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Kinetics and mechanisms of the reactions of chlorine atoms with ethane, propane, and n ‐butane
Author(s) -
Tyndall G. S.,
Orlando J. J.,
Wallington T. J.,
Dill M.,
Kaiser E. W.
Publication year - 1997
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/(sici)1097-4601(1997)29:1<43::aid-kin6>3.0.co;2-l
Subject(s) - chemistry , radical , propane , flash photolysis , diluent , butane , reaction rate constant , torr , hydrogen atom abstraction , photodissociation , chlorine atom , reaction rate , photochemistry , kinetics , analytical chemistry (journal) , medicinal chemistry , organic chemistry , thermodynamics , physics , quantum mechanics , catalysis
Absolute (flash photolysis) and relative (FTIR‐smog chamber and GC) rate techniques were used to study the gas‐phase reactions of Cl atoms with C 2 H 6 ( k 1 ), C 3 H 8 ( k 3 ), and n ‐C 4 H 10 ( k 2 ). At 297 ± 1 K the results from the two relative rate techniques can be combined to give k 2 / k 1 = (3.76 ± 0.20) and k 3 /k 1 = (2.42 ± 0.10). Experiments performed at 298–540 K give k 2 / k 1 = (2.0 ± 0.1)exp((183 ± 20)/T). At 296 K the reaction of Cl atoms with C 3 H 8 produces yields of 43 ± 3% 1‐propyl and 57 ± 3% 2‐propyl radicals, while the reaction of Cl atoms with n ‐C 4 H 10 produces 29 ± 2% 1‐butyl and 71 ± 2% 2‐butyl radicals. At 298 K and 10–700 torr of N 2 diluent, 1‐ and 2‐butyl radicals were found to react with Cl 2 with rate coefficients which are 3.1 ± 0.2 and 2.8 ± 0.1 times greater than the corresponding reactions with O 2 . A flash‐photolysis technique was used to measure k 1 = (5.75 ± 0.45) × 10 −11 and k 2 = (2.15 ± 0.15) × 10 −10 cm 3 molecule −1 s −1 at 298 K, giving a rate coefficient ratio k 2 / k 1 = 3.74 ± 0.40, in excellent agreement with the relative rate studies. The present results are used to put other, relative rate measurements of the reactions of chlorine atoms with alkanes on an absolute basis. It is found that the rate of hydrogen abstraction from a methyl group is not influenced by neighboring groups. The results are used to refine empirical approaches to predicting the reactivity of Cl atoms towards hydrocarbons. Finally, relative rate methods were used to measure rate coefficients at 298 K for the reaction of Cl atoms with 1‐ and 2‐chloropropane and 1‐ and 2‐chlorobutane of (4.8 ± 0.3) × 10 −11 , (2.0 ± 0.1) × 10 −10 , (1.1 ± 0.2) × 10 −10 , and (7.0 ± 0.8) × 10 −11 cm 3 molecule −1 s −1 , respectively. © 1997 John Wiley & Sons, Inc. Int J Chem Kinet 29: 43–55, 1997.