PRIMARY YIELDS OF CH3.O AND .CH2OH RADICALS RESULTING IN THE RADIOLYSIS OF HIGH-PURITY METHANOL

The triethylsilane radical R3.Si, produced by radiolysis in an airfree methanol/silane-system, acts as a specific scavenger for the CH3.O and .CH2OH transients with rate constants, k14(R3.Si + CH3.O) = 1.1 x 10(8) dm3 mol-1 s-1 and k15(R3.Si + .CH2OH) = 0.7 x 10(8) dm3 mol-1 s-1, resulting in R3Si-OCH3 (triethylmethoxysilane) and R3Si-CH2OH (triethylsilylmethanol). By increasing the silane concentration (range: 10(-2)-6 mol dm-3 R3SiH) the formation of the otherwise major products of methanol radiolysis, formaldehyde and glycol, is successively reduced to nil. The yield of R3Si-CH2OH, studied under the same conditions, passes a maximum at about 0.8 mol dm-3 R3SiH and then also diminishes. On the other hand, the yield of R3Si-OCH3 is increased correspondingly and reaches an interpolated value of G = 3.75 +/- 0.1 at 4 mol dm-3 R3SiH. This indicates that the radical CH3.O (G = 3.75 +/- 0.1) is the primary radiolytic transient of methanol in addition to H, e(sol)- etc., but not .CH2OH species. The latter one is obviously formed by the secondary reaction: CH3.O + CH3OH --> CH3OH + .CH2OH.