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Catalytic Hydrogenation of Alkenes

Catalytic Hydrogenation of Alkenes. Catalyst with Hydrogen and alkene adsorbed. Hydrogen inserted into C = C. Alkane product released from catalyst. Catalyst with Hydrogen adsorbed. Alkene + H2 → Alkane. Heterogeneous catalyst Pt. Pd. Ni-tinely divided metal SYN addition of hydrogen.

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Catalytic Hydrogenation of Alkenes

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  1. Catalytic Hydrogenation of Alkenes Catalyst with Hydrogen and alkene adsorbed Hydrogen inserted into C = C Alkane product released from catalyst Catalyst with Hydrogen adsorbed Alkene + H2 → Alkane Heterogeneous catalyst Pt. Pd. Ni-tinely divided metal SYN addition of hydrogen

  2. Heat evolved upon catalytic hydrogenation (△Ho) A MEASURE OF ALKENE STABILITY ALKENE C4H8 ALKANE C4H10 EXOTHERMIC H2/Pd-C ENERGY (-) 30.3 kcal/mol (-) 28.3 kcal/mol (-) 27.4 kcal/mol Best to compare compounds that react to form same alkane Trans > Cis > Geminal

  3. SUMMARY OF ALKENE CHEMISTRY (illustrated with 1-methyl cyclopent-1-ene to emphasize transformation stereochemistry)

  4. POLYOL NATURAL PRODUCTS CELLULOSE ERYTHRONOLIDE A (ERYTHROMYCIN A) Antibiotic AMPHOTERICIN B Antifungal

  5. NATURAL PRODUCTS WITH ALKENE FUNCTIONALITY g-Bisabolene A sesquiterpene found in the essential oils of a number of plants Limonene A monoterpene common in citrus fruits Cembrene A diterpene from pine needles Caryophyllene A constituent of clove oil Carvone Spearmint oil b-Carotene (A vitamin) A tetraterpene bright orange in color and the precursor to the visual pigment retinal Vitamin A (vision)

  6. MARKOVNIKOV and ANTI-MARKOVNIKOV ADDITION TO ALKENES Markovnikov Anti- Markovnikov In the dark, in the absence of peroxides polar solvents to promote formation of polar intermediate. Most substituted carbonium ion intermediate gives most substituted bromide product In the presence of peroxides and heat or light to promote homolytic cleavage of O-O bond. Most substituted radical intermediate gives least substituted bromide product

  7. ALKENE POLYMERIZATION - SPECIAL TOPIC POLYMER (trade name) STRUCTURE MONOMER ethene Polyethylene(polythene) propene polypropylene Chloroethene (vinyl chloride) PVC(poly)vinyl chloride acrylonitrile Orlon(acrilan) tetrafluoroethene TEFLON Phenylethene(styrene) POLYSTYRNEN LUCITE(Plexiglass) methylmethacrylate 1,1-dichloroetheneand 1-chloroethene Random co-polymerSARAN WRAP

  8. FREE RADICAL POLYMERIZATION INITIATION, PROPAGATION (POLYMERIZATION) and TERMINATION STEPS INITIATION POLYMERIZATION TERMINATION

  9. FREE RADICAL POLYMERIZATION FREE RADICAL POLYMERIZATION INITIATION, PROPAGATION (POLYMERIZATION) and TERMINATION STEPS INITIATION, PROPAGATION (POLYMERIZATION) and TERMINATION STEPS INITIATION INITIATION POLYMERIZATION POLYMERIZATION TERMINATION TERMINATION

  10. CATIONIC POLYMERIZATION INITIATION, PROPAGATION (POLYMERIZATION) and TERMINATION STEPS INITIATION Good monomer for cationic polymerization..Why? What about tetrafluoroethene? POLYMERIZATION TERMINATION

  11. CHOLESTEROL BIOSYNTHESIS Squalene epoxidase Squalene Oxidosqualene cyclase CHOLESTEROL

  12. Oxidosqualene cyclase

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