Question

A compound $X$ (having a vinegar-like smell) when treated with ethanol in the presence of acid $z$, gives a compound $y$, which has a fruity smell. The reaction is:

$C_2{H}_{5}OH+X\stackrel{Z}{\to }Y+H_{2}O$
(i) Identify$Y$and $Z$
(ii) Write the structural formula of$X$
(iii) Name the above reaction

Answer 1

(i) Since $X$ has a vinegar-like smell, it must be acidic. When acids react with alcohols, they produce esters, which means, $Y$must be an ester. This reaction is done in the presence of sulphuric acid, hence, $Z$must be sulphuric acid ($H_{2}S{O}_4$ ).
$C_2{H}_{5}OH+X\stackrel{Z}{\to }Y+H_{2}O$
Ethanol Acid Ester
(ii) Since, this is an esterification reaction,$X$ must be an Acid. Since it has a vinegar-like smell, and upon reaction with Ethanol, it gives a fruity-smelling compound, it must be Ethanoic Acid. The structure is$-CH3COOH$. This is also known as Acetic acid.
(iii) When alcohol reacts with a vinegar-like smelling compound and produces a fruity smelling compound, in the presence of Sulphuric acid ( $H_{2}S{O}_4$ ), the reaction is called the Esterification reaction. It is as follows:
$C{H}_{3}COOH+C_2{H}_{5}OH+H^{+}\to C{H}_{3}COO{C}_2{H}_5+H_{2}O$
Acetic acid Ethanol Ethyl ethanoate
Sulphuric acid acts as a catalyst in this reaction by protonation of the acid thus making it a better electrophile for the attack of the alcohol.