7. Substitution Reactions

In contrast to the results of Assessment 13.18, when a secondary haloalkane is treated with sodium ethanethiolate, we predict formation of a thioether. How is this rationalized?

Predict the product of the following substitution/addition reactions involving phenoxides. [Because this problem represents a review of current and previous material, section numbers have been provided for your reference.]

(d)

The reaction of an alkyl chloride with potassium iodide is generally carried out in acetone to maximize the amount of alkyl iodide that is formed. Why does the solvent increase the yield of alkyl iodide? (Hint: Potassium iodide is soluble in acetone, but potassium chloride is not.)

The following functional-group interchange is a useful synthesis of aldehydes.

(c) Explain why a nucleophilic reagent such as ethoxide adds to an alkyne more easily than it adds to an alkene.

What is the product of the reaction of bromoethane with each of the following nucleophiles?

a. CH₃CH₂CH₂O⁻

b. CH₃C≡C⁻

What is the product of the reaction of bromoethane with each of the following nucleophiles?

c. (CH₃)₃N

d. CH₃CH₂S^-

Cardura, a drug used to treat hypertension, is synthesized as shown here.

a. Identify the intermediate (A) and show the mechanism for its formation.

Strawberry growers have used large quantities of methyl bromide (b.p. 4 °C) to sterilize the soil before planting their crops. Like some of the freons, methyl bromide can diffuse up into the stratosphere, where it damages the protective ozone layer. Agricultural chemists have suggested using methyl iodide (b.p. 43 °C) as a replacement for methyl bromide. Why is methyl iodide likely to be more toxic to agricultural pests (and people) than methyl bromide? Why is methyl iodide less likely to reach the stratosphere than methyl bromide?

Which substitution reaction takes place more rapidly?

a. CH₃CH₂Br + H₂O or CH₃CH₂Br + HO⁻

Draw all the products of the following reaction: