What is the IUPAC name of the molecule with formula C2H5COOH?

What is the IUPAC name of the molecule with formula C2H5COOH?

• A. Propanoic acid
• B. Ethanoic acid
• C. Butanoic acid
• D. Methanoic acid

Answer: (A)

Think about how IUPAC names carboxylic acids: use the longest carbon chain that includes the carboxyl group and add the suffix -anoic acid, counting the carboxyl carbon as carbon 1. The molecule C2H5COOH can be drawn as CH3-CH2-COOH, a three-carbon chain with the carboxyl group at one end. That three-carbon chain gives the root name prop-, so the IUPAC name is propanoic acid. The other options correspond to shorter or longer chains (one carbon for methanoic, two for ethanoic, four for butanoic), which is why they don’t fit this structure.

Think about how IUPAC names carboxylic acids: use the longest carbon chain that includes the carboxyl group and add the suffix -anoic acid, counting the carboxyl carbon as carbon 1. The molecule C2H5COOH can be drawn as CH3-CH2-COOH, a three-carbon chain with the carboxyl group at one end. That three-carbon chain gives the root name prop-, so the IUPAC name is propanoic acid. The other options correspond to shorter or longer chains (one carbon for methanoic, two for ethanoic, four for butanoic), which is why they don’t fit this structure.