Chemistry Carboxylic Acids PMC 2021
PMDC Verified Question 51 of 94
Number of oxygen in cyclic ring of dimer of carboxylic acid are:
A
2
B
4
C
5
D
6
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: 4
Concept:

Carboxylic acids (\( \text{R-COOH} \)) readily form dimers through intermolecular hydrogen bonding in the vapor phase and in non-polar solvents.

Solution:

  • A single molecule of a monocarboxylic acid contains 2 oxygen atoms.


  • A dimer is formed by the hydrogen-bonding association of exactly two such acid molecules.


  • Therefore, \( 2 \text{ molecules} \times 2 \text{ oxygen atoms/molecule} = 4 \text{ oxygen atoms} \) in the resulting cyclic dimer structure.


Why other options are incorrect:

The math directly totals to 4. Options A, C, and D are mathematically impossible for a dimer of a standard monocarboxylic acid.

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