Photochemistry of chlorobenzene in ice

An unusual photobehaviour of chlorobenzene in ice is reported. Its photolysis at >254 nm provided very different photoproducts from those observed in liquid water where phenol derivatives are almost exclusively isolated. Thus, biphenyl and terphenyl as well as their chlorinated isomers were formed in ice, possibly via a free-radical mechanism, thanks to aggregation of the starting molecules even in very dilute solid solutions. In addition, an unusual multi-step triphenylene photoproduction is reported. Environmental aspects are also discussed.