9. Alkenes and Alkynes

Propose mechanisms for the following reactions. Additional products may be formed, but your mechanism only needs to explain the products shown.

(c)

Indicate which alcohol in each pair undergoes an elimination reaction more rapidly when heated with H₂SO₄.

e.

Propose a mechanism for each reaction.

(c)

Predict the product(s) of the reactions shown.

(b)

Identify the alcohol(s) that would produce the following alkenes under the given conditions.

(c)

Indicate which alcohol in each pair undergoes an elimination reaction more rapidly when heated with H₂SO₄.

c.

When using sulfuric acid, but in the absence of other nucleophiles like water or bromide ion, less stable alkenes can be isomerized to their more stable isomer. Provide a mechanism for these acid-catalyzed isomerization reactions. [This is one illustration of the principle of microscopic reversibility.]

(a)

Explain why (S)-2-butanol forms a racemic mixture when it is heated in sulfuric acid.

Write a balanced equation for each reaction, showing the major product you expect.

(c)

Show the product(s) you expect from dehydration of the following alcohols when they are heated in sulfuric or phosphoric acid. In each case, use a mechanism to show how the products are formed.

(a)