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Alkadienes and Polyunsaturated Hydrocarbons

Alkadienes and Polyunsaturated Hydrocarbons. Molecule of the Week. Cytostatin inhibits an enzyme that is linked to cancer. Solomons and Fryhle 13.6 – 13.10 Page 1. Examples of Differing Dienes. Page 2. C 5 H 8.

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Alkadienes and Polyunsaturated Hydrocarbons

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  1. Alkadienes and Polyunsaturated Hydrocarbons Molecule of the Week Cytostatin inhibits an enzyme that is linked to cancer Solomons and Fryhle 13.6 – 13.10 Page 1

  2. Examples of Differing Dienes Page 2

  3. C5H8 On his second voyage, Columbus saw children playing with balls made from the sap of local trees. Joseph Priestly called the material the balls were made of rubber, because it would erase pencil marks by rubbing. Michael Faraday, one of the nineteenth centuries greatest scientists, determined an empirical formula for rubber of C5H8. This is the formula for the diene isoprene. Rubber is a natural polymer of isoprene. Crude rubber, latex, collected from the rubber tree Hevea brasiliensis is an aqueous emulsion of the polymer. It is washed, dried and coagulated to give raw rubber, each chain of which consists of ca. 5000 isoprene units. All of the double bonds in natural rubber are cis-, a corresponding trans- polymer has quite different properties.            Page 3

  4. Page 4

  5. 1.34 A Why 1.34 A 1.47 A o Note A: A Conjugated Dienes C-C  Bond > sp3 – sp3 > sp2-sp2 > sp-sp 1.54 A 1.20 A Why What About C2-C3?? Page 5

  6. Page 6

  7. Molecular Orbital Description of Ethene * E  Page 7

  8. Cation Molecular Orbital Description of 1,3-Butadiene Anion 4* 3 * 2 LUMO: Lowest unoccupied molecular orbital HOMO: Highest occupied molecular orbital 1 Page 8

  9. Conjunction of P-Orbitals Page 8a

  10. Page 9

  11. See Solomons and Fryhle 13.9 max * * *    A: Absorbance C: molar concentration of sample : extinction coeff. L” path length Page 10

  12. See Solomons and Fryhle 13.10 Electrophilic Attack on Conjugated Dienes: Products Note: Markovnikov addition New! Page 11

  13. Electrophilic Attack on Conjugated Dienes: Mechanism Page 12

  14. Electrophilic Attack on Conjugated Dienes: Mechanism Page 13

  15. -80 oC 80% 20% Page 14

  16. Schematic Illustration of Free-Energy vs. Rxn Coordinate for 1,4 and 1-2 addition Of HBr to 1,3-butadiene 1,4-addition Product Page 15

  17. Problem from Solomons and Fryhle 13.34 - Provide a mechanism to accounts for the formation of CICH2CH=CHCH2OCH3 and CICH2CH(OCH3)CH=CH2 upon treatment of 1,3-butadiene with CI2 in methanol. Page 16

  18. Problem from Solomons and Fryhle 13.23 Page 17

  19. Problem from Solomons and Fryhle 13.20 What is Rxn Mechanism and Products? Page 18

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