9. Alkenes and Alkynes

What is the major product(s) of each of the following reactions?

d.

Propose mechanisms for the following reactions. In most cases, more products are formed than are shown here. You only need to explain the formation of the products shown, however.

(b)

What is the product of the following reaction?

Identify two different alcohols that can be dehydrated (one with rearrangement) to form the alkene shown.

Predict the major product of the following elimination reactions.

(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.

(b)

Which of the following best describes a dehydration synthesis reaction?

Predict the products of the sulfuric acid-catalyzed dehydration of the following alcohols. When more than one product is expected, label the major and minor products.

(d) 1-isopropylcyclohexanol

(e) 2-methylcyclohexanol

Propose mechanisms for the following reactions.

(a)

When heated with H₂SO4, both 3,3-dimethyl-2-butanol and 2,3-dimethyl-2-butanol are dehydrated to form 2,3-dimethyl-2-butene. Which alcohol dehydrates more rapidly?

Explain why the acid-catalyzed dehydration of an alcohol is a reversible reaction, whereas the base-promoted dehydrohalogenation of an alkyl halide is an irreversible reaction.

Which of the following is an example of a dehydration reaction?

The acid-catalyzed hydration we learned here in Chapter 8 is reversible:

(d) How might you shift the equilibrium to the right?

Write a mechanism that explains the formation of the following product. In your mechanism, explain the cause of the rearrangement, and explain the failure to form the Zaitsev product.

What is the primary result of a dehydration synthesis reaction on carbohydrates?