Photocatalysed reaction of few selected organic systems in presence of titanium dioxide

Abstract

The photocatalysed reaction of five selected organic systems, namely 2,2′-dinitro biphenyl ( 1), N, N′-dimethyl-4-nitroso aniline ( 2), 4-dimethyl amino benzaldehyde ( 3), phthalaldehyde ( 4) and tetramethyl benzoquinone ( 5) has been investigated in 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 GC/MS analysis technique. The photolysis of 2,2′-dinitro biphenyl ( 1) leads to the formation of 2-hydroxy-2′-nitro biphenyl ( 6), 2,2′-dihydroxy biphenyl ( 7) and 2-biphenyl amine ( 11); whereas, N, N′-dimethyl-4-nitroso aniline ( 2) gave rise to N, N′-dimethyl-4-nitro aniline ( 14) and N, N′-dimethyl-1,4-benzenediamine ( 15). However, the photolysis of 4-dimethyl amino benzaldehyde ( 3) yielded only a demethylated product ( 18). The illumination of phthalaldehyde ( 4), on the other hand, led to the formation of two products such as 1(3H)-isobenzofuranone ( 24) and 2-formyl-benzoic acid ( 21). Two intermediate products, tetramethyl hydroquinone ( 35) and 2,5-furandione-3,4-dimethyl ( 34) have been identified in case of tetramethyl benzoquinone ( 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.