Chapter 9, Problem 34P

Interpretation Introduction

Interpretation:

Using acetylene and other necessary organic and inorganic reagents, the synthesis of $2-\text{heptanone}$ is to be described.

Concept Introduction:

>

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

>

The acetylene is treated with sodium amide to convert the acetylene to its conjugate base in the second step.

>

The acetylide ion reacts with an alkyl halide in the first step forming a new carbon-carbon bond. The halide ion is displaced by ${\text{S}}_{\text{N}}\text{2}$ 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 the 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 reaction produces an enol which changes to ketone by tautomerization.

>

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