Mechanism of the intramolecular hydrogen transfer reaction at ground and excited state of tert-butyl radical: An ESR and DFT study

Hydrogen transfer reactions at the ground and excited states of tert-butyl radical to form iso-butyl radical have been investigated by means of ab initio calculation and electron spin resonance (ESR) spectroscopy. It was found that tert-butyl radical irradiated with 254 nm ultraviolet light converts quite efficiently to iso-butyl radical. Also, it was suggested that this conversion occurs as an intramolecular hydrogen transfer from a methyl group of tert-butyl radical to a radical site (central carbon atom). The theoretical calculations showed that barrier height of hydrogen transfer at the excited state is significantly lower than that of ground state. The mechanism of internal hydrogen atom conversion from tert-butyl to iso-butyl radicals was discussed.