title: Photocatalytic degradation of N-heterocyclic aromatics-effects of number and position of nitrogen atoms in the ring.
abstract: This study demonstrates the influences of position, number of nitrogen (N) atoms and -C-N- or -N=N- linkage present in the six membered heterocyclic compounds such as pyridine, pyrazine, and pyridazine on their photocatalytic degradation by Au, Ag, and Fe(+2) deposited TiO(2) photocatalyst. The photodegradation rate of these heterocyclic compounds follow the order pyridine > pyrazine > pyridazine due to the different extent of hydroxylation and difference in position and number of N atoms in the aromatic moiety. The Au photodeposition significantly improved the TiO(2) photoactivity as compared to Ag and Fe(+2) loading. The presence of two N atoms in pyrazine and pyridazine as compared to one N atom in pyridine hamper the nucleophilc attack of OH radicals in comparison to easy hydroxylation of pyridine ring. There is 1 N atom, 4C-C, 1C-N and 1C=N bond in pyridine, 2 N atoms in the 1 and 4 positions, 2C-C, 2C-N bonds and 2C=N bonds in pyrazine, and pyridazine ring contains 2 N atoms in the 1 and 2 positions, 3C-C, 1N-N bond and 2C=N bonds. The bond strength/energy decreases gradually as: C=N- (615 KJ/mol) > -N=N- (418 KJ/mol) > -C-C- (347 KJ/mol) > -C-N- (305 KJ/mol) > -N-N- (163 KJ/mol). As pyridine has 1C-N, 1C=N, and no N-N bond, it photodegrades easily as compared to 1 N-N and 2C=N bonds of pyridazine of lowest photodecomposition rate. The improved photoactivity of Au-TiO(2) is explained on the basis of its favorable redox potential, work function, and electron-capturing capacity, etc.
authors: School of Chemistry and Biochemistry, Thapar University, Patiala, 147-004, Punjab, India.
authors: Jasmeet
authors: J
authors: Kaur
authors: Bonamali
authors: B
authors: Pal
mesh_terms: D002384:Catalysis; D006571:Heterocyclic Compounds / Q000737:chemistry*; D007700:Kinetics; D015394:Molecular Structure; D009584:Nitrogen / Q000737:chemistry*; D010782:Photolysis; D011719:Pyrazines / Q000737:chemistry; D011724:Pyridazines / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D055549:Volatile Organic Compounds / Q000737:chemistry*
chemical_list: D006571:Heterocyclic Compounds; D011719:Pyrazines; D011724:Pyridazines; D011725:Pyridines; D055549:Volatile Organic Compounds; C062482:pyridazine; D009584:Nitrogen; C023666:pyridine
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