The reaction that does not give benzoic acid as the major product is:

Correct answer: (C) (C) C6H5-CH2OH ->[PCC]. Answer: (C) C6H5-CH2OH ->[PCC] (gives benzaldehyde, not benzoic acid). Solution: Strong oxidants oxidise benzyl alcohol fully to benzoic acid: K2Cr2O7 (A) and KMnO4/H+ (D) both give C6H5COOH. Acetophenone (B), a methyl ketone, undergoes the haloform reaction with NaOCl then H3O+ to give C6H5COOH plus CHCl3. PCC (C) is a mild oxidant that stops the primary alcohol at the aldehyde stage, giving benzaldehyde (C6H5CHO), not benzoic acid.

NEET 2019 Odisha · ChemistryCarbonyl reductionPrevious Year Question

The reaction that does \textbf{not} give benzoic acid as the major product is:

Answer: (C) (C) $C X_{6} H X_{5} - CH X_{2} OH PCC$ . \textbf{Answer:} (C) $C X_{6} H X_{5} - CH X_{2} OH PCC$ (gives benzaldehyde, not benzoic acid).

A.(A) $C X_{6} H X_{5} - CH X_{2} OH K X_{2} Cr X_{2} O X_{7}$
B.(B) $C X_{6} H X_{5} - COCH X_{3} (1) NaOCl (2) H X_{3} O X^{+}$
C.(C) $C X_{6} H X_{5} - CH X_{2} OH PCC$ ✓
D.(D) $C X_{6} H X_{5} - CH X_{2} OH KMnO X_{4} H X^{+}$

Correct Answer

Solution & Explanation

\textbf{Answer:} (C) $C X_{6} H X_{5} - CH X_{2} OH PCC$ (gives benzaldehyde, not benzoic acid). \textbf{Solution:} Strong oxidants oxidise benzyl alcohol fully to benzoic acid: $K X_{2} Cr X_{2} O X_{7}$ (A) and $KMnO X_{4}$ / $H X^{+}$ (D) both give $C X_{6} H X_{5} COOH$ . Acetophenone (B), a methyl ketone, undergoes the haloform reaction with $NaOCl$ then $H X_{3} O X^{+}$ to give $C X_{6} H X_{5} COOH$ plus $CHCl X_{3}$ . PCC (C) is a mild oxidant that stops the primary alcohol at the aldehyde stage, giving benzaldehyde ( $C X_{6} H X_{5} CHO$ ), not benzoic acid.

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