Temperature‐dependent rate coefficient measurements for the reaction of bromine atoms with a series of aldehydes

Relative rate coefficient data have been obtained for the reactions Br + RCHO → RCO + HBr for a series of aldehydes: HCHO, reaction (1); CH₃CHO, reaction (2); CH₃CH₂CHO, reaction (3); CH₃CH₂CH₂CHO, reaction (4). Measurements were made over the temperature range 240–300 K in an environmental chamber/FTIR spectrometer system, using standard relative rate techniques. All measured rate coefficient ratios were found to be independent of temperature over the range studied (k₂/k₁ = 3.60 ± 0.29, k₃/k₁ = 6.65 ± 0.53, k₄/k₁ = 8.62 ± 0.69, and k₃/k₂ = 1.80 ± 0.14), implying that the activation barriers for all four reactions are essentially identical with the A‐factors increasing with the size of the aldehyde. Relative rate coefficients for k₁ and k₂ agree well with currently recommended data at room temperature, but inconsistencies on the order of 20% arise at lower temperatures. The entire set of relative rate coefficient measurements is put on an absolute scale using a combination of currently recommended values for k₁ and k₂. The following expressions (all in units of cm³ molecule^?1 s^?1) are obtained: k₁ = (0.79 ± 0.10) × 10^?11 exp(?580 ± 200/T), k₂ = (2.7 ± 0.4) × 10^?11 exp(?567 ± 200/T), k₃ = (5.75 ± 0.75) × 10^?11 exp(?610 ± 200/T), k₄ = (5.75 ± 0.75) × 10^?11 exp(?540 ± 200/T), where uncertainties quoted for the A‐factor reflect the uncertainty in the room temperature value. © 2000 John Wiley & Sons, Inc. Int J Chem Kinet 32: 460–465, 2000