9. Alkenes and Alkynes

Show how the following compounds can be prepared, using ethyne as one of the starting materials:

3. 2-methyl-3-hexyn-2-ol

Using the given starting material, any necessary inorganic reagents and catalysts, and any carbon-containing compounds with no more than three carbons, indicate how each of the following compounds can be prepared:

c.

Show the products of the following acetylide alkylation reactions. [Make sure your product has the correct number of carbons.]

(d)

Calculate for the following acid–base reactions. Which is the best base to use to deprotonate acetylene and make the acetylide anion?

(c)

Suggest reagents you might use to generate the product from the given reactant.

(b)

Suggest reagents you might use to generate the product from the given reactant.

(a)

Show how you would accomplish the following synthetic transformations. Show all intermediates.

c. but-1-yne → oct-3-yne

Suggest an acetylide ion and a carbonyl that might be used to make the following products.

(a) oct-4-yn-3-ol

Show the products of the following acetylide alkylation reactions. [Make sure your product has the correct number of carbons.]

(b)

Calculate K_eq for the following acid–base reactions. Which is the best base to use to deprotonate acetylene and make the acetylide anion?

(a) HO^- + H―C ≡ C―H ⇌ ^-C ≡ C―H + H₂O

Suggest an acetylide ion and a carbonyl that might be used to make the following products.

(b) 2,6-dimethylhept-3-yn-2-ol

Explain why ethyne should be alkylated before, rather than after, nucleophilic addition.

What is the product of the reaction of an ester with excess acetylide ion followed by the addition of pyridinium chloride?

Show how you might synthesize the following compounds, using acetylene and any ­suitable alkyl halides as your starting materials. If the compound given cannot be ­synthesized by this method, explain why.

a. hex-1-yne

b. hex-2-yne

c. hex-3-yne

Give two sets of reactants (each set including an alkyl halide and a nucleophile) that could be used to synthesize the following alkyne:

CH₃CH₂C≡CCH₂CH₂CH₂CH₃