Chapter 7, Problem 51P

(a)

Interpretation Introduction

Interpretation:

The reason for obtaining a single pure product from hydroboration-oxidation of 2-butyne and two products from hydroboration-oxidation of 2-pentyne should be determined.

Concept Introduction:

Hydroboration-oxidation reaction:

• Internal alkynes oxidize to form ketones.
• Terminal alkyne oxidize to form aldehyde.
• Reagents used are ${\text{BH}}_{\text{3}}\text{and}{\text{R}}_{\text{2}}\text{BH}$ for internal alkyne.
• ${\text{R}}_{\text{2}}\text{BH}$ is the reagent used for terminal alkynes.

General mechanism for hydroboration oxidation:

(b)

Interpretation Introduction

Interpretation:

The name of other two internal alkynes which yield only one product upon hydroboration-oxidation reaction has to be determined.

Concept Introduction:

Hydroboration-oxidation reaction:

• Internal alkynes oxidize to form ketones.
• Terminal alkyne oxidize to form aldehyde.
• Reagents used are ${\text{BH}}_{\text{3}}\text{and}{\text{R}}_{\text{2}}\text{BH}$ for internal alkyne.
• ${\text{R}}_{\text{2}}\text{BH}$ is the reagent used for terminal alkynes.

General mechanism for hydroboration oxidation: