The Reactions of Methyl Radicals. I. The Photolysis of Acetone

Abstract

The photolysis of acetone has been investigated between 100°C and 300°C. The rates of production of carbon monoxide, methane and ethane have been measured over a range of acetone pressures from 3.9 to 100 mm and with a thirty‐fold variation of light intensity. The methane and ethane formed can be quantitatively accounted for by the equations $${\mathrm{CH}}_3+{\mathrm{CH}}_3={\mathrm{C}}_2{\mathrm{H}}_6\mathrm{,\hspace{0.17em}\hspace{0.17em}}{\mathrm{CH}}_3+{\mathrm{CH}}_3{\mathrm{COCH}}_3={\mathrm{CH}}_4+{\mathrm{CH}}_2{\mathrm{COCH}}_3.$$ It is found that E₃—½E₂=9.7 kcal., where E₂ and E₃ are the activation energies of the above reactions. The photolysis of deuterated acetone has also been investigated, here E₃′—½E₂′=10.3 kcal. The collision theory ``steric'' or ``P'' factor for the second reaction is less than 10⁻³ in each case.