furan and thiophene have been determined at 298 ± 2 K. The rate constants obtained for the O₃ reactions were (2.42 ± 0.28) × 10^?18 cm³/molec·s for furan and <6 ×10^?20 cm³/molec·s for thiophene. The rate constants for the OH radical reactions, relative to a rate constant for the reaction of OH radicals with n-hexane of (5.70 ± 0.09) × 10^?12 cm³/molec·s, were determined to be (4.01 ± 0.30) × 10^?11 cm³/molec·s for furan and (9.58 ± 0.38) × 10^?12 cm³/molec·s for thiophene. There are to date no reported rate constant data for the reactions of OH radicals with furan and thiophene or for the reaction of O₃ with furan. The data are compared and discussed with respect to those for other alkenes, dialkenes, and heteroatom containing organics.