Chemistry Carboxylic Acids BUMHS 2024
PMDC Verified Question 16 of 94
On heating acetic acid in the presence of \( \text{P}_2\text{O}_5 \), dehydration occurs with the formation of
A
Acetamide
B
Octyl acetate
C
Methyl acetate
D
Acetic anhydride
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: Acetic anhydride
Concept:

Phosphorus pentoxide (\( \text{P}_2\text{O}_5 \)) is a hyper-aggressive dehydrating agent capable of ripping a water molecule out from between two carboxylic acid molecules.

Formula:

$$ 2\text{CH}_3\text{COOH} \xrightarrow{\text{P}_2\text{O}_5, \Delta} \text{CH}_3\text{-CO-O-CO-CH}_3 + \text{H}_2\text{O} $$

Solution:

  • Two molecules of acetic acid are brought together.


  • \( \text{P}_2\text{O}_5 \) removes an \( -\text{OH} \) from one and an \( -\text{H} \) from the other.


  • The resulting bond fuses the two acyl groups through a central oxygen, forming acetic anhydride.


Why other options are incorrect:

Acetamide requires ammonia. Methyl and octyl acetates are esters, requiring the presence of an alcohol.

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