Question

Write the IUPAC nomenclature of the following organic compounds:
(A) $CH_3 - CH_2 - \overset{\text{O}}{\overset{||}{\text{C}}} - CH_2 - \underset{\text{CH}_3}{\underset{|}{\text{CH}}} - CH_3$
(B) $Ph - CH = CH - CHO$

Hint:

Priority Order for Numbering: Functional Group > Double Bond > Triple Bond > Substituents. Always start numbering to give the principal functional group the lowest possible locant.

Answer 1

(A) Structure Analysis: \[ \text{Structure:} \quad CH_3 - CH_2 - C(=O) - CH_2 - CH(CH_3)_2 \]

• Longest Chain: 6 Carbons containing the ketone group.
• Numbering: Start from the left to give the Ketone (functional group) the lowest number.
  • C1: $CH_3$
  • C2: $CH_2$
  • C3: $C=O$ (Ketone)
  • C4: $CH_2$
  • C5: $CH$ (with a methyl substituent)
  • C6: $CH_3$
• Substituent: Methyl group at position 5.
• IUPAC Name: 5-Methylhexan-3-one

(B) Structure Analysis: \[ \text{Structure:} \quad C_6H_5 - CH = CH - CHO \]

• Principal Group: Aldehyde ($-CHO$). Carbon of CHO is always C1.
• Chain: Propene chain.
• C1: $CHO$
• C2: $CH=$
• C3: $=CH-$ (attached to Phenyl ring)
• Substituent: Phenyl group ($Ph-$) at C3.
• Unsaturation: Double bond starts at C2.
• IUPAC Name: 3-Phenylprop-2-enal (Also commonly known as Cinnamaldehyde).