10. Addition Reactions

The acid-catalyzed dehydration we learned in this chapter is reversible, as shown below.

(b) Without looking back, how do you know this mechanism is correct?

The pK_a values of the carboxylic acid groups of oxaloacetic acid are 2.22 and 3.98.

b. The amount of hydrate present in an aqueous solution of oxaloacetic acid depends on the pH of the solution: 95% at pH 0, 81% at pH 1.3, 35% at pH 3.1, 13% at pH 4.7, 6% at pH 6.7, and 6% at pH 12.7. Explain this pH dependence.

How could the following compounds be prepared using an alkene as one of the starting materials?

c.

How could the following compounds be prepared using an alkene as one of the starting materials?

e.

Using any alkene and any other reagents, how would you prepare the following compounds?

e.

Which compound is hydrated more rapidly?

Propose a mechanism for the following reaction:

Answer the following questions about the mechanism for the acid-catalyzed hydration of an alkene:

a. How many transition states are there?

b. How many intermediates are there?

c. Which step in the forward direction has the smallest rate constant?

What stereoisomers are obtained from each of the following reactions?

b.

How could the following compounds be prepared using an alkene as one of the starting materials?

a.

What is the major product of the reaction of 2-methyl-2-butene with each of the following reagents?

g. H₂O + H₂SO₄

Propose a mechanism to show how 3,3-dimethylbut-1-ene reacts with dilute aqueous H₂SO₄ to give 2,3-dimethylbutan-2-ol and a small amount of 2,3-dimethylbut-2-ene.

HINT: When predicting products for electrophilic additions, first draw the structure of the carbocation (or other intermediate) that results from electrophilic attack.

Predict the products of the following hydration reactions.

b. 2-phenylpropene + dilute acid

c. 1-phenylcyclohexene + dilute acid

Propose mechanisms consistent with the following reactions.

(b)

Often, compounds can be synthesized by more than one method. Show how this 3° alcohol can be made from the following:

(b) two different alkenes