Question

Furan, on treatment with butyllithium followed by reaction with carbon dioxide, produces which compound on acidification?

• A. Furfural
• B. Furoic acid
• C. Furan-3-carboxylic acid
• D. Furan-3-aldehyde

Hint:

Butyllithium metalates furan at its most acidic position, C-2, next to the ring oxygen; reaction with CO2 then installs a carboxylic acid there.

Answer 1

The Correct Option is B

Step 1: Furan is an electron-rich five-membered aromatic heterocycle. Its 2- and 5-position hydrogens are most acidic because the resulting carbanion is stabilized by the neighboring oxygen.

Step 2: Butyllithium removes the proton at the 2-position to give 2-lithiofuran plus butane.

Step 3: \[Furan + n\text{-}BuLi \rightarrow 2\text{-lithiofuran} + C_4H_{10}\]

Step 4: The organolithium at the 2-position attacks CO2 to form a lithium carboxylate at that position.

Step 5: \[2\text{-lithiofuran} + CO_2 \rightarrow \text{furan-2-carboxylate lithium salt}\]

Step 6: Acidic workup gives furan-2-carboxylic acid, commonly known as furoic acid.

\[\boxed{\text{Furoic acid (furan-2-carboxylic acid)}}\]