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Temperature‐dependent rate coefficient measurements for the reaction of bromine atoms with a series of aldehydes
Author(s) -
Ramacher B.,
Orlando J. J.,
Tyndall G. S.
Publication year - 2000
Publication title -
international journal of chemical kinetics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.341
H-Index - 68
eISSN - 1097-4601
pISSN - 0538-8066
DOI - 10.1002/1097-4601(2000)32:8<460::aid-kin2>3.0.co;2-p
Subject(s) - chemistry , analytical chemistry (journal) , reaction rate , bromine , reaction rate constant , atmospheric temperature range , thermodynamics , kinetics , organic chemistry , catalysis , physics , quantum mechanics
Relative rate coefficient data have been obtained for the reactions Br + RCHO → RCO + HBr for a series of aldehydes: HCHO, reaction (1); CH 3 CHO, reaction (2); CH 3 CH 2 CHO, reaction (3); CH 3 CH 2 CH 2 CHO, 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 ( k 2 / k 1 = 3.60 ± 0.29, k 3 / k 1 = 6.65 ± 0.53, k 4 / k 1 = 8.62 ± 0.69, and k 3 / k 2 = 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 k 1 and k 2 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 k 1 and k 2 . The following expressions (all in units of cm 3 molecule −1 s −1 ) are obtained: k 1 = (0.79 ± 0.10) × 10 −11 exp(−580 ± 200/T), k 2 = (2.7 ± 0.4) × 10 −11 exp(−567 ± 200/T), k 3 = (5.75 ± 0.75) × 10 −11 exp(−610 ± 200/T), k 4 = (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