07 alkadienes

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07 alkadienes

  1. 1. Organic chemistry I Zdeněk Friedl Chapter 7 Alkadienes Solomons & Fryhle: Organic Chemistry 8th Ed., Wiley 2004
  2. 2. Alkadienes• structure of alkadienes• stability of alkadienes• reaction scheme of alkadienes• regioselectivity of addition AE reactions• kinetic vs. thermodynamic controlled reactions• Diels-Alder reactions• regiospecifity of Diels-Alder reactions• endo vs. exo products of Diels-Alder reactions 2
  3. 3. The π-electron structure of 1,2 , 1,3 and 1,4-alkadienes cumulated, conjugated, isolated dienes 3
  4. 4. The π- orbital structure of 1,3-butadiene conjugation of π-orbitals a lower energy 4
  5. 5. Heats of hydrogenation of alkenes and alkadienes I 5
  6. 6. Heats of hydrogenation of alkenes and alkadienes IIheats of hydrogenation of 2 moles of 1-butene and 1 mole of 1,3-butadiene The difference of 15 kJ mol-1 a conjugation energy 6
  7. 7. The reaction scheme of alkadienes AE ARR CH = CH CH2 CH = CH2 AE (1,2- / 1,4- ) 4 3 2 1R CH = CH CH = CH2 (AR) == cycloaddition 7
  8. 8. AE Regioselectivity of addition reactions on conjugated 1,3-alkadienes 8
  9. 9. AE Kinetic vs. thermodynamic controlled reactions 1,2- and 1,4-addition reactions 9
  10. 10. AE Kinetic vs. thermodynamic controlled reactions An importance of ∆G‡ vs. ∆G° energies ∆G‡1,4 > ∆G‡1,2 ∆G°1,2 > ∆G°1,4 10
  11. 11. Diels-Alder reactions(4+2)π 1,4-cycloaddition reactions 11
  12. 12. Stereospecifity of Diels-Alder reactions 12
  13. 13. Endo vs. Exo products of Diels-Alder reactions 13

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