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Haloalkanes and Haloarenes

NCERT Class 12 Chemistry Chapter 6

Haloalkanes and Haloarenes for Class 12 Chemistry, JEE and NEET: preparation, the C–X bond, SN1 and SN2 mechanisms, elimination and polyhalogen compounds.

8 topics Updated 8 Nov 2026

For: Class 12, JEE and NEET

In the syllabus: JEE Class 12 syllabus, NEET Class 12 syllabus

With your textbook

NCERT Chemistry Part II (Class 12), Chapter 6 “Haloalkanes and Haloarenes”, reprint 2026-27.

Open the official NCERT chapter (PDF, 4.3 MB, ncert.nic.in)

Checked on 19 Oct 2026.

Learn in this order

  1. Classification of haloalkanes and haloarenes

    Mono-, di-, polyhalogen; 1°, 2°, 3°, allylic, benzylic, vinylic and aryl halides.

    NCERT Section 6.1 8 min read 2 solved examples 4 practice questions

  2. Nomenclature of haloalkanes and haloarenes

    Common and IUPAC names, o-, m-, p- or 1,2-, 1,3-, 1,4-, gem and vic dihalides.

    NCERT Section 6.2 8 min read 3 solved examples 4 practice questions

  3. Nature of the C–X bond in haloalkanes

    Why it is polar, and NCERT Table 6.2’s bond lengths, bond enthalpies and dipole moments.

    NCERT Section 6.3 8 min read 2 solved examples 4 practice questions

  4. Preparation of haloalkanes

    From alcohols (HX, PX, PCl, SOCl), alkanes and alkenes, and the Finkelstein and Swarts reactions.

    NCERT Section 6.4 14 min read 4 solved examples 8 practice questions

  5. Preparation of haloarenes

    Electrophilic substitution with Fe or FeCl, why iodine and fluorine differ, Sandmeyer’s reaction.

    NCERT Section 6.5 11 min read 4 solved examples 8 practice questions

  6. Physical properties of haloalkanes and haloarenes

    Boiling point order, branching, para isomers, density and solubility.

    NCERT Section 6.6 10 min read 4 solved examples 8 practice questions

  7. Chemical reactions of haloalkanes and haloarenes

    SN1 vs SN2, chirality, Saytzeff, Grignard, Wurtz–Fittig, haloarene reactivity.

    NCERT Section 6.7 24 min read 6 solved examples 11 practice questions

  8. Polyhalogen compounds: uses and effects

    Uses and effects of CHCl, chloroform, iodoform, CCl, freons and DDT, and why chloroform is kept dark.

    NCERT Section 6.8 13 min read 4 solved examples 8 practice questions

Key formulas in this chapter

Classification

  • Alkyl halides: CHX
  • 1°, 2°, 3°: the halogen carbon carries one, two or three other carbons

Nomenclature

  • CHCHCl: ethylidene chloride = 1,1-dichloroethane
  • ClCHCHCl: ethylene dichloride = 1,2-dichloroethane

Nature of C–X bond

  • Bond length: C–F < C–Cl < C–Br < C–I
  • Bond enthalpy: C–F > C–Cl > C–Br > C–I
  • Dipole moment: CHCl > CHF > CHBr > CHI

Preparation of haloalkanes

  • R–OH + HCl (ZnCl) → R–Cl + HO
  • R–OH + SOCl → R–Cl + SO + HCl
  • 3R–OH + PX → 3R–X + HPO
  • R–OH + PCl → R–Cl + POCl + HCl
  • R–X + NaI → R–I + NaX (dry acetone)
  • HC–Br + AgF → HC–F + AgBr
  • Reactivity of alcohols with HX: 3° > 2° > 1°

Preparation of haloarenes

  • CH + Cl (Fe or FeCl) → CHCl + HCl
  • CHNH + NaNO + 2HCl (273–278 K) → CHNCl + NaCl + 2HO
  • CHNCl (CuCl) → CHCl + N
  • CHNCl + KI → CHI + KCl + N

Physical properties

  • Boiling point: RI > RBr > RCl > RF (same R)
  • CHBr b.p.: 375 K (1-bromo) > 364 K (2-bromo) > 346 K (2-bromo-2-methyl)
  • Dichlorobenzene m.p.: para 323 K > ortho 256 K > meta 249 K
  • Density: n-CHCl 0.89 < n-CHBr 1.335 < n-CHI 1.747 g/mL
  • Density: CHCl 1.336 < CHCl 1.489 < CCl 1.595 g/mL

Chemical reactions

  • R–X + Nu → R–Nu + X
  • SN2 rate = k[RX][Nu]
  • SN1 rate = k[RX]
  • SN2: CHX > 1° > 2° > 3°; SN1: 3° > 2° > 1° > CHX
  • R–I > R–Br > R–Cl ≫ R–F
  • RMgX + HO → RH + Mg(OH)X
  • 2RX + 2Na → R–R + 2NaX (dry ether)
  • CHX + 2Na + RX → CHR + 2NaX (dry ether)
  • 2CHX + 2Na → CH–CH + 2NaX (dry ether)

Polyhalogen compounds

  • 2CHCl + O → 2COCl + 2HCl (light)
  • Freon 12: CClF
  • DDT: (ClCH)CH–CCl, CHCl

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