9. Alkenes and Alkynes

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

Predict the product of the following reactions.

(b)

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

b. cis-2-butene.

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

a. pentane.

We have studied a number of pericyclic reactions previously. Draw the mechanism of the steps shown. The section number where this material was first studied is given for your review.

(a)

What alkene would you start with if you wanted to synthesize

b. ethylcyclopentane?

a. How many alkenes could you treat with H₂, Pd/C to prepare methylcyclopentane?

b. Which of the alkenes is the most stable?

c. Which of the alkenes has the smallest heat of hydrogenation?

What reagents would you use for the following syntheses?

a. (Z)-3-hexene from 3-hexyne

What reagents would you use for the following syntheses?

b. (E)-3-hexene from 3-hexyne

Predict the product of the following hydrogenation reactions.

(b)

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

f. cyclodecyne → cis-cyclodecene

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

i. hex-1-yne → hexanal, CH₃(CH₂)₄CHO

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

g. cyclodecyne → trans-cyclodecene

What reagents should be used to carry out the following syntheses?