How are ketones named using IUPAC rules?

Here’s a simple guide for naming ketones with IUPAC rules:

Rules for Ketones

1. Find the longest carbon chain that contains the carbonyl group (C=O).
2. Replace “-e” of the parent alkane with “-one”.
   • Example: propane → propanone.
3. Number the chain so that the carbonyl carbon gets the lowest possible number.
4. Indicate the position of the carbonyl group by a number (only needed if the chain has 5 or more carbons, or if there’s ambiguity).
5. Name and number any substituents (branches) as usual.
6. For cyclic ketones, add “-one” at the end of the ring name (e.g., cyclohexanone).

Examples

• CH₃–CO–CH₃ → Propanone (common name: acetone)
• CH₃–CO–C₂H₅ → Butan-2-one
• CH₃–CH₂–CO–CH₃ → Butan-2-one (same as above, just longer form)
• C₆H₁₀O (a ring with C=O) → Cyclohexanone

In short:
Alkane name – e + one = Ketone name.