Naming esters by identifying alkyl and acyl groups

Steps:

• Examine the ester formula: the chain after the carbonyl (C=O) is CH3-CH2-CH2-, a 4-carbon chain from butanoic acid, so "butanoate."
• Identify the group attached to the oxygen: CH3-CH2-CH2-, a 3-carbon propyl group.
• Name as alkyl from alcohol + alkanoate from acid: propyl butanoate.
• Confirm no branches or other features alter the naming.

Why B is correct:

• Propyl butanoate matches the IUPAC rule for esters, where the alkyl (propyl, C3H7-) precedes the alkanoate (butanoate, C3H7COO-) from the parent acid.

Why the others are wrong:

• A: Swaps chains; butyl (C4) would be the alcohol part, butanoate the acid—mismatches structure.
• C: Ethanoate implies 2-carbon acid chain (CH3COO-), but acid part has 4 carbons.
• D: Propanoate implies 3-carbon acid chain (C2H5COO-), but acid part has 4 carbons.

Final answer: B