Chemical production and trapping of methyl radicals at silica surfaces

Abstract

Hydroxylated silicas react with trimethylaluminium to produce surfaces that give rise to organic radicals on exposure to air or dry oxygen at room temperature. The g-value of the paramagnetic species is 2·0027 ± 0·0003 which suggests that it is a methyl radical. The stability of the radical species on the sample under ambient atmospheric conditions shows that it is trapped on the silica surface. The surface concentration of the trapped species is related to the number of micropores present in the parent silica samples suggesting that the ‘traps’ are surface cracks of molecular dimensions. The surface concentrations of the radicals observed are of the order of 10¹² m.^–2 of solid surface.