Chemistry Fundamental Principles of Organic Chemistry MDCAT 2015
PMDC Verified Question 77 of 83
The structural formula of 2,3,4-trimethylpentane is:
A
\( \text{H}_3\text{C--CH}(\text{CH}_3)\text{--CH}(\text{CH}_3)\text{--CH}(\text{CH}_3)\text{--CH}_3 \)
B
\( \text{H}_3\text{C--CH}_2\text{--C}(\text{CH}_3)_2\text{--CH}_2\text{--CH}_3 \)
C
\( \text{H}_3\text{C--C}(\text{CH}_3)_2\text{--CH}_2\text{--CH}_3 \)
D
\( \text{CH}_3\text{--CH}_2\text{--CH}(\text{CH}_3)\text{--C}(\text{CH}_3)_3 \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option A: \( \text{H}_3\text{C--CH}(\text{CH}_3)\text{--CH}(\text{CH}_3)\text{--CH}(\text{CH}_3)\text{--CH}_3 \)
Concept:

To write the structural formula from an IUPAC name, first identify the parent chain, then place substituents at the specified carbon numbers.

Solution:

  • Parent chain: "pentane" indicates a 5-carbon continuous chain (\( \text{C--C--C--C--C} \)).


  • Substituents: "2,3,4-trimethyl" indicates three separate methyl (\( \text{-CH}_3 \)) groups attached to carbons 2, 3, and 4.


  • Adding the correct number of hydrogens gives: \( \text{CH}_3\text{--CH}(\text{CH}_3)\text{--CH}(\text{CH}_3)\text{--CH}(\text{CH}_3)\text{--CH}_3 \).


  • This matches Option A.


Why other options are incorrect:

Option B is 3,3-dimethylpentane. Option C is 2,2-dimethylbutane. Option D represents a different heavily branched isomer.

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.

Previous Question All Fundamental Principles of Organic Chemistry MCQs Next Question

Want to solve full-length papers under timed exam conditions?

Practice with zero-scroll lockdown sprints, dynamic latency zone timers, live peer selection telemetry, and the automated Amber mistake recovery loop.

Enter Arena Sprint iOS App Android App