Question

How will you bring about the following conversions:

Ethanol To But-1-yne

Answer 1

Ethanol to But-1-yne:

Step 1 Formation of Ethyl chloride:

Ethanol is treated with Thionyl chloride in presence of pyridine to form Chloroethane, Sulphur dioxide, and Hydrochloric acid. $\underset{\mathrm{Ethanol}}{\mathrm{C}{\mathrm{H}}_3-\mathrm{C}{\mathrm{H}}_2-\mathrm{OH}}+\underset{\mathrm{Thionyl}\mathrm{chloride}}{\mathrm{SOC}{\mathrm{l}}_2}\stackrel{\mathrm{Pyridine}}{\to }\underset{\mathrm{Ethyl}\mathrm{chloride}}{\mathrm{C}{\mathrm{H}}_3-\mathrm{C}{\mathrm{H}}_2-\mathrm{Cl}}+\underset{\mathrm{Sulphur}\mathrm{dioxide}}{\mathrm{S}{\mathrm{O}}_2}+\underset{\mathrm{Hydrochloric}\mathrm{acid}}{\mathrm{HCl}}$

Step 2 Formation of Sodium salt:

Ethyne reacts with Sodium amide in the presents of liquid Ammonia to produce Sodium salt of Ethyne.

$\underset{\mathrm{Ethyne}}{\mathrm{CH}\equiv \mathrm{CH}}+\underset{\mathrm{Sodium}\mathrm{amide}}{\mathrm{NaN}{\mathrm{H}}_2}\stackrel{}{\stackrel{\mathrm{Liq}.{\mathrm{NH}}_3}{\to }}\underset{\mathrm{Sodium}\mathrm{salt}}{\mathrm{CH}\equiv {\mathrm{C}}^{-}\mathrm{N}{\mathrm{a}}^{+}}$

Step 3 Reaction between Sodium salt and Ethyl chloride:

The sodium salt of Ethyne and Ethyl chloride reacts to form But-1-yne.

$\underset{\mathrm{Ethyl}\mathrm{chloride}}{{\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{Cl}}+\underset{\mathrm{Sodium}\mathrm{salt}}{\mathrm{CH}\equiv \mathrm{C}-{\mathrm{Na}}^{+}}\to \underset{\mathrm{But}-1-\mathrm{yne}}{{\mathrm{CH}}_3-{\mathrm{CH}}_2-\mathrm{C}\equiv \mathrm{CH}}+\underset{\mathrm{Sodium}\mathrm{chloride}}{\mathrm{NaCl}}$