Chemistry Alkyl Halides UHS 2024
PMDC Verified Question 2 of 13
Identify the correct statement related to substitution and elimination of alkyl halides:
A
Strong bases cause substitution in preference to elimination
B
Role of leaving groups in elimination is similar to substitution
C
Substitution is favoured more than elimination by decreasing solvent polarity
D
Decrease in temperature will favor elimination more than substitution
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option B: Role of leaving groups in elimination is similar to substitution
Concept:

Substitution and elimination are competing pathways that share fundamental kinetic requirements, such as the need for the leaving group to detach.

Solution:

  • In both substitution (\( S_N1 / S_N2 \)) and elimination (\( E_1 / E_2 \)), the carbon-halogen bond must break, and the halide ion must depart with the electron pair.
  • Therefore, a good leaving group (like \( I^- \)) accelerates both reaction types equally. The role and requirement of the leaving group are identical across both mechanisms.


Why other options are incorrect:

  • Option A: Strong bases heavily favor elimination (by abstracting a proton) over substitution.
  • Option C: Decreasing solvent polarity favors elimination (e.g., alcoholic KOH vs aqueous KOH).
  • Option D: Elimination reactions have higher activation energies and are entropically favored (creating more product molecules), so an increase in temperature favors elimination, not a decrease.

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 Alkyl Halides 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