Select Board & Class

Login

Haloalkanes and Haloarenes

Classification and Nomenclature

Classification

  • Based on number of halogen atoms

  • Monohalogen

  • Dihalogen

  • Polyhalogen (tri-, tetra-, penta- etc.)

  • Examples of haloalkanes:

  • Examples of haloarenes:

  • Based on the hybridisation of C−atom of C−X bond of monohalocompounds

  • Compounds containing sp3 C−X bond (X = F, Cl, Br, I)

(i) Alkyl halides or haloalkanes (R−X) They form homologous series of general formula CnH2n+1X. They are further classified into primary, secondary, and tertiary.

(ii) Allylic halides Compounds containing halogen atom bonded to an allylic carbon

(iii) Benzylic halides Compounds containing halogen atom bonded to an sp3 hybridised carbon atom next to an aromatic ring

To test your knowledge of this concept, solve the following puzzle.

  • Compounds containing sp2 C−X bond (X = F, Cl, Br, I)

(i) Vinylic halides Compounds containing halogen atom bonded to a vinylic carbon

(ii) Aryl halides Compounds containing halogen atom bonded to an sp2 hybridised carbon atom of an aromatic ring

Nomenclature

  • For haloalkanes

  • Common name Name of alkyl group followed by name of the halide

  • IUPAC name Named as halo-substituted hydrocarbon in IUPAC

  • Examples:

Structure

Common Name

IUPAC Name

CH3CH2CH2CH2Br

n−Butyl bromide

1-Bromobutane

Isobutyl chloride

1-Chloro-2-methyl-propane

sec-butyl bromide

2-Bromobutane

CH3CH2CH(Cl)CH3

sec-Butyl chloride

2-Chlorobutane

(CH3)3CCH2Br

neo-Pentyl bromide

1-Bromo-2,2-dimethylpropane

(CH3)3CBr

tert-Butyl bromide

2-Bromo-2-methylpropane

CH2Cl2

Methylene chloride

Dichloromethane

  • For haloarenes

  • Named as halo-substituted hydrocarbon (for both common and IUPAC name)

  • For dihalogen derivatives:

In common names prefixes o-, m-, p- are used

In IUPAC names numerals 1, 2; 1, 3; 1, 4 are used

  • Examples:

Structure

Common name

IUPAC name

Chlorobenzene

Chlorobenzene

o-Dibromobenzene

1,2-Dibromobenzene

sym-Trichlorobenzene

1,3,5-Trichlorobenzene

o-Chlorotoluene

1-Chloro-2-methylbenzene

or

2-Chlorotoluene

Benzyl chloride

Chlorophenylmethane

Nature of C−X bond

  • C-atom bears partial positive charge and X-atom bears partial negative charge.

  • C−X bond length increases down the group.

  • Reason − Size of halogen atom increases down the group.

Classification

  • Based on number of halogen atoms

  • Monohalogen

  • Dihalogen

  • Polyhalogen (…

To view the complete topic, please

What are you looking for?

Syllabus