Rate Coefficients for the Reactions of OH Radicals with a Series of Alkyl-Substituted Amines.

Abstract

Rate coefficients have been determined at (298 ± 2) K and atmospheric pressure for the reaction of OH radicals with two primary monoalkyl-, one secondary dialkyl-, and five tertiary trialkyl-substituted amines in a large volume photoreactor by the relative kinetic technique. The following rate coefficients (in cm3 molecule-1 s-1 units) have been obtained: (1) 1,2-dimethylpropylamine, CH3C(CH3)HC(CH3)H)NH2, (5.08 ± 1.02) × 10-11; (2) tert-amylamine (tert-pentylamine), CH3CH2C(CH3)2NH2, (0.86 ± 0.17) × 10-11; (3) diethylamine, (CH3CH2)2NH, (7.36 ± 1.47) × 10-11; (4) N,N-dimethylethylamine, (CH3)2NCH2CH3, (7.37 ± 1.47) × 10-11; (5) N,N-dimethylpropylamine, (CH3)2NCH2CH2CH3, (10.97 ± 1.78) × 10-11; (6) N,N-dimethylisopropylamine, (CH3)2NCH(CH3)2, (9.79 ± 1.75) × 10-11; (7) N,N-diethylmethylamine, (CH3CH2)2NCH3, (8.92 ± 1.54) × 10-11; (8) triethylamine, (CH3CH2)3N, (10.86 ± 1.88) × 10-11. The quoted errors are the 2σ deviations from least-squares linear analysis of the kinetic data plus a contribution to take into account uncertainties associated with the reference compounds. With the exception of diethylamine, this study represents the first determinations of the rate coefficients for reaction of the compounds with OH radicals. The results are compared with rate coefficients available in the literature for smaller alkyl-substituted amines and also the values predicted for the compounds investigated by using a structure activity relationship (SAR). With the exception of tert-amylamine, the SAR-predicted OH rate coefficients are in good agreement with the experimental values.