9. Alkenes and Alkynes

Predict the product of the following hydrogenation reactions.

(c)

The following deprotonation step occurs during the trans reduction of an alkyne. Calculate K_eq for this reaction.

Sodium amide, the base we use to deprotonate terminal alkynes, is synthesized by reducing ammonia via a mechanism similar to the reduction of alkynes in Figure 10.21. Suggest a mechanism for this reaction.

Reduction of an alkyne using the Lindlar catalyst, a reaction presented in Section 10.6.2, produces only the cis-alkene. Why?

Identify the product when each of the following reactions is performed on the triglyceride of linoleic acid (linoleate).

(a) H₂ , Pd

Hydrogenation of which alkynes would produce the following cis-alkenes?

(b)

What is the major product of the reaction of 1 mol of propyne with each of the following reagents?

g. excess H₂, Pd/C

h. H₂/Lindlar catalyst

Describe the alkyne you should start with and the reagents you should use if you want to synthesize

c. trans-2-pentene.

d. 1-hexene.

What reagents would you use for the following syntheses?

c. hexane from 3-hexyne

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

e.

Show how each of the following compounds can be prepared using the given starting material, any needed inorganic reagents, and any ­organic compound that has no more than four carbons:

f.

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

f.

Show how you would convert

c. cis-cyclodecene to trans-cyclodecene.

What reaction would acetylene likely undergo if it were kept at 1500°C for too long?

Hydration of alkynes (via oxymercuration) gives good yields of single compounds only with symmetrical or terminal alkynes. Show what the products would be from hydration of each compound.

d. cyclodecyne