IUPAC Nomenclature
The systematic naming rules for organic compounds.
The 3-Step Naming System
Substituents
chloro-, methyl-
Longest Chain
meth-, eth-, prop-
Main Functional Group
-ol, -oic acid, -al
The Priority Algorithm
Number the chain so the highest priority group gets the lowest locant.
Priority Hierarchy (Highest → Lowest)
Carboxylic Acid > Ester > Amide > Nitrile > Aldehyde > Ketone > Alcohol > Amine > Alkene > Halogen / Alkyl
Examiner Trap: The "Ghost" Carbon
When naming Nitriles (\(-CN\)) or Carboxylic Acids (\(-COOH\)), the carbon in the functional group counts as Carbon-1.
\(CH_3-CH_2-CN\) is Propanenitrile (3 Carbons), NOT Ethanenitrile.