Disproportionation reactions between alkyl and fluoroalkyl radicals. II. Fluoro‐ and trifluoromethyl with ethyl radicals

Abstract

Cross-disproportionation/combination ratios for CFH2 and CF3 with C2H5 radicals have been determined to be A = 0.032 f 0.012 and A = 0.098 f 0.020, respectively, over the temperature range 25-75°C. For the pathway that yields CFH and CzHs, A = 0.020 f 0.005 a t 25°C.

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

“…The donor radical contains a CF 3 group at the ␣-carbon and this electronrich substituent may repel an incoming CF 3 acceptor radical, but not a CF 3 CH 2 CHCH 3 radical that has a greater hydrocarbon-radical character. A similar trend has been observed by Pritchard and coworkers [16][17][18][19][20]. For example, when the donor radical was CHF 2 and the acceptor radical was changed from a perfluoro radical to an alkyl radical, k d /k c , for several acceptor radicals, varied as follows: 0.088 (CF 3 ), 0.072 (n-C 3 F 7 ), 0.07 (CHF 2 ), 0.06 (CH 2 F), 0.35 (CH 3 ), 0.37 (C 2 H 5 ), and 0.30 (n-C 3 H 7 ).…”

“…Pritchard and coworkers [17] also found that hydrocarbon acceptor radicals have much larger k d /k c ratios than perfluorocarbon radicals. As mentioned previously, Pritchard and coworkers [16][17][18][19][20] found that methyl, ethyl, and n-propyl radicals, accepting an H from CHF 2 , all had k d /k c near 0.3, whereas the k d /k c values were between 0.06 and 0.09 when the acceptor radical was a n-C 3 F 7 or a CF 3 radical.…”

The Unimolecular Reactions of CF3CHF2 Studied by Chemical Activation: Assignment of Rate Constants and Threshold Energies to the 1,2-H Atom Transfer, 1,1-HF and 1,2-HF Elimination Reactions, and the Dependence of Threshold Energies on the Number of F-Atom Substituents in the Fluoroethane Molecules

“…The data can be fit to a linear plot with an intercept of 0.066 ± 0.051. In principle the intercept should be the disproportionation-combination ratio ( k d / k c ) for reaction 2, which is reported to be 0.09 ± 0.01. A steady-state analysis of the rate equations shows that the slope of this plot should be equal to k H (1 + k d / k c ) + k d / k c ( k HF ).…”

“…The following reactions summarize the principal chemical reactions in this photolytic system. The combination/ disproportionation ratio for CF 3 + CHF 2 is 0.09, 28 and the small amount of singlet-state :CF 2 will be removed by reaction with trans-2-butene. An asterisk denotes vibrational excitation of CF…”

“…The following reactions summarize the principal chemical reactions in this photolytic system. The combination/disproportionation ratio for CF 3 + CHF 2 is 0.09, and the small amount of singlet-state :CF 2 will be removed by reaction with trans -2-butene. An asterisk denotes vibrational excitation of CF 3 CHF 2 *, and M represents a bath gas molecule (CF 3 I, CHF 2 I, or trans -2-C 4 H 8 , which are efficient colliders). ­(±)-1-fluoro-1-(trifluoromethyl)-2,3-dimethylcyclopropane…”