Rate constant for chlorine abstraction from CCl 4 by the 5-hexenyl radical
1987; NRC Research Press; Volume: 65; Issue: 2 Linguagem: Inglês
10.1139/v87-052
ISSN1480-3291
AutoresDeborah Rae Jewell, Lukose Mathew, John Warkentin,
Tópico(s)Atmospheric Ozone and Climate
ResumoCyclization of the 5-hexenyl free radical to the cyclopentylmethyl free radical was used to clock chlorine atom abstraction by 5-hexenyl from carbon tetrachloride in solution. The source of 5-hexenyl radicals was 5-hexenyl[1-hydroxy-1-methyl-ethyl]diazene ((CH 3 ) 2 C(OH)N=N(CH 2 ) 4 CH=CH 2 ), which decomposes thermally in CCl 4 by a radical chain mechanism to afford chloroform, acetone, nitrogen, 6-chloro-1-hexene, cyclopentylchloromethane, 1-hexene, and methylcyclopentane as primary products. 6-Chloro-1-hexene is converted, in part, to a secondary product, 1,1,1,3,7-pentachloroheptane, by radical chain addition of CC1 4 to the double bond. The rate constant for chlorine atom abstraction, k Cl , was calculated from the product composition and the known rate constant for cyclization of the 5-hexenyl radical. For the temperature range 274–353 K, k Cl is given by log (k Cl /M −1 s −1 ) = (8.4 ± 0.3) − (6.2 ± 0.4)/θ where θ = 2.3 RT kcal mol −1 , which leads to [Formula: see text]. This value is significantly smaller than recently reported estimates for other primary alkyl radicals.
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