Question

Which of the following will give a pleasant smell of ester when heated with ethanol and a small quantity of concentrated sulfuric acid?

• A. ${CH}_{3}COOH$
• B. ${CH}_3{CH}_{2}OH$
• C. ${CH}_{3}OH$
• D. ${CH}_{3}CHO$

Answer 1

The correct option is A

${\mathrm{CH}}_3\mathrm{COOH}$

Explanation for correct option:

(A) Acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$ will produce a pleasant smell of ester when heated with Ethanol $\left({\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\right)$ and small amount of concentrated sulfuric acid $\left({\mathrm{H}}_2{\mathrm{SO}}_4\right)$.

Reaction summary

• The reaction between an alcohol and carboxylic acid in the presence of an acid catalyst is known as esterification.
• When Acetic acid reacts with Ethanol and a small amount of concentrated sulfuric acid, then formation of ester that is Ethyl acetate $\left({\mathrm{CH}}_3{\mathrm{COOC}}_2{\mathrm{H}}_5\right)$ takes place along with a water molecule $\left({\text{H}}_{\text{2}}\text{O}\right)$. Esters have a fruity pleasant smell.

Chemical reaction

• ${\mathrm{CH}}_3\mathrm{COOH}\left(\mathrm{aq}\right)+{\mathrm{C}}_2{\mathrm{H}}_5\mathrm{OH}\left(\mathrm{aq}\right)\to {\mathrm{CH}}_3{\mathrm{COOC}}_2{\mathrm{H}}_5\left(\mathrm{aq}\right)+{\mathrm{H}}_2\mathrm{O}\left(\mathrm{l}\right)$

Explanation for incorrect options:

(B) No chemical reaction occurs when ethanol is heated with ethanol and sulfuric acid.

(C) No chemical reaction occurs when methanol $\left({\mathrm{CH}}_3\mathrm{OH}\right)$ is heated with ethanol and sulfuric acid.

(D) Ethanal $\left({\mathrm{CH}}_3\mathrm{CHO}\right)$ will not give a pleasant smell of ester by its reaction with ethanol and conc. sulfuric acid.

Hence, option (A) is correct. Acetic acid $\left({\mathrm{CH}}_3\mathrm{COOH}\right)$ will give a pleasant smell of ester when heated with ethanol and a small quantity of concentrated sulfuric acid.