Haloalkane and Haloarenes part-2 pyQ JEE main 202

Q1. The ascending order of relative rate of solvolysis of the following compounds is: (choose)

 

A.  (C) < (D) < (B) < (A)

B.(D) < (A) < (B) < (C)

C.(D) < (B) < (A) < (C)

D.(C) < (B) < (A) < (D)

Explanation:

Solvolysis (SN1) depends on carbocation stability. Resonance-stabilized benzylic cations are fastest; tertiary or bridged rings next; simple secondary/primary are slower. The correct ascending order (slow → fast) matches the highlighted choice above.

Q2. Assertion (A): SN2 reaction of C₆H₅CH₂Br occurs more readily than SN2 reaction of CH₃CH₂Br.
Reason (R): The partially bonded unhybridized p-orbital that develops in the trigonal bipyramidal transition state is stabilized by conjugation with the phenyl ring.

A

Both (A) and (R) are correct but (R) is not the correct explanation of (A)

B

Both (A) and (R) are correct and (R) is the correct explanation of (A)

C

(A) is not correct but (R) is correct

D

(A) is correct but (R) is not correct

Explanation:

The benzyl substrate stabilizes the SN2 transition state by resonance; the developing positive character is delocalized into the phenyl ring. Hence (A) is true and (R) correctly explains it.

Q3. In the following sequence the major products B and C respectively are: (select)

A

D and F (first pattern)

B

D and F (correct pattern: middle chain shift via Grignard/Swarts)

C

D and F (another arrangement)

D

(Different arrangement)

Explanation:

Na/Et₂O forms the organometallic intermediate (RMgX); subsequent workup (Mg/Et₂O then D₂O or Swarts reaction with CoF₂) yields the observed D and F products (fluorinated chain), matching choice B.

Q4. Assertion (A): Haloalkanes react with KCN to form alkyl cyanides as main product while with AgCN they form isocyanides as main product.
Reason (R): KCN and AgCN both are highly ionic compounds.

A

(A) is correct but (R) is not correct

B

Both (A) and (R) are correct and (R) explains (A)

C

(A) is not correct but (R) is correct

D

(A) is correct but (R) is not correct

Explanation:

KCN dissociates to CN⁻ in solution, which attacks the carbon center giving alkyl cyanide (R–CN). AgCN is more covalent; cyanide is delivered via the carbon–silver bond and nucleophilic attack happens via nitrogen, producing isocyanide (R–NC). So (A) true, (R) false.

Q5. The product (C) in the below-mentioned reaction sequence is:

A. Propan-1-ol

B. Propyne

C. Propan-2-ol

D.Propene

Explanation:

The sequence (dehydrohalogenation → HBr addition → aqueous KOH) yields the secondary alcohol (propan-2-ol) as major product via Markovnikov addition/rearrangement steps. Thus C = propan-2-ol.