Haloalkanes and Haloarenes NEET Previous Year Questions (PYQs)
Practice NEET previous year questions from Haloalkanes and Haloarenes. These MCQs cover reaction mechanisms, stereochemistry, and reactivity with answers and clear explanations.
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Haloalkanes & Haloarenes Chapter Notes
Q1. The hydrolysis reaction that takes place at the slowest rate is:
(NEET Odisha 2019)
- (A) Ethyl bromide
- (B) Isopropyl bromide
- (C) tert-Butyl bromide
- (D) Chlorobenzene
Show Answer
(D)
Show Explanation
In chlorobenzene, the C–Cl bond has partial double bond character due to resonance, making nucleophilic substitution very difficult.
Q2. Which solvent favours SN2 reaction the most?
(NEET 2016)
- (A) Water
- (B) Methanol
- (C) Ethanol
- (D) Dimethylformamide (DMF)
Show Answer
(D)
Show Explanation
Polar aprotic solvents like DMF favour SN2 reactions by stabilising ions without solvating nucleophiles.
Q3. Which of the following biphenyls is optically active?
(NEET 2016)
- (A) Unsubstituted biphenyl
- (B) Ortho-disubstituted biphenyl
- (C) Para-disubstituted biphenyl
- (D) Meta-disubstituted biphenyl
Show Answer
(B)
Show Explanation
Ortho-disubstituted biphenyls are non-planar and lack symmetry, making them optically active.
Q4. The major product in dehydrohalogenation of 2-bromopentane is pent-2-ene. This follows:
(NEET 2023)
- (A) Hofmann rule
- (B) Hund’s rule
- (C) Huckel rule
- (D) Saytzeff rule
Show Answer
(D)
Show Explanation
According to Saytzeff rule, the more substituted alkene is the major product.
Q5. Which alkyl halide undergoes SN1 reaction most readily?
(NEET 2020)
- (A) Ethyl chloride
- (B) Isopropyl chloride
- (C) tert-Butyl chloride
- (D) Methyl chloride
Show Answer
(C)
Show Explanation
SN1 reaction rate depends on carbocation stability; tertiary carbocations are most stable.
Q6. Which compound undergoes racemisation during hydrolysis with aqueous KOH?
(NEET 2014)
- (A) Primary haloalkane
- (B) Secondary haloalkane
- (C) Tertiary haloalkane
- (D) Chiral secondary haloalkane
Show Answer
(D)
Show Explanation
Racemisation occurs via planar carbocation intermediate in SN1 reaction at a chiral centre.
Q7. Which of the following reactions proceeds via elimination–addition mechanism?
(NEET 2017)
- (A) Chlorobenzene + NaOH
- (B) Ethyl chloride + KOH
- (C) tert-Butyl bromide + water
- (D) Benzyl chloride + KOH
Show Answer
(A)
Show Explanation
Nucleophilic substitution in aryl halides occurs via elimination–addition mechanism.
Q8. Which compound will undergo SN2 reaction fastest?
(NEET 2008)
- (A) tert-Butyl bromide
- (B) Isopropyl bromide
- (C) Ethyl bromide
- (D) Neopentyl bromide
Show Answer
(C)
Show Explanation
SN2 reactions are fastest with primary alkyl halides having least steric hindrance.
Q9. Which halide is least reactive towards nucleophilic substitution?
(NEET 2004)
- (A) Benzyl chloride
- (B) Allyl chloride
- (C) Vinyl chloride
- (D) tert-Butyl chloride
Show Answer
(C)
Show Explanation
In vinyl chloride, the C–Cl bond has partial double bond character due to conjugation.
Q10. Which of the following is optically active?
(NEET 1989)
- (A) 1-Butanol
- (B) 1-Propanol
- (C) 2-Chlorobutane
- (D) 2-Propanol
Show Answer
(C)
Show Explanation
2-Chlorobutane has a chiral carbon atom attached to four different groups.
Q11. Reaction of tert-butyl bromide with sodium methoxide mainly gives:
(NEET 1994)
- (A) tert-Butyl alcohol
- (B) tert-Butyl methyl ether
- (C) Isobutylene
- (D) Isobutane
Show Answer
(C)
Show Explanation
Strong base and tertiary substrate favour elimination (E2), forming isobutylene.
Q12. Grignard reagent is prepared by reaction between:
(NEET 1994)
- (A) Zn + alkyl halide
- (B) Mg + alkane
- (C) Mg + alkyl halide
- (D) Na + alkyl halide
Show Answer
(C)
Show Explanation
Grignard reagents are prepared by reacting alkyl halides with magnesium in dry ether.
Q13. Benzene reacts with propyl chloride in presence of anhydrous AlCl3 to give:
(NEET 1993)
- (A) n-Propylbenzene
- (B) Isopropylbenzene
- (C) Chlorobenzene
- (D) No reaction
Show Answer
(B)
Show Explanation
Carbocation rearrangement occurs, forming more stable isopropyl carbocation.
Q14. Phosgene is chemically known as:
(NEET 1988)
- (A) Carbonyl chloride
- (B) Thionyl chloride
- (C) Phosphoryl chloride
- (D) Carbon dioxide
Show Answer
(A)
Show Explanation
Phosgene has the formula COCl2 and is called carbonyl chloride.
Q15. Which reaction is nucleophilic substitution?
(NEET 2009)
- (A) Addition of Br2 to alkene
- (B) Hydrolysis of alkyl halide
- (C) Nitration of benzene
- (D) Hydrogenation
Show Answer
(B)
Show Explanation
In hydrolysis, OH⁻ replaces halide ion, which is a nucleophilic substitution.
Q16. Which alkyl halide gives only one monochloro derivative?
(NEET 2001)
- (A) n-Butane
- (B) Isobutane
- (C) Neopentane
- (D) Isopentane
Show Answer
(C)
Show Explanation
All hydrogen atoms in neopentane are equivalent.
Q17. Which compound is NOT chiral?
(NEET 2006)
- (A) 2-Butanol
- (B) 2,3-Dibromopentane
- (C) 3-Bromopentane
- (D) Lactic acid
Show Answer
(C)
Show Explanation
3-Bromopentane does not have a carbon attached to four different groups.
Q18. Which compound undergoes nucleophilic substitution exclusively by SN1 mechanism?
(NEET 2005)
- (A) Ethyl chloride
- (B) Isopropyl chloride
- (C) Benzyl chloride
- (D) Chlorobenzene
Show Answer
(C)
Show Explanation
Benzyl carbocation is resonance-stabilised, favouring SN1 reaction.
Q19. Reactivity order of halides in dehydrohalogenation is:
(NEET 2002)
- (A) R–F > R–Cl > R–Br > R–I
- (B) R–I > R–Br > R–Cl > R–F
- (C) R–Cl > R–Br > R–I > R–F
- (D) R–Br > R–Cl > R–I > R–F
Show Answer
(B)
Show Explanation
C–I bond is weakest and breaks most easily during elimination.
Q20. Replacement of chlorine in 2,4-dinitrochlorobenzene occurs easily because:
(NEET 1997)
- (A) –NO2 groups donate electrons
- (B) –NO2 groups withdraw electrons
- (C) Ring becomes electron rich
- (D) Chlorine becomes more electronegative
Show Answer
(B)
Show Explanation
Electron-withdrawing –NO2 groups stabilise the intermediate, facilitating substitution.
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