Chapter 9.6, Problem 5P

Interpretation Introduction

Interpretation:

Using acetylene and any necessary organic and inorganic reagents, an efficient synthesis for the given alkynes is to be outlined.

Concept Introduction:

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

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

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

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

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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.