Reactions of trifluoromethyl radicals. III. Hydrogen abstraction from methyl trifluoroacetate, methyl pentafluoropropionate and methyl heptafluorobutyrate

Abstract

Hydrogen abstraction from CF3COOCH3, C2F5COOCH3 and C3F7COOCH3 by CF3 radicals has been studied in the temperature range 100-210�. The rate constants, based on the value of 1013,36 cm3 mol-1 s-1 for the recombination of CF3 radicals, are given by (kn in cm3 mol-1s-1, E in kJ mol-1, R = 0.008314 kJ K-1 mol-1): Logk1 = (10.81 � 0.16)-(37.52 � 1.27)/2.303RT Logk2 = (10.93 � 0.16)-(38.80 � 1.32)/2.303RT Logk3 = (11.24 � 0.08)-(42.49 � 0.63)/2.303RT The reactivity of the methoxyl groups in these esters is less than those in HCOOCH3 and CH3COOCH3 by a factor of between 2 and 3. This can be explained in terms of intermolecular polar repulsion induced by the fluorine atoms in the esters and the CF3 radical.