Nomenclature

NCERT Reference:Chapter 6 – Haloalkanes and Haloarenes – Page 154–155

Quick Notes

Haloalkanes and haloarenes are named using either common names or IUPAC names.
Common names treat the compound as a substituted alkane, often named as alkyl halide.
IUPAC names treat the halogen as a prefix substituent (e.g., fluoro-, chloro-, bromo-, iodo-) attached to the parent hydrocarbon.
Numbering in IUPAC names ensures that the halogen gets the lowest possible locant.
Multiple halogens are listed alphabetically, with appropriate prefixes (di-, tri-, tetra-).

Common names are often derived by naming the alkyl group followed by the halide name.

Examples:

Note: These are widely used, especially in laboratory and industrial contexts, but are not systematic, which is why IUPAC names should be used.

Rules for IUPAC Naming of Haloalkanes:

Longest continuous carbon chain is identified as the parent hydrocarbon.
The halogen atom is treated as a substituent and named using the prefix:
- fluoro-
- chloro-
- bromo-
- iodo-
The chain is numbered from the end that gives the halogen the lowest number.
If multiple halogen atoms are present:
- Use prefixes: di-, tri-, tetra-, etc.
- Halogens are listed alphabetically, not by numerical prefix.
Other substituents (like alkyl groups) are also named and arranged alphabetically.

For Example:

For aromatic compounds with halogens:

The halogen is considered a prefix to benzene.
If other substituents are present, their positions are indicated by numbers.
The ring is numbered so that substituents get the lowest numbers possible in the name.

Examples:

Common names are useful but informal while IUPAC names follow strict rules.
The halogen is treated as a substituent and positioned to get the lowest number.
Multiple substituents are listed alphabetically and multiplicative prefixes indicate repetition.
For haloarenes the benzene ring is numbered to give the lowest set of locants for all substituents.