Polymerization of N‐vinylcarbazole in presence of carbon tetrabromide. III. Oxygen‐induced photodimerization in methanol solution

The rate of photochemical dimerization of N‐vinylcarbazole (NVC) in methanol solution which takes place only in the presence of oxygen is greatly increased by addition of carbon tetrabromide (CTB). Similar high rates are obtained with sensitizers like benzil and biacetyl. The mechanism of formation of the cyclic dimer, trans‐1,2‐dicarbazole‐9‐yl‐cyclobutane (I), and of the open‐chain dimeric dimethoxy derivative, 1,4‐dicarbazole‐9‐yl‐1′,4′‐dimethoxy‐n‐butane (II), is discussed in some detail.