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Hmc 1- 2010

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  • 1.Homogeneous CatalysisHMC-1- 2010Dr. K.R.KrishnamurthyNational Centre for Catalysis ResearchIndian Institute of Technology, MadrasChennai-600036

2. Homogeneous Catalysis- 1Basics Homogeneous Catalysis- General features Metal complex chemistry- Metals & Ligands bonding & reactivity Reaction cycles Reaction types/ Elementary reaction steps Kinetics & Mechanism 3. Catalysis 1850 Berzelius C a ta ly z e d r x n p ro c e e d in g th r o u g h 1895 Ostwald: A catalyst is aa n in te r m e d ia te substance that changes the rate of a Ea chemical reaction without itself appearing into the productsE a Gc a t a ly z e d Definition: a catalyst is a substance that increases the rate at which a R e a c ta n ts G chemical reaction approaches equilibrium without becoming itself P ro d u c ts permanently involved. Catalysis is a kinetic phenomenon.R e a c tio n C o o r d in a te Catalysis TypesHeterogeneousHomogeneousEnzymatic/Bio Obeys laws of thermodynamics Photo/Electro/Photo-electroPhase transfer 4. Homogeneous Catalysis Reactions wherein the Catalyst components and substrates of the reaction are in the same phase, most often the liquid phase Mostly soluble organometallic complexes are used as catalysts Characterized by high TON & TOF Operate under milder process conditions Amenable to complete spectroscopic characterizationHomogeneous processes without a heterogeneous counterpart:Pd-catalyzed oxidation of ethylene to acetaldehyde (Wacker process)Ni-catalyzed hydrocyanation of 1,3-butadiene to adiponitrile (DuPont)Rh- and Ru-catalyzed reductive coupling of CO to ethylene glycolEnantioselective hydrogenation, isomerization, and oxidation reactions. 5. Catalysis- Heterogeneous Vs HomogeneousAspectHeterogeneous HomogeneousActivityComparableComparableReproducibility Difficulty in reproducibility Reproducible resultsSelectivity Heterogeneous sites. Difficult to control Relatively higher selectivity, easy toselectivity optimize, various types of selectivityReaction conditions Higher temp. & pressure, better thermal Lower temp. (