The Question is from neet-chemistry , and it was created by the author Mr. S M HUSSAIN

Question

The Friedel-Crafts acylation of benzene with $CH_3COCl$ in the presence of $AlCl_3$ produces acetophenone. Which of the following explains why further acylation is difficult?

Mr. S M HUSSAIN · Accepted Answer

## CORE INFORMATION
✓ **Answer**: B
## CONCEPT FRAMEWORK
	**Primary Concept**: Friedel-Crafts Acylation and Deactivation of Aromatic Rings
	**Related Topics**: Electrophilic Aromatic Substitution, Aromatic Ring Reactivity, Directing Effects of Substituents
	**Prerequisites**: Understanding of electrophilic aromatic substitution, the mechanism of Friedel-Crafts acylation, and the electronic effects of substituents on aromatic rings.
## SOLUTION PATHWAY
**Given Information**:
		Reaction: Benzene + $CH_3COCl$ (in presence of $AlCl_3$) ightarrow Acetophenone
		Question: Why is further acylation difficult?
**Method & Steps**:
	1. Analyze the product: Acetophenone ($C_6H_5COCH_3$) has an acyl group ($-COCH_3$) attached to the benzene ring.
		Reasoning: Acyl groups are deactivating groups in electrophilic aromatic substitution.
		Formula/Rule:  Acyl groups are electron-withdrawing groups due to resonance effects. This reduces the electron density in the benzene ring, making it less reactive towards further electrophilic attack.
	2. Consider the effect of the acyl group:
		Working: The acyl group (-COCH3) is a meta-directing and deactivating group. This means it makes the ring less reactive toward further electrophilic substitution.
		Key Point:  The electron-withdrawing nature of the acyl group reduces the nucleophilicity of the benzene ring, making it less susceptible to further electrophilic attack by another acyl chloride.
	3. Evaluate other options:
		Result: Option B correctly explains the difficulty of further acylation. Options A, C, and D are incorrect because the catalyst deactivation is usually not the primary reason, steric hindrance is relatively minor in this case, and the reaction remains thermodynamically favorable but kinetically slow due to the decreased reactivity of the ring.
		Verification: The deactivation of the benzene ring by the already present acyl group is the main reason why further acylation is difficult.
## OPTION ANALYSIS
A :x: $AlCl_3$ is regenerated during the reaction and is not permanently deactivated. 
B ✓: The acyl group is electron-withdrawing, deactivating the ring towards further electrophilic substitution. This is the primary reason for the difficulty in further acylation.
C :x: While steric hindrance might play a minor role, it's not the primary reason for the reduced reactivity.
D :x: The reaction remains thermodynamically favorable, but the kinetic barrier is significantly increased due to the deactivated ring.
## LEARNING AIDS
	**Common Mistakes**:
		1.Confusing activating and deactivating groups: Remember that acyl groups are deactivating.
		2.Overlooking resonance effects:  Understand how the acyl group withdraws electron density from the ring via resonance.
	**Quick Tips**:
		1.Remember the activating/deactivating and ortho/para/meta directing effects of common substituents.
		2.Draw resonance structures to visualize the electron-withdrawing effect of the acyl group.

Mr. S M HUSSAIN · Answer

The $AlCl_3$ catalyst gets deactivated.

Mr. S M HUSSAIN · Answer

The correct Option is "The acyl group deactivates the ring towards further electrophilic substitution."

Mr. S M HUSSAIN · Answer

Acetophenone is sterically hindered.

Mr. S M HUSSAIN · Answer

The reaction becomes thermodynamically unfavorable.

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