Chemistry Carboxylic Acids DUHS 2023
PMDC Verified Question 34 of 94
What's the IUPAC name of \( \alpha \), \( \beta \)-dimethyl valeric acid?
A
2,3-dimethyl hexanoic acid
B
3,4-dimethyl hexanoic acid
C
3,4-dimethyl pentanoic acid
D
2,3-dimethyl pentanoic 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: 2,3-dimethyl pentanoic acid
Concept:

Translating common Greek-letter nomenclature to IUPAC requires knowing the parent chain length and how alpha/beta positions map to numeric locants.

Solution:

  • Parent Chain: Valeric acid has 5 carbon atoms. In IUPAC, a 5-carbon acid is pentanoic acid.


  • Numbering: In IUPAC, the carbonyl carbon is C1. Therefore, the adjacent \( \alpha \)-carbon is C2, and the \( \beta \)-carbon is C3.


  • Substituents: There are methyl groups at the \( \alpha \) (C2) and \( \beta \) (C3) positions.


  • Combining these gives: 2,3-dimethylpentanoic acid.


Why other options are incorrect:

Hexanoic acid indicates a 6-carbon parent chain (caproic acid, not valeric). Option C uses incorrect locants (3,4 instead of 2,3).

Quality & Fidelity Assurance: Every question on BeambePrep is rigorously curated against the official PMDC syllabus with zero filler, zero out-of-syllabus content, and zero typos. When an authentic past paper originally contained a historical mistake or ambiguity from the examining board (such as UHS or NUMS), BeambePrep faithfully reflects the original paper while detailing the nuance and scientific consensus in the autopsy above.

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