Nomenclature

Full Notes

Amines are named using two major systems: the common naming system and the IUPAC system. These systems take into account the number and types of alkyl or aryl groups attached to the nitrogen atom.

Common System of Nomenclature

Primary aliphatic amines are named by prefixing alkyl groups to the word “amine”.

• CH₃NH₂ = Methylamine
• CH₃CH₂NH₂ = Ethylamine

Secondary and tertiary amines:

• If identical alkyl groups are present: Use di and tri prefix
  (CH₃)₂NH = Dimethylamine
• If different alkyl groups are attached (mixed amine), name them in alphabetical order:
  CH₃NHCH₂CH₃ = Ethylmethylamine

IUPAC System of Nomenclature

Primary Amines

Named by replacing the final “e” of the parent alkane with “amine”.

• CH₃NH₂ = Methanamine
• CH₃CH₂CH₂NH₂ = Propan-1-amine
• CH₃CH(NH₂)CH₃ = Propan-2-amine

For molecules with two or more –NH₂ groups: Use “diamine”, “triamine” etc., with position numbers.

• H₂N–CH₂–CH₂–NH₂ = Ethane-1,2-diamine

Secondary and Tertiary Amines

The longest carbon chain is chosen as the parent. Alkyl groups on the nitrogen atom are treated as substituents and denoted by “N-”.

• CH₃NHCH₂CH₃ = N-Methylethanamine
• (CH₃)₂NCH₂CH₃ = N,N-Dimethylethanamine

Aromatic Amines

When –NH₂ is attached directly to an aromatic ring:

• C₆H₅NH₂ = Benzenamine (IUPAC), Aniline (common)
• Substituted derivatives:
  • 2-Methylbenzenamine (IUPAC) = o-Toluidine (common)
  • 4-Bromobenzenamine (IUPAC) = p-Bromoaniline (common)

Summary

• Common names use alkyl names followed by amine.
• IUPAC names replace the alkane suffix with amine and use positions for chains.
• Use N prefixes for groups on nitrogen in secondary and tertiary amines.
• Aromatic amines are named as benzenamine or aniline and positional isomers are indicated with numbers or o, m, p in common names.