This document discusses alkadienes and their reactions. It covers the structure of alkadienes, their stability, and common reaction schemes like addition and Diels-Alder reactions. Specifically, it examines the regioselectivity of addition reactions on conjugated alkadienes and how kinetic vs. thermodynamic control affects 1,2 and 1,4 additions. It also explores the regioselectivity, endo vs. exo product formation, and stereospecificity of Diels-Alder reactions involving alkadienes.

1. Organic chemistry I
Zdeněk Friedl
Chapter 7
Alkadienes
Solomons & Fryhle: Organic
Chemistry 8th Ed., Wiley 2004

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
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3. The π-electron structure of 1,2 , 1,3 and 1,4-alkadienes
cumulated, conjugated, isolated dienes
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4. The π- orbital structure of 1,3-butadiene
conjugation of π-orbitals a lower energy
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5. Heats of hydrogenation of alkenes and alkadienes I
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6. Heats of hydrogenation of alkenes and alkadienes II
heats 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
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7. The reaction scheme of alkadienes
AE
AR
R CH = CH CH2 CH = CH2
AE (1,2- / 1,4- )
4 3 2 1
R CH = CH CH = CH2 (AR)
==
cycloaddition
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8. AE Regioselectivity of addition reactions
on conjugated 1,3-alkadienes
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9. AE Kinetic vs. thermodynamic controlled reactions
1,2- and 1,4-addition reactions
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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
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11. Diels-Alder reactions
(4+2)π 1,4-cycloaddition reactions
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12. Stereospecifity of Diels-Alder reactions
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13. Endo vs. Exo products of Diels-Alder reactions
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