Chemistry Carboxylic Acids SET 2019
PMDC Verified Question 60 of 94
Which one of the following compounds can exist in the form of cyclic dimers?
A
Benzene
B
Acetals
C
Ozonide
D
A carboxylic acid
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: A carboxylic acid
Concept:

Carboxylic acids exhibit extraordinarily strong intermolecular hydrogen bonding, causing them to pair up tightly into cyclic dimers, particularly in the vapor phase or in non-polar solvents.

Formula:

$$ (\text{R-COOH})_2 $$

Solution:

  • The highly polarized \( \text{O-H} \) bond of one acid molecule donates a hydrogen bond to the carbonyl oxygen (\( \text{C=O} \)) of a second molecule, and vice-versa.


  • This forms an extremely stable 8-membered cyclic ring structure known as a dimer, doubling their effective molecular weight in certain environments.


Why other options are incorrect:

Benzene is non-polar. Acetals lack hydrogen-bond donors. Ozonides are unstable cyclic intermediates of ozonolysis, not stable hydrogen-bonded dimers.

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