When chlorobenzene is subjected to aggressive free-radical chlorination conditions ( gas at very high temperatures or intense UV light), typical substitution of the aryl hydrogens does not occur. Whic

Question

When chlorobenzene is subjected to aggressive free-radical chlorination conditions ($Cl_2$ gas at very high temperatures or intense UV light), typical substitution of the aryl hydrogens does not occur. Which of the following statements accurately describe the chemical realities of this system?

Prashant Kotian · Accepted Answer

Correct answer: A,C,D. A) True. Aryl bonds are very strong ( kcal/mol). B) False. The effect requires parallel p-orbitals. The aryl radical would reside in an orthogonal orbital, so it cannot interact with the pi-system or the chlorine lone pairs via resonance. C) True. Extreme UV conditions can force chlorine radicals to add across the pi-bonds, breaking aromaticity to form products similar to BHC (Benzene Hexachloride). D) True. Direct halogenation of arenes relies on electrophilic aromatic substitution (EAS), requiring heterolytic cleavage of via a Lewis acid.

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