Which of the following compounds is formed by the oxidation of ethanol?

Analyze the question: Ethanol (CH₃CH₂OH) is a primary alcohol. We need the product formed when it is oxidized.

Concept: Primary alcohols are oxidized in stages by oxidizing agents such as acidified potassium dichromate(VI) (K₂Cr₂O₇/H⁺) or acidified potassium permanganate (KMnO₄/H⁺):

Primary alcohol → Aldehyde → Carboxylic acid

Solution:

1. Ethanol is oxidized to ethanal (an aldehyde): CH₃CH₂OH → CH₃CHO

2. With further oxidation, ethanal becomes ethanoic acid (a carboxylic acid): CH₃CHO → CH₃COOH

The carbon chain stays the same length (2 carbons), so the final product is ethanoic acid, CH₃CO₂H.

Checking the options:

• A. C₂H₄CO₂H: has 3 carbons and is not a proper formula for a common acid. Wrong.
• B. C₂H₅CO₂H: propanoic acid (3 carbons). Oxidizing ethanol does not add a carbon. Wrong.
• C. CH₃OH: methanol, an alcohol with only 1 carbon. It is not an oxidation product of ethanol. Wrong.
• D. CH₃CO₂H: ethanoic acid (2 carbons). Correct.

Tip: Oxidation keeps the number of carbon atoms the same. Ethanol (2 C) gives ethanal (2 C) and then ethanoic acid (2 C). Count the carbons in the options and you can eliminate the wrong ones quickly. This is also how vinegar forms when wine or palm wine goes sour: ethanol is oxidized to ethanoic acid.