Chemistry Hydrocarbons SET 2019
PMDC Verified Question 23 of 65
In Friedal Craft's Chlorination of Benzene, Iron III chloride acts as a catalyst, which is the initial reaction in the generation of an electrophile?
A
\( \text{Cl}_2 + \text{FeCl}_3 \rightarrow \text{Cl}^- + \text{FeCl}_4^+ \)
B
\( \text{Cl}_2 + \text{FeCl}_3 \rightarrow 2\text{Cl}^+ + \text{FeCl}_2^- \)
C
\( \text{Cl}_2 + \text{FeCl}_3 \rightarrow \text{Cl}^- + \text{FeCl}_3^+ \)
D
\( \text{Cl}_2 + \text{FeCl}_3 \rightarrow \text{Cl}^+ + \text{FeCl}_4^- \)
Tap any option to test your recall and reveal the step-by-step Propolis autopsy.

Propolis Cognitive Error Autopsy

Official Correct Choice:
Option D: \( \text{Cl}_2 + \text{FeCl}_3 \rightarrow \text{Cl}^+ + \text{FeCl}_4^- \)
Concept:

Lewis acid catalysts facilitate electrophilic aromatic substitution by polarizing and breaking the halogen-halogen bond to create a strong electrophile.

Solution:

  • Iron(III) chloride (\( \text{FeCl}_3 \)) is an electron-deficient Lewis acid with empty d-orbitals.


  • It accepts a pair of electrons from one of the chlorine atoms in \( \text{Cl}_2 \).


  • This causes the Cl-Cl bond to break heterolytically. The chlorine atom attached to Fe leaves with the bonding electrons to form the complex anion \( \text{FeCl}_4^- \).


  • The other chlorine is left deficient in electrons, forming the essential electrophile, \( \text{Cl}^+ \).


  • The precise balanced generation equation is: \( \text{Cl}_2 + \text{FeCl}_3 \rightarrow \text{Cl}^+ + \text{FeCl}_4^- \).


Why other options are incorrect:

  • Equations proposing the formation of \( \text{Cl}^- \) alongside a positively charged Iron complex violate the fundamental behavior of Lewis acids, which accept (not donate) electron pairs to become negatively charged complexes.

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 Hydrocarbons 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