Pyrolysis of 2-phenylethylamines heats of formation of aminomethyl radicals R_2NCH_2^• (R = H, CH_3)

A kinetic study of the very low-pressure pyrolysis of ethylbenzene (I), 2-phenylethylamine (II), and N,N-dimethyl 2-phenylethylamine (III) (1) PhCH_2CH_3 = PhCH_2^• + ^•CH_3 (2) PhCH_2CH_2NH_2 = PhCH_2^• + H_2NCH_2^• (3) PhCH_2CH_2N(CH_3)_2 = PhCH_2^• + (CH_3)_2NCH_2^• above 900 K yields the heats of formation of aminomethyl (A) and N,N-dimethylaminomethyl (B) radicals: ΔH_(ƒ, 300 K)(A) = 30.3 and ΔH_(ƒ, 300 K)(B) = 27.5 kcal/mol. The difference of stabilization energies E_s, (relative to methyl radicals): Δ = E_s(B) − E_s(A) = (2 ± 1) kcal/mol, conforms to similar effects in methyl substituted alkyl and amino free radicals.