Question

Which compound of the following does \(\underline{not}\) reduce Fehling's solution?

• A. CH$_3$COOH
• B. HCOOH
• C. HCHO
• D. CH$_3$CHO

Hint:

All aliphatic aldehydes reduce Fehling's reagent. Among carboxylic acids, only formic acid (HCOOH) reduces it; common acids like acetic acid do not.

Answer 1

The Correct Option is A

Fehling's solution is reduced by aldehydes and by formic acid (HCOOH), forming red Cu$_2$O.
- HCHO (formaldehyde) and CH$_3$CHO (acetaldehyde) are aliphatic aldehydes $\Rightarrow$ give positive Fehling test.
- HCOOH is a special case: though it is a carboxylic acid, it is readily oxidized to CO$_2$ and reduces Fehling's solution.
- CH$_3$COOH (acetic acid) is a typical carboxylic acid and is not a reducing agent $\Rightarrow$ does not reduce Fehling's solution.
\[ \boxed{\text{CH}_3\text{COOH does not reduce Fehling's solution.}} \]