Chapter 9.11, Problem 13P

Interpretation Introduction

Interpretation:

Using acetylene and other necessary organic and inorganic reagents, the preparation of $\text{2-octanone}$ and $\text{4-octanone}$ is to be shownby using a series of equation.

Concept Introduction:

Alkylation of acetylene takes place in two steps. Acetylene has two acidic protons which can be abstracted by a strong base.

In the first step, the acetylene is treated with sodium amide to convert the acetylene to its conjugate base.

The acetylide ion reacts with an alkyl halide in the second step, forming a new carbon-carbon bond. The halide ion is displaced by an ${\text{S}}_{\text{N}}\text{2}$ type of reaction.

This sequence converts acetylene to its monosubstituted derivative which is also a terminal alkyne.

Repeating this sequence of steps using a different alkyl halide converts acetylene to its disubstituted derivative. The triple bond is internal in this derivative.

Hydration of alkynes takes place in two steps producing ketone as the final product.

In the first step, addition of water to the triple bond takes place according to Markovnikov's rule. Hydrogen gets attached to the triple bonded carbon atom having more hydrogens attached to it.

This addition produces an enol which changes to ketone by tautomerization.

The overall addition employs $\text{mercury (II) sulfate}$ as a catalyst.