Photolysis of 4-chloroanisole in the presence of oxygen: Formation of the 4-methoxyphenylperoxyl radical

The photochemistry of 4-chloroanisole was studied in cyclohexane, with and without molecular oxygen. The triplet state is the main transient in argon purged solutions. In air equilibrated conditions the triplet state was not detected and a new broad absorption band was observed above 450 nm. This absorption was assigned to the 4-methoxyphenylperoxyl radical. The formation of phenylperoxyl radicals after direct photolysis of the parent chlorinated compound in the presence of oxygen is reported here for the first time. Anisole is one of the main photoproducts in both conditions. Bicyclohexane was detected only in argon purged conditions while cyclohexyl ether is only formed in the presence of molecular oxygen. The formation of phenylperoxyl radicals after direct photolysis of chloroaromatics can be used to detect the homolytic cleavage of the C–Cl bond.