Substituent effects on the disproportionation—combination rate constant ratios for gas-phase halocarbon radicals, Part 5: Reactions of CF3 + CF3CH2CHCH3 and CF3CH2CHCH3 + CF3CH2CHCH3

✍ Scribed by John D. Ferguson; Bert E. Holmes

• Publisher: John Wiley and Sons
• Year: 2001
• Tongue: English
• Weight: 184 KB
• Volume: 33
• Category: Article
• ISSN: 0538-8066
• DOI: 10.1002/kin.1050

✦ Synopsis

Abstract

Rate constant ratios, k~d~/k~c~ for the disproportionation/combination reaction have been measured as 0.07 ± 0.02 when an H is removed from the CH~2~ position of the CF~3~CH~2~CHCH~3~ radical and as 0.24 ± 0.03 when the H is removed from the CH~3~ position in the reaction with the CF~3~ radical. For the self‐reaction between two CF~3~CH~2~CHCH~3~ radicals, k~d~/k~c~ has been measured as 0.27 ± 0.03 when the H is removed from the CH~2~ position and as 0.47 ± 0.04 when the H is removed from the CH~3~ position. The branching fraction, corrected for the number of hydrogens at each site, is 0.70 favoring the methyl position when the acceptor radical is CF~3~ and 0.54 when CF~3~CH~2~CHCH~3~ is the acceptor radical. Branching fraction results show that the CF~3~ substituent on the CF~3~CH~2~CHCH~3~ radical hinders disproportionation when CF~3~ is the acceptor radical. When the accepting radical is CF~3~CH~2~CHCH~3~ the CF~3~ substituent may slightly impede the disproportionation reaction, but the branching ratio is nearly statistical. The effect of substituents on the donor radical, CF~3~CH~2~CHX, will be discussed for the series X = H, CF~3~, Cl, and CH~3~ when the acceptor radical is CF~3~. © 2001 John Wiley & Sons, Inc. Int J Chem Kinet 33: 549–557, 2001