a) b) Figure 3. Structure of the gold catalyst deposited on the Mo-TiO2 support. a) Bilayer structure; b) monolayer structure Problem 10. Kinetic puzzles Propose the mechanisms for the reactions given below. Prove that your mechanisms are consistent with the experimentally observed rate laws. Use proper approximations if necessary. 1. Oxidation of bromide ion by permanganate in acidic solution 2MnO4– + 10Br– + 16H+ = 2Mn2+ + 5Br2 + 8H2O a) at low concentrations of Br– and H+ = r kс(MnO4–)с2(Br–)с3(H+) b) at high concentrations of Br– and H+ = r kс(MnO4–)с(Br–)с(H+) where are the total concentrations of reactants. In both cases <<с(Br–), с с(MnO4–) с(H+). 2. Oxidation of benzamide by peroxydisulfate in the presence of Ag+ ions in water-acetic acid solution 2C6H5CONH2 + 2H2O + 3S2O82– = 2C6H5COOH + 6SO42– + N2 + 6H+ = r k[Ag+][S2O82–] 3. Oxidation of formate ion by peroxydisulfate in water solution HCOO– + S2O82– = CO2 + 2SO42– + H+ = r k[HCOO–]1/2[S2O82–] 4. Oxidation of azide ion by iodine in carbon disulfide solution I2 + 2N3– = 3N2 + 2I– = r k[N3–] 5. Condensation of aldehydes with acryl esters in the presence of the base – 1,4-diazabicyclo[2.2.2]octane (DABCO) in tetrahydrofurane solution
a) b) Figure 3. Structure of the gold catalyst deposited on the Mo-TiO2 support. a) Bilayer structure; b) monolayer structure Problem 10. Kinetic puzzles Propose the mechanisms for the reactions given below. Prove that your mechanisms are consistent with the experimentally observed rate laws. Use proper approximations if necessary. 1. Oxidation of bromide ion by permanganate in acidic solution 2MnO4– + 10Br– + 16H+ = 2Mn2+ + 5Br2 + 8H2O a) at low concentrations of Br– and H+ r = kс(MnO4–)с2(Br–)с3(H+) b) at high concentrations of Br– and H+ r = kс(MnO4–)с(Br–)с(H+) where с are the total concentrations of reactants. In both cases с(MnO4–) <<с(Br–), с(H+). 2. Oxidation of benzamide by peroxydisulfate in the presence of Ag+ ions in water-acetic acid solution 2C6H5CONH2 + 2H2O + 3S2O82– = 2C6H5COOH + 6SO42– + N2 + 6H+ r = k[Ag+][S2O82–] 3. Oxidation of formate ion by peroxydisulfate in water solution HCOO– + S2O82– = CO2 + 2SO42– + H+ r = k[HCOO–]1/2[S2O82–] 4. Oxidation of azide ion by iodine in carbon disulfide solution I2 + 2N3– = 3N2 + 2I– r = k[N3–] 5. Condensation of aldehydes with acryl esters in the presence of the base – 1,4-diazabicyclo[2.2.2]octane (DABCO) in tetrahydrofurane solution
Preparatory_problems_IChO_2013.docx