Chapter 15: Q 15P (page 772)
What dienes and dienophiles would react to give the following Diels-Alder products?
a)
b)
c)
d)
e)
f)
Short Answer
a)
b)
c)
d)
e)
f)
Chapter 15: Q 15P (page 772)
What dienes and dienophiles would react to give the following Diels-Alder products?
a)
b)
c)
d)
e)
f)
a)
b)
c)
d)
e)
f)
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Get started for freeQuestion: When Br2 is added to buta-1,3- diene at -150C , the product mixture contains 60% of product A and 40% of product B. When the same reaction takes place at 600C , the product ratio is 10% A and 90% B.
a. Propose structures for products A and B (Hint: In many case, an allylic carbocation is more stable than a bromonium ion.)
b. Propose a mechanism to account for formation of both A and B.
c. Show why A predominates at -150C and B predominates at 600C .
d. If you had a solution of pure A, and its temperature were raised to600C , what would you expect to happen ? Propose a mechanism to support your prediction.
Show that the [4+2] Diels-Alder reaction is photochemically forbidden.
Question: When is added to buta-1,3- diene at -150C, the product mixture contains 60% of product A and 40% of product B. When the same reaction takes place at 600C, the product ratio is 10% A and 90% B.
a. Propose structures for products A and B (Hint: In many case, an allylic carbocation is more stable than a bromonium ion.)
b. Propose a mechanism to account for formation of both A and B.
c. Show why A predominates at -150C and B predominates at 600C .
d. If you had a solution of pure A, and its temperature were raised to 600C , what would you expect to happen ? Propose a mechanism to support your prediction.
Question: The central carbon atom of an allene is a member of two double bonds, and it has an interesting orbital arrangement that holds the two ends of the molecule at right angles to each other.
In a strongly acidic solution, cyclohexa-1, 4-diene tautomerizes to cyclohexa-1, 3-diene. Propose a mechanism for this rearrangement, and explain why it is energetically favorable.
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