Chapter U2.7, Problem 3E

Interpretation Introduction

Interpretation: The reason for the disappearance of the foul smell of butyric acid on mixing with methanol and heating the mixture needs to be explained.

Concept Introduction: The reaction which results in the formation of at least one ester along with water on heating acids with alcohol in presence of an acid catalyst is said to be esterification.

Answer to Problem 3E

The foul smell of butyric acid disappeared on mixing with methanol and heating the mixture due to the formation of an ester, methyl butanoate which has a sweet smell.

Explanation of Solution

The general reaction for the esterification is written as:

  $\begin{array}{l}\text{RCOOH}{\text{+R}}^{\text{'}}\text{OH}\stackrel{\text{Δ}}{\to }{\text{RCOOR}}^{\text{'}}\text{+}{\text{H}}_{\text{2}}\text{O}\\ \text{Acid}\text{Alcohol}\text{Ester}\text{water}\end{array}$

Thus, the reaction between methanol and butyric acid is:

  

The mechanism for the reaction is:

  

Thus, the foul smell of butyric acid disappeared on mixing with methanol and heating the mixture due to the formation of ester, methyl butanoate which has a sweet smell.