9. Alkenes and Alkynes

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

a. cis-2-octene

When using sulfuric acid, but in the absence of other nucleophiles like water or bromide ion, less stable alkenes can be isomerized to their more stable isomer. Provide a mechanism for these acid-catalyzed isomerization reactions. [This is one illustration of the principle of microscopic reversibility.]

(c)

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

Muscalure, the sex attractant of the common housefly, is cis-tricos-9-ene. Most syntheses of alkenes give the more stable trans isomer as the major product. Devise a synthesis of muscalure from acetylene and other compounds of your choice. Your synthesis must give specifically the cis isomer of muscalure.

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

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

e. 2,2-dibromohexane → hex-1-yne

How could the following compounds be synthesized from acetylene?

c. CH₃CH═CH₂

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

b.