Reactions of radicals containing fluorine. Part 2.—Hydrogen and deuterium atom abstraction from methylamine and trideuteromethylamine by trifluoromethyl radicals
The reactions of trifluoromethyl radicals with methylamine and trideuteromethylamine have been studied in the temperature range 30–160°C in order to determine the rates at which hydrogen and deuterium atoms are abstracted from the molecules. With methylamine, radical attack is favoured at the alkyl position, and substitution of deuterium for hydrogen alters the positional reactivity by an amount in accord with the zero-point energy difference. The pre-exponential factors for attack at the nitrogen site have been explained in terms of a low steric factor due to repulsion forces between the polar molecule and the radical. Arrhenius parameters (based upon a value of 1013.34 mole–1 cm3 sec–1 for the rate constant of combination of trifluoromethyl radicals ) have been measured for the reactions : CF3+CD3NH2→CF3H+CD3NH 9.94±0.22 4.4±0.4, CF3+CD3NH2→CF3D+CD2NH2 11.03±0.09 6.1±0.2, CF3+CH3NH2→CF3H+(CNH4) 10.79±0.16 4.2±0.3, CF3+CH3NH2→CF3H+CH2NH2 10.72±0.39 4.2±0.6, and have been calculated for NHCH3+CF3H→NH2CH2+CH3 9.9 18.4, (units of A, mole–1 cm3 sec–1; and E, kcal mole–1).