Which organic acid can be formed from ethanol?

• A. C3H7OH
• B. Formic acid
• C. Acetic acid
• D. Butanoic acid

Answer: (C)

Oxidizing a primary alcohol typically takes you first to an aldehyde and then to a carboxylic acid, without changing the carbon count. Ethanol (two carbons) is oxidized to acetaldehyde (two carbons) and further to acetic acid (two carbons). So the product most consistent with simply oxidizing ethanol is acetic acid.

The other options don’t fit this oxidation pattern. A two-carbon alcohol is not an acid, so it isn’t the expected product. Formic acid would require forming a one-carbon fragment, which isn’t how ethanol oxidizes. Butanoic acid has four carbons, which isn’t produced from a two-carbon starting material by straightforward oxidation.