Effect of Phase on Hot Hydrogen Atom Abstraction Reaction with Solid Isobutane as Studied by Electron Spin Resonance Spectroscopy

The effect of phase on the hot-hydrogen-atom abstraction reaction with isobutane at 77°K has been studied by electron spin resonance spectroscopy in the photolysis and the radiolysis of solid isobutane containing hydrogen iodide. While only the isobutyl radical is formed by the UV-illumination of isobutane–hydrogen iodide systems in the polycrystalline state, the tertiary butyl radical, accompanied with a small amount of isobutyl radicals, is produced from isobutane-methylcyclohexane-hydrogen iodide systems in the glassy state. The hot hydrogen atom produced by dissociative electron attachment to hydrogen iodide abstracts the tertiary hydrogen atom from isobutane at 77°K, independent of whether the matrix is polycrystalline or glassy. It appears that the H-abstraction reaction from isobutane by hot hydrogen atoms depends upon the energy of the hot hydrogen atoms.