Decomposition of Di-t-butyl Peroxide and Kinetics of the Gas Phase Reaction of t-butoxy Radicals in the Presence of Ethylenimine

The reaction of di‐t‐butyl peroxide with ethylenimine has been studied between 129° and 154°C. The t‐butoxy radicals formed by the rupture of the O–O bond of the peroxide, $$({\mathrm{CH}}_3{)}_3\mathrm{COOC}({\mathrm{CH}}_3{)}_3\to {\displaystyle {lim}^{k_1}}\text{2(}{\mathrm{CH}}_3{)}_3\mathrm{CO},$$ are postulated to enter into the following reactions: $$\begin{array}{c}({\mathrm{CH}}_3{)}_3\mathrm{CO}\to {\displaystyle {lim}^{k_2}}{\mathrm{CH}}_3{\mathrm{COCH}}_3+{\mathrm{CH}}_3\\ 2{\mathrm{CH}}_3\to {\displaystyle {lim}^{k_3}}{\mathrm{C}}_2{\mathrm{H}}_6\\ {\mathrm{CH}}_3\mathrm{+(}{\mathrm{CH}}_2{)}_2\mathrm{NH}\to {\displaystyle {lim}^{k_4}}({\mathrm{CH}}_2{)}_2\mathrm{N}+{\mathrm{CH}}_4\\ ({\mathrm{CH}}_3{)}_3\mathrm{CO}\mathrm{+(}{\mathrm{CH}}_2{)}_2\mathrm{NH}\to {\displaystyle {lim}^{k_5}}({\mathrm{CH}}_2{)}_2\mathrm{N}\mathrm{+(}{\mathrm{CH}}_3{)}_3\mathrm{COH}.\end{array}$$ The rate constant for the unimolecular decomposition of the peroxide into t‐butoxy radicals is found to be in the range k₁=6×10¹⁴e^−36,000/RT to k₁=6×10¹⁶e^−40,000/RT sec⁻¹. The activation energies E₄—E₃/2=4.8 kcal/mole and E₂—E₅=12 kcal/mole are calculated from the kinetic data. The complete rate expression for the capture of imine H atom by CH₃ radical, $$k_4{\text{=4.5×10}}^{10}{e}^{\text{−4800/RT}}\mathrm{\hspace{0.17em}(}\mathrm{moles/cc}{)}^{\text{−1}}\hspace{0.17em}{\sec }^{\text{−1}},$$ is obtained by using Gomer and Kistiakowsky's values for k₃=4.5×10¹³ (moles/cc)⁻¹ sec⁻¹ and E₃=0. The activation energy for the thermal decomposition of t‐butoxy radical is about 17 kcal/mole if E₄ and E₅ of similar type H capture mechanisms are assumed equal.