Successive photocyanation was found to be a general reaction when chlorinat
ed aromatic compounds were photolyzed with sodium cyanide. The products wer
e polycyanated hydroxychloro compounds with various degrees of chlorine rep
lacement. Although the products from some substrates could be isolated, ide
ntified, and characterized, most reactions proceeded with low regioselectiv
ity, which limits their synthetic potential. Quantum yields of substrate di
sappearance increased with the number of chlorine substituents on a substra
te, and followed the expected relationship phi(-1) proportional to [CN-](-1
). In some cases, phi depended also on the concentration of the chloro comp
ound, indicating the involvement of excimers, although the major reaction c
hannel appears to be S(N)2Ar*. Sensitization and quenching experiments esta
blished the triplet excited state to be reactive for ail substrates tested.