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Question #44166

Difficulty: 8/10 | 🟢 Free

The Question

Consider the following compounds in the gas phase at $298\text{ K}$ : (I) \ce{o-Dichlorobenzene} (II) \ce{Cyclohexyl chloride} (III) \ce{Chlorobenzene} (IV) \ce{Fluorobenzene}

Which of the following represents the correct decreasing order of their net dipole moments?

Options

A.
$\text{I} > \text{II} > \text{III} > \text{IV}$
B.
$\text{I} > \text{II} > \text{IV} > \text{III}$
C.
$\text{II} > \text{I} > \text{III} > \text{IV}$
D.
$\text{I} > \text{IV} > \text{III} > \text{II}$

Check Your Answer

Correct Answer

Step-by-Step Solution

Explanation

How the Examiner Thinks

Mechanism_Trap

Don't get tricked by the process! Learn the mechanical traps used in competitive exam questions.

Concepts Behind This Question

Dipole Moment Vector Addition|Electrophilic Substitution Activation/Deactivation|Inductive Effect Trends

Why This Question Is Tricky

Common Mistakes

This question tests the 'Lone Pair Delocalization vs Inductive Effect' trap in the context of dipole moment vector addition.

Students often rely on the rote rule that 'higher electronegativity equals higher dipole moment', leading them to incorrectly predict that Fluorobenzene is more polar than Chlorobenzene.

They fail to account for the opposing $+M$ (mesomeric) vector, which is significantly stronger in Fluorobenzene due to highly effective $2p-2p$ orbital overlap compared to the $3p-2p$ overlap in Chlorobenzene.

Additionally, comparing the $sp^3$ hybridized Cyclohexyl chloride with the $sp^2$ hybridized Chlorobenzene highlights the absence of this opposing resonance vector in saturated systems, making the alkyl halide more polar than the aryl halide.

Finally, vector addition in o-Dichlorobenzene confirms the understanding of molecular geometry.

Quick Facts About This Question

Question Information

Subject	Chemistry
Chapter	Chemical Bonding and Molecular Structure - Class 11 Part 1
Concept	Dipole Moment Vector Addition
Difficulty	8
Cognitive Load	7
Target Solve Time	160 sec
Access	Free