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Haloalkanes and Haloarenes appeared 40 times across 3 years — 4.6% of Chemistry. This question is from Stereochemistry and Bond Strength.

Year 2026 2025 2024 Total
Questions 11 16 13 40

Given below are two statements: Statement I : C-Cl bond is stronger in CH₂=CH-Cl than CH₃-CH₂-Cl Statement II : The given optically active molecule,
Optically active alkyl chloride molecule
A chiral tertiary alkyl chloride with Phenyl, Methyl, Ethyl and Chloro groups attached to the central carbon.
on hydrolysis gives a solution that can rotate the plane polarized light. In the light of the above statements, choose the correct answer from the options given below

Solution & Explanation

Core Logic

Statement I: CH₂=CH-Cl is vinyl chloride. The lone pair on chlorine participates in resonance with the adjacent double bond. This imparts a partial double bond character to the C-Cl bond, making it shorter and stronger than the pure single C-Cl bond in CH₃-CH₂-Cl (ethyl chloride).

Resonance in vinyl chloride
A chiral tertiary alkyl chloride with Phenyl, Methyl, Ethyl and Chloro groups attached to the central carbon.
Thus, Statement I is true.

Statement II: The given molecule is a chiral, tertiary alkyl chloride. When it undergoes hydrolysis, it follows an SN1 mechanism because the resulting tertiary carbocation (stabilized by resonance from the phenyl ring and hyperconjugation) is very stable. An SN1 reaction proceeds through a planar carbocation intermediate. Attack by water occurs from both faces with near equal probability, resulting in a racemic mixture.

Resonance in vinyl chloride
A chiral tertiary alkyl chloride with Phenyl, Methyl, Ethyl and Chloro groups attached to the central carbon.
A racemic mixture is optically inactive; it cannot rotate plane-polarized light. Therefore, Statement II is false.

Step 1: Final Conclusion

Statement I is true but Statement II is false.

Pattern Recognition

Vinyl and aryl halides have partial double bond character due to resonance. SN1 at a chiral center leads to racemization (optically inactive product mix).

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes Class 11 Chemistry: Organic Chemistry - Some Basic Principles and Techniques

Reference Study Guides

More Haloalkanes and Haloarenes Previous-Year Questions — Page 8

Q74 jee_main_2024_30_jan_morning Classification
Given below are two statement one is labeled as Assertion (A) and the other is labeled as Reason (R). Assertion (A): CH₂=CH-CH₂-Cl is an example of allyl halide Reason (R): Allyl halides are the compounds in which the halogen atom is attached to sp² hybridised carbon atom. In the light of the two above statements, choose the most appropriate answer from the options given below:
  • A. (A) is true but (R) is false
  • B. Both (A) and (R) are true but (R) is not the correct explanation of (A)
  • C. (A) is false but (R) is true
  • D. Both (A) and (R) are true and (R) is the correct explanation of (A)

Solution

Core Logic

Assertion (A): CH₂=CH-CH₂-Cl is an allyl halide. This statement is True. The halogen is attached to the carbon adjacent to the double bond (allylic position).

Reason (R): Allyl halides are compounds in which the halogen atom is attached to an sp² hybridized carbon atom. This statement is False. In allyl halides, the halogen is attached to an sp³ hybridized carbon atom which is next to an sp² hybridized carbon (C=C double bond).

Step 1: Conclusion

Therefore, (A) is true but (R) is false.

Pattern Recognition

Allylic = sp³ C adjacent to C=C. Vinylic = sp² C of the C=C itself.

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes

Q jee_main_2024_31_jan_evening Nucleophilic Aromatic Substitution
Identify A and B in the following reaction sequence.
Nucleophilic Aromatic Substitution diagram for Q63 - JEE Main 2024 Evening
The image shows a reaction scheme starting from bromobenzene undergoing nitration followed by substitution.
  • A.
  • B.
  • C.
  • D.

Solution

Core Logic
  • When bromobenzene reacts with concentrated HNO₃ (nitration), the bromine atom is ortho/para directing. However, under drastic conditions with excess concentrated nitrating mixture, 1-bromo-2,4,6-trinitrobenzene is formed (Compound A).
  • When 1-bromo-2,4,6-trinitrobenzene (Compound A) is treated with NaOH, the presence of three strong electron-withdrawing -NO₂ groups activates the aromatic ring toward Nucleophilic Aromatic Substitution (SNAr). The -Br is easily replaced by -OH to form 2,4,6-trinitrophenol (picric acid).
  • Subsequent acidification with HCl yields the neutral picric acid (Compound B).
  • Nucleophilic Aromatic Substitution diagram for Q63 - JEE Main 2024 Evening
    The image shows a reaction scheme starting from bromobenzene undergoing nitration followed by substitution.

Pattern Recognition

Multiple NO₂ groups drastically increase the susceptibility of halobenzenes to SNAr. Bromine is replaced completely by OH^- under alkaline conditions.

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes Class 12 Chemistry: Alcohols, Phenols and Ethers

Q jee_main_2024_31_jan_evening IUPAC Nomenclature of Haloalkanes
Identify structure of 2,3-dibromo-1-phenylpentane.
  • A.
  • B.
  • C.
  • D.

Solution

Core Logic

Decode the IUPAC name: 2,3-dibromo-1-phenylpentane.

  • Parent chain is pentane (5 carbon chain: C1-C2-C3-C4-C5).
  • Substituents:
  • Phenyl group at position 1.
  • Bromo groups at positions 2 and 3.
  • Option (3) correctly displays a 5-carbon straight chain. The first carbon attaches to the benzene ring (phenyl group), and the second and third carbons each hold a bromine atom.

    IUPAC Nomenclature of Haloalkanes diagram for Q67 - JEE Main 2024 Evening
    IUPAC Nomenclature of Haloalkanes diagram for Q67 - JEE Main 2024 Evening

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes

Q jee_main_2024_31_jan_morning Elimination and Addition Reactions
The product (C) in the below mentioned reaction is: CH₃-CH₂-CH₂-Br [Δ]KOH(alc) A [Δ]HBr B [Δ]KOH(aq) C
  • A. Propan-1-ol
  • B. Propene
  • C. Propyne
  • D. Propan-2-ol

Solution

Step 1: Elimination to form Propene
CH₃-CH₂-CH₂-Br KOH (alc), Δ CH₃-CH=CH₂ (Compound A: Propene)
Step 2: Electrophilic Addition of HBr

Addition of HBr follows Markovnikov's rule:

CH₃-CH=CH₂ + HBr Δ CH₃-CH(Br)-CH₃ (Compound B: 2-Bromopropane)
Step 3: Nucleophilic Substitution

Reaction with aqueous KOH leads to SN2/SN1 substitution of Br^- with OH^-:

CH₃-CH(Br)-CH₃ KOH (aq), Δ CH₃-CH(OH)-CH₃ (Compound C: Propan-2-ol)
Pattern Recognition

Alc. KOH gives elimination (alkene). Aq. KOH gives substitution (alcohol). HBr on unsymmetrical alkene gives Markovnikov addition.

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes

Q86 jee_main_2024_31_jan_morning Elimination and Substitution
CH₃CH₂Br + NaOH arrow Product A CH₃CH₂Br + NaOH / H₂O arrow Product B The total number of hydrogen atoms in product A and product B is
Numerical Answer. Answer: 10 to 10

Solution

Core Logic

Reaction 1: If the reagent is alcoholic NaOH (implied due to formation of a distinct product A to contrast B), elimination occurs:

CH₃CH₂Br + NaOH (alc) arrow CH₂=CH₂ (Ethene)

Hydrogen atoms in ethene (C₂H₄) = 4.

Reaction 2: If the reagent is aqueous NaOH (NaOH / H₂O), nucleophilic substitution (SN2) occurs:

CH₃CH₂Br + NaOH (aq) arrow CH₃CH₂OH (Ethanol)

Hydrogen atoms in ethanol (C₂H₆O) = 6.

Total hydrogen atoms = 4 + 6 = 10.

Chapter Mix

Class 12 Chemistry: Haloalkanes and Haloarenes

More Haloalkanes and Haloarenes Questions — jee_main_2026_24_january_morning

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