CBSE Class 12 Chemistry MCQs on Haloalkanes and Haloarenes

Haloalkanes and Haloarenes are important part of CBSE Class 12 Chemistry Syllabus and they form a strong base for CBSE Class 12 Board Exam. Students often find this chapter slightly confusing due to different types of reactions like substitution, elimination and the effect of halogen atoms on the benzene ring. To make study more effective, solving haloalkanes and haloarenes mcq is one of the best method.

We are going to practice haloalkanes and haloarenes class 12 mcq that are designed as per NCERT Solutions for class 12 chemistry. Practicing these questions not only help in board exams but also improve logical thinking and concept clarity. You will also find mcq of chapter haloalkanes and haloarenes class 12 in many reference books, but here the focus is on simple understanding and exam point of view.

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Haloalkanes and Haloarenes MCQs with Answers and Explanations

Here is a structured set of MCQs with answers and explanations for Class 12 Chemistry – Haloalkanes and Haloarenes. These follow the CBSE Class 12 Chemistry syllabus and align with NCERT Solutions for Class 12 Chemistry.

1. Which of the following is a primary alkyl halide?

a) CH3Cl

b) (CH3)3CCl

c) C6H5Cl

d) CH2=CHCl

Answer: a) CH3Cl

Explanation: In CH3Cl, the carbon bonded to halogen is attached to only one other carbon → primary.

2. Which reagent is used to convert alkyl halides into alcohols?

a) KOH (aq)

b) KOH (alc)

c) Zn/acid

d) Na metal

Answer: a) KOH (aq)

Explanation: Aqueous KOH provides hydroxide ions which replace halogen by OH group → alcohol.

3. Order of reactivity of alkyl halides in SN1 reaction is:

a) 3° > 2° > 1°

b) 1° > 2° > 3°

c) 2° > 3° > 1°

d) 3° > 1° > 2°

Answer: a) 3° > 2° > 1°

Explanation: SN1 depends on carbocation stability. Tertiary carbocations are most stable.

4. Which alkyl halide reacts fastest in SN2 mechanism?

a) CH3Cl

b) C2H5Cl

c) (CH3)3CCl

d) CH3Br

Answer: d) CH3Br

Explanation: SN2 is fastest with least steric hindrance and better leaving group. CH3Br > CH3Cl.

5. The best method to prepare chlorobenzene is:

a) Free radical chlorination

b) Sandmeyer reaction

c) Wurtz reaction

d) Friedel-Crafts reaction

Answer: b) Sandmeyer reaction

Explanation: Sandmeyer: C6H5N2+Cl– + CuCl → C6H5Cl.

6. Which bond is strongest?

a) C–F

b) C–Cl

c) C–Br

d) C–I

Answer: a) C–F

Explanation: Due to high bond enthalpy from small size and high electronegativity of fluorine.

7. Which of the following is an aryl halide?

a) C2H5Br

b) C6H5Cl

c) CH3Cl

d) C3H7I

Answer: b) C6H5Cl

Explanation: Halogen attached directly to aromatic ring is an aryl halide.

8. Why aryl halides do not undergo SN1/SN2 easily?

a) Resonance stabilization

b) High bond strength of C–Cl in aryl halide

c) Partial double bond character

d) All of the above

Answer: d) All of the above

Explanation: Aryl halides resist substitution due to resonance, double bond character, and strong C–X bond.

9. What is major product when chlorobenzene reacts with NaOH at 623 K and 300 atm?

a) Phenol

b) Benzene

c) Chlorophenol

d) Aniline

Answer: a) Phenol

Explanation: High temperature and pressure produce phenol via elimination–addition mechanism.

10. In haloalkanes, the C–X bond is:

a) Ionic

b) Polar covalent

c) Non-polar

d) Metallic

Answer: b) Polar covalent

Explanation: Due to electronegativity difference between carbon and halogen.

11. Which of the following is used as refrigerant (Freon-12)?

a) CCl4

b) C2H5Cl

c) CCl2F2

d) CHCl3

Answer: c) CCl2F2

Explanation: Freon-12 = dichlorodifluoromethane.

12. Which test is used for detection of halogen in organic compounds?

a) Lassaigne’s test

b) Beilstein test

c) Benedict’s test

d) Lucas test

Answer: b) Beilstein test

Explanation: Green flame on copper wire indicates halogen.

13. Which compound shows highest boiling point?

a) CH3Cl

b) CH3Br

c) CH3F

d) CH3I

Answer: d) CH3I

Explanation: Larger molecular mass → higher van der Waals forces → higher boiling point.

14. Which of the following is not an elimination product of C2H5Br with alc. KOH?

a) Ethene

b) Ethane

c) HBr

d) Water

Answer: b) Ethane

Explanation: Dehydrohalogenation gives ethene, not ethane.

15. The IUPAC name of CH2=CH–CH2Cl is:

a) Allyl chloride

b) Prop-2-enyl chloride

c) Vinyl chloride

d) 1-chloroprop-2-ene

Answer: d) 1-chloroprop-2-ene

Explanation: Double bond at 2-position and chlorine at 1-position.

16. Which of the following is used as anesthetic?

a) Chloroform

b) Benzene

c) CCl4

d) Vinyl chloride

Answer: a) Chloroform

Explanation: Chloroform was earlier used as anesthetic but is toxic.

17. Which haloalkane shows fastest hydrolysis in aqueous medium?

a) CH3Cl

b) CH3Br

c) CH3I

d) C6H5Cl

Answer: c) CH3I

Explanation: Iodide is best leaving group.

18. Which reaction is used to prepare alkyl fluorides?

a) Swartz reaction

b) Sandmeyer reaction

c) Wurtz reaction

d) Kolbe’s reaction

Answer: a) Swartz reaction

Explanation: Swartz: RX + AgF → R–F.

19. Which is major product in Fittig reaction?

a) Alkane

b) Aryl halide

c) Biaryl compound

d) Alcohol

Answer: c) Biaryl compound

Explanation: Ar–X + Ar–X + Na → Ar–Ar.

20. Which of the following is environmental problem of CFCs?

a) Ozone depletion

b) Acid rain

c) Global warming

d) Water pollution

Answer: a) Ozone depletion

Explanation: CFCs release Cl radicals → destroy ozone.

21. Lucas test is used to distinguish:

a) Primary, secondary, tertiary alcohols

b) Primary, secondary, tertiary alkyl halides

c) Aryl and alkyl halides

d) Haloalkanes and haloarenes

Answer: a) Primary, secondary, tertiary alcohols

Explanation: Based on reactivity with HCl/ZnCl2.

22. Order of reactivity towards SN2 is:

a) 1° > 2° > 3°

b) 3° > 2° > 1°

c) 2° > 1° > 3°

d) 3° > 1° > 2°

Answer: a) 1° > 2° > 3°

Explanation: Less steric hindrance → faster SN2.

23. Which is used in dry cleaning?

a) CHCl3

b) CCl4

c) CCl2F2

d) CH2Cl2

Answer: b) CCl4

Explanation: Carbon tetrachloride used as solvent in dry cleaning.

24. Which reaction gives Grignard reagent?

a) RX + Mg → RMgX

b) RX + Na → R–R

c) RX + KOH → ROH

d) RX + AgNO3 → R–ONO2

Answer: a) RX + Mg → RMgX

Explanation: Grignard reagent is organomagnesium halide.

25. Which is correct for chlorobenzene?

a) Highly reactive in SN1

b) Reacts with strong nucleophile at high temp

c) Easily undergoes Friedel-Crafts

d) Readily undergoes Wurtz reaction

Answer: b) Reacts with strong nucleophile at high temp

Explanation: Needs harsh conditions due to resonance stabilization.

26. Which halogen acts as best leaving group in haloalkanes?

a) F–

b) Cl–

c) Br–

d) I–

Answer: d) I–

Explanation: Weakest bond and most stable ion → best leaving group.

27. Which reaction gives benzyl alcohol from benzyl chloride?

a) Hydrolysis with aq. NaOH

b) Reaction with alc. KOH

c) Reaction with Zn/acid

d) Wurtz reaction

Answer: a) Hydrolysis with aq. NaOH

Explanation: OH– replaces Cl– giving alcohol.

28. Which halide is used as insecticide (DDT precursor)?

a) Chlorobenzene

b) Benzyl chloride

c) p-Dichlorobenzene

d) Chloroform

Answer: b) Benzyl chloride

Explanation: Benzyl chloride is used in preparation of DDT.

29. Which reaction converts alkyl halides into alkanes?

a) Wurtz reaction

b) Kolbe reaction

c) Cannizzaro reaction

d) Aldol condensation

Answer: a) Wurtz reaction

Explanation: RX + 2Na + RX → R–R + 2NaX.

30. Which of the following haloalkanes undergo elimination most easily?

a) 1° alkyl halide

b) 2° alkyl halide

c) 3° alkyl halide

d) Allyl halide

Answer: c) 3° alkyl halide

Explanation: More stable carbocation intermediate promotes elimination.