In an attempt to improve our understanding of the basic mechanisms of the degradation of aromatic pollutants, the photocatalysed reactions of five selected organic systems, namely 2-naphthoic acid (1), 2,6-dichloro-4-vitro aniline (2, dichloran), 4-vitro phenyl acetate (3) 1,3-dially-2-thin-urea (4), and 7-hydroxy-4-methyl coumarin (5) has been investigated in water or acetonitrile/water mixture in the presence of titanium dioxide and oxygen. An attempt has been made to identify the products formed during the photooxidation process through GUMS analysis technique. The photolysis of 2-naphthoic acid (1) showed the formation of 2-formylcinnamaldehyde (11) and 1,2-benzenedicarboxaldehyde (13) whereas 2,6-dichloro-4-vitro aniline (2) gave rise to 2,6-dichloro-4-vitro phenol (14). However, the photolysis of 4-vitro phenyl acetate (3) yielded 4-nitrphenol (15). The illumination of 1,3-diallyl-2-thin-urea (4), on the other hand, led to the formation of 1,3-diallyl urea (19). Product 2,4-dihydroxy acetophenone (25) was identified in case of 7-hydroxy-4-methyl coumarin (5). The products have been identified by comparing the molecular ion and mass fragmentation peaks of the products with those reported in the GC-MS library. A probable mechanism for the formation of the products has been proposed. (c) 2005 Elsevier B.V. All rights reserved.