9. Alkenes and Alkynes

How much more stable is the most stable staggered conformer than the most stable eclipsed conformer?

Show how you would synthesize the following compounds, starting with acetylene and any compounds containing no more than four carbon atoms.

d. trans-hex-2-ene

e. 1,1-dibromohexane

f. 2,2-dibromohexane

Show how you would synthesize the following compounds, starting with acetylene and any compounds containing no more than four carbon atoms.

a. hex-1-yne

b. hex-2-yne

c. cis-hex-2-ene

Solved Problem 9-1 showed the synthesis of dec-3-yne by adding the hexyl group first, then the ethyl group. Show the reagents and intermediates involved in the other order of synthesis of dec-3-yne, by adding the ethyl group first and the hexyl group last.

Acetylide alkylation, from Assessment 12.61, fails to give the desired product with 2° haloalkanes. Why? What is the actual product of this reaction?

The intended S_N2 displacement of the 1° chloride by acetylide is unsuccessful for the molecule below. Why?

Show how the following compounds can be synthesized starting with ethyne:

b. trans-3-heptene

Show how each of the following compounds can be synthesized from the given starting materials:

a. CH₃CH₂CH₂Br→CH₃CH₂CH₂CH₂CH₃

How can the following compounds be prepared using ethyne as the starting material?

b.

How could the following compounds be synthesized from acetylene?

c. CH₃CH═CH₂

How could the following compounds be synthesized from acetylene?

d.

How could the following compounds be synthesized from acetylene?

e.

The fragrance of (Z)-1-phenylhex-2-en-1-ol resembles that of roses, with a delicate citrus edge. Show how you would synthesize this compound from benzaldehyde (PhCHO) and any other reagents you need.

Show how you would convert

d. but-1-yne to cis-hex-3-ene.

Show how you would synthesize the following compounds from acetylene and any other needed reagents:

(a) 6-phenylhex-1-en-4-yne

(b) cis-1-phenylpent-2-ene