Question

What is the IUPAC name of the compound \( \text{CH}_3\text{CH}_2\text{COCH}_2\text{CH}_3 \)?

• A. Pentan-3-one
• B. Butan-2-one
• C. Pentan-2-one
• D. Hexan-3-one

Hint:

\textbf{Key Fact:} In IUPAC nomenclature for ketones, the carbonyl group gets the lowest possible number in the longest carbon chain.

Answer 1

The Correct Option is A

• Identify the Structure: The compound CH₃CH₂COCH₂CH₃ has the structure CH₃-CH₂-C(=O)-CH₂-CH₃.
• Count Carbon Atoms: The longest chain containing the carbonyl group has 5 carbons: C-C-C(=O)-C-C, so the base name is pentane.
• Identify Functional Group: The carbonyl group (C=O) indicates a ketone, so the suffix is "-one."
• Number the Chain: Number the chain to give the carbonyl group the lowest possible number: CH₃(5)-CH₂(4)-C(=O)(3)-CH₂(2)-CH₃(1). The carbonyl is at position 3.
• Name the Compound: The IUPAC name is pentan-3-one.
• Conclusion: The correct answer is (1) Pentan-3-one.