Pyrolysis of ethylenediamines. The stabilization energies of aminomethyl and N,N-dimethylaminomethyl radicals

Abstract

Rates of carbon-carbon bond-fission reactions in ethylenediamine (I) and N,N,N',N'-tetramethylethylenediamine (II), H_2NCH_2-CH_2NH_2 = 2H_2NCH_2- and Me_2NCH_2-CH_2NMe_2 = 2Me_2NCH_2., have been measured under very low-pressure conditions between 920 and 1170 K. The high-pressure Arrhenius expressions log (k_1, s^(-1)) = 15.5 - 65.1/θ and log (k_2, s^(-1)) = 15.6 - 63.2/θ (θ = 4.575 x 10^(-3) T kcal/mol) have been derived from present measurements, thermochemical data, and model estimates of k_(-1_ and k_(-2). These parameters lead to the heats of formation of aminomethyl (A) and N,N-dimethylaminomethyl (B) radicals ΔH_(f,298)(A)= 31.1 and ΔH_(f,298)(B)= 29.7 kcal/mol, to bond dissociation energies in the parent amines BDE(H_2NCH_2-H) = 88.7 and BDE(Me_2NCH_2-H) = 87.5 kcal/mol and to stabilization energies E_s, relative to the methyl radical, of E_s(A) = 16.4 and E_s(B) = 17.6 kcal/mol.

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