Strahlenchemie von alkoholen—IX : Die UV-photolyse (λ = 185 nm) von methanol in flüssiger phase

Abstract

The UV photolysis (λ = 185 nm) of liquid methanol yields hydrogen, glycol, formaldehyde, methane and traces of ethane in quantum yields of 0·83, 0·78, 0·058, 0·05 and 0·002 resp. (related to φ(H 2) = 0·4 of the ethanol-actinometer (5 mole/1 in water)). The isotopic distribution of the hydrogen (85% HD) formed in the photolysis of CH 3OD shows, that as in the gasphase 2 the scission of the OH-bond (1) is the major process. CH 3OH + h v (λ = 185 nm) → CH 3O • + H • (1) In methanoi-water mixtures (nearly all the light of the wavelength λ = 185 nm is absorbed by methanol) the quantum yields of hydrogen, glycol, methane and ethane are greatly reduced, while the formaldehyde yield remains unaffected. In 1 molar solution φ(H 2) = 0·42, φ(glycol) = 0·32 and φ(CH 4) = 6 x 10 −4 is obtained. Ethane cannot be detected.