100% selective yield of m-nitroaniline by rutile TiO2 and m-phenylenediamine by P25-TiO2 during m-dinitrobenzene photoreduction

• Selective reduction of m-DNB to 100% m-NA by R-TiO2 under 8 h UV irradiation
• P25-TiO2 catalyst gives 100% m-PDA from m-DNB under 4 h of UV irradiation.
• m-NA yield from m-DNB reduction increases with the increased R-TiO2 content.
• Iso-propanol is found to be the best solvent for both m-NA and m-PDA formation.

Photoreduction of m-dinitrobenzene (25 μmol) in the deaerated aqueous iso-propanol exhibits 100% selective yield of m-nitroaniline (25 μmol) by rutile TiO2 (50 mg) or m-phenylenediamine (25 μmol) by P25-TiO2 separately under 8 and 4 h of UV light irradiation (125 W Hg arc, 10.4 mW/cm2), respectively. It revealed that insertion of a second –NO2 in nitrobenzene ring has an important role in expediting –NO2 reduction to –NH2 as compared to a negligible reduction of nitrobenzene under similar conditions, indicating that electron withdrawing groups lower the electron density on –NO2 present on meta position and favor quick reduction of the –NO2 group.

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