Using IUPAC guidelines, what is the correct name for the carboxylic acid with the structure ${\mathrm{CH}}_3\mathrm{CH}-\mathrm{COOH}$?

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

Answer: (B)

Verified step by step guidance

1. Identify the longest carbon chain that includes the carboxylic acid functional group (-COOH). The carboxylic acid carbon is always counted as carbon 1.
2. Count the total number of carbons in the chain starting from the carboxyl carbon. In this case, the structure is CH3-CH-COOH, which corresponds to three carbons in total.
3. Use the IUPAC naming convention for carboxylic acids, where the suffix '-oic acid' is added to the alkane name corresponding to the number of carbons in the chain. For three carbons, the base alkane is propane, so the acid name is 'propanoic acid'.
4. Verify that no other functional groups or substituents change the base name or require additional prefixes or locants.
5. Conclude that the correct IUPAC name for the compound CH3-CH-COOH is 'propanoic acid'.