Die photolytische α-spaltung von benzoinalkyläthern in sauerstoffhaltigem methanol

The primary step in the photolytical α-cleavage of benzoin alkyl ether in oxygen saturated methanol at room temperature is the formation of a benzoyl (1) and an α-alkoxybenzyl radical (2), which react via their peroxi radicals 3 und 4 to the final products yielding perbenzoic acid (5), alkyl benzoate (7), benzaldehyde (11), benzaldehyde dimethylacetal (10) and benzil to 100%. Product analysis of the final products of the photolysis of specifically deuterated benzoin methyl ethers shows that methyl benzoate, benzaldehyde and benzaldehyde dimethylacetal are formed via the α-methoxybenzyl radical (2) while the perbenzoic acid results from the benzoyl radical (1). Both the peroxi radicals 3 and 4 have an independent reaction pathway to the final products. Hydrogen abstraction of 3 and 4 from the solvent methanol give rise to hydroxy methyl radicals which yields formic acid, hydrogen peroxide, performic acid and formaldehyde via their hydroxy methyl peroxi radicals. The reaction pathway of the primary radicals is discussed.