UV Absorption of Conjugated Alkenes

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UV Absorption of Conjugated Alkenes

• Increasing conjugation gives
• longer wavelength absorption
• more intense absorption

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Aromatic Compounds
Substituents shift 255 nm band to higher
wavelength
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UV-Vis

• Which would absorb a longer wavelength of light,
  1,4-pentadiene or 1,3-pentadiene?

Conjugated
Isolated
178 nm
223 nm
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Diels-Alder Reactions
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Why?
The diene is not electron rich enough because it
has an electron withdrawing carbonyl on it.
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Draw the product (A) of the following Diels-Alder
reaction. A is a key intermediate in the
synthesis of the addicting pain reliever
morphine, isolated form the opium poppy.
The Opium Poppy
What is A?
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Opium continued. . .
such a good dienophile?
Why is
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Cortisone (a hormone responsible for the control
of inflammation and the regulation of
carbohydrate metabolism) can be synthesized using
a Diels-Alder reaction along the synthetic
pathway. Draw the diene and dienophile used to
make the intermediate. An arrow shows the
6-membered ring made in the reaction.
Cortisone
Cortisone
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Youll think Im making these compounds up, but
theyre real. The following reactions have been
used to synthesize dieldrin and aldrin (named for
Diels and Alder), two pesticides having a similar
story to DDT. Identify X, Y, and Z in the
reaction scheme.
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The compound shown below is the product formed in
a Diels-Alder reaction between methyl acrylate
(CH2CHCO2CH3) and a diene. Draw the structure
of the diene. (2.5 pts)