Chemistry Carboxylic Acids MDCAT 2013
PMDC Verified Question 84 of 94
The formation of ester from acetic acid in presence of acid and ethanol is a:
A
Nucleophilic addition reaction
B
Nucleophilic substitution reaction
C
Electrophilic substitution reaction
D
Electrophilic addition reaction
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Nucleophilic substitution reaction
Concept:

Esterification is formally classified as a Nucleophilic Acyl Substitution reaction.

Formula:

$$ \text{RCOOH} + \text{R}'\text{OH} \rightleftharpoons^+} \text{RCOOR}' + \text{H}_2\text{O} $$

Solution:

  • In Fischer esterification, the oxygen atom of the alcohol acts as a nucleophile.


  • It attacks the electron-deficient carbonyl carbon of the protonated carboxylic acid.


  • Following proton transfers, a water molecule is eliminated (acts as a leaving group), completely substituting the original \(-\text{OH}\) group of the acid with the \(-\text{OR}'\) group.


Why other options are incorrect:

It is not a pure addition because a leaving group (water) is expelled. Electrophiles do not attack the carbon skeleton in this mechanism.

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