RATE CONSTANTS FOR THE REACTIONS OF THE NO3 RADICAL WITH ALKANES AT 296+/-2K

Rate constants for the gas-phase reactions of the NO3 radical with a series of branched and straight-chain alkanes have been measured at 296+/-2 K using a relative rate method. Using a rate constant for the reaction of the NO3 radical with 2,3-dimethylbutane of 4.08 x 10(-16) cm(3) molecule(-1) s(-1) at 296 K, the rate constants obtained (in units of 10(-16) cm(3) molecule(-1) s(-1)) were: 2-methylbutane, 1.56 +/- 0.16; 2-methylpentane, 1.71+/-0.18; 3-methylpentane, 2.04+/-0.21; 2,4-dimethylpentane, 1.44+/-0.45; 2,2,3-trimethylbutane, 2.23+/-0.33; 2,2,4-trimethylpentane, 0.75+/-0.32; 2,2,3,3-tetramethylbutane, <0.49; n-nonane, 1.92+/-0.53; and n-decane, 2.59+/-0.61, where the indicated error limits are two least-squares standard deviations and do not include the estimated overall uncertainties in the rate constant for the reference alkane 2,3-dimethylbutane. While the rate constants for the reactions of the NO3 radical with the n-alkanes n-butane through n-decane increase linearly with the carbon number, the rate constants for several of the branched alkanes show deviations from the expected correlation with the number of tertiary drop CH- groups.