4-AlkenesH2H3O

4-AlkenesH2H3O - Using Hammond's Postulate to Explain...

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Unformatted text preview: Using Hammond's Postulate to Explain Regioselectivity of HX Addition A H3C H3C H C C H H Br B Standard Free Energy, !G Standard Free Energy , !G Reaction Coordinate Reaction Coordinate Path A Path B How can we increase the rate of a reaction? **_______ determines rate and _______ set by Mother nature. 1. Increase temperature. Increase the number of molecules with sufficient energy to cross barrier - therefore increase rate. Propability of a particle with specific kinetic energy Kinetic Energy 2. In biological system temperature increase not always possible. Second option:_______________________. Standard Free Energy, !G Reaction Coordinate Propability of a particle with specific kinetic energy Kinetic Energy 2. Addition of H2 to Alkenes = Hydrogenation H + H2 H No reaction observed - !G too high - too slow. H + H2 (g) H H H H H Solvents = EtOH, hexanes, acetic acid Heterogeneous catalyst: Advantages: **Easy to handle/store **Purification simple Disadvantage: Not very selective O Pd/C, H2(g) Ethanol, RT Mechanism of Heterogeneous Alkene Hydrogenation Homogeneous Catalysts Also Useful: Wilkinson's catalyst Bruice, Organic Chemistry Industrially Important O OH 45% linoleic acid 35% oleic acid partially hydrogenated = crisco O OH O OH Ni, H2(g) O OH O OH Main constituents of corn oil Saturated and Trans fats both increase "bad" cholesterol Trans fats also decreases "good"cholesterol (carries cholesterol back to liver and away from arteries). Increased risk of coronary heart disease http://www.americanheart.org/presenter.jhtml?identifier=3046430 3. Addition of HOH to an Alkene (alkenes to alcohols) Three Methods A. Hydration (4.9B) B. Oxymercuration/Reduction (5.3A) C. Hydroboration/Oxidation (5.3B) 3A) Acid-catalyzed hydration : E+ = H3O+ ...
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This note was uploaded on 05/13/2010 for the course CHEM 151L taught by Professor Roy,christopher during the Fall '08 term at Duke.

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4-AlkenesH2H3O - Using Hammond's Postulate to Explain...

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