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NEET Chemistry · Organic Compounds Containing Oxygen

Oxidation, reduction and named reactions

Taught in NCERT Class 12 Chemistry, Chapter 8: Aldehydes, Ketones and Carboxylic Acids.

2 verified questions: Easy 0 · Medium 1 · NEET level 1

Sample questions

Sample 1Medium

A reaction scheme shows two molecules of benzaldehyde, C6H5CHO, heated with concentrated aqueous sodium hydroxide, the arrow leading to two products X and Y. What are X and Y?

  1. A

    Benzoic acid and benzene

  2. B

    An aldol, 3-hydroxy-2,3-diphenylpropanal, and water

  3. C

    Toluene and sodium benzoate

  4. D

    Benzyl alcohol and sodium benzoate

Show the answer
The answer is D.

Aldehydes with no α-hydrogen undergo the Cannizzaro reaction with concentrated alkali. One molecule of benzaldehyde is reduced to benzyl alcohol and the other is oxidised to sodium benzoate.

  • A.

    Benzaldehyde is not decarboxylated here; one molecule is oxidised to the benzoate salt and the other reduced to the alcohol.

  • B.

    Benzaldehyde has no α-hydrogen, so it cannot undergo aldol condensation.

  • C.

    The reduced product is the alcohol, C6H5CH2OH, not the hydrocarbon toluene.

NCERT: Class 12 Chemistry, Chapter 8

Sample 2NEET level

Match the reactions in List I with the reagents used in List II. List I: A. Rosenmund reduction B. Stephen reaction C. Clemmensen reduction D. Etard reaction List II: I. CrO2Cl2 in CS2, then H3O⁺ II. Zn-Hg and concentrated HCl III. H2, Pd-BaSO4 IV. SnCl2 and HCl, then H3O⁺

  1. A

    A-IV, B-III, C-II, D-I

  2. B

    A-III, B-IV, C-II, D-I

  3. C

    A-III, B-IV, C-I, D-II

  4. D

    A-II, B-IV, C-III, D-I

Show the answer
The answer is B.

Rosenmund reduction converts acyl chlorides to aldehydes with H2 over Pd on BaSO4, and the Stephen reaction reduces nitriles to aldehydes with SnCl2/HCl followed by hydrolysis. Clemmensen reduction converts C=O to CH2 with zinc amalgam and concentrated HCl, and the Etard reaction oxidises toluene to benzaldehyde with chromyl chloride.

  • A.

    Swaps the reagents of the Rosenmund and Stephen reactions.

  • C.

    Swaps Clemmensen (Zn-Hg/HCl) and Etard (CrO2Cl2) reagents.

  • D.

    Rosenmund uses H2/Pd-BaSO4, not Zn-Hg/HCl, which is Clemmensen's reagent.

NCERT: Class 12 Chemistry, Unit 8 (Aldehydes, Ketones and Carboxylic Acids), Preparation of Aldehydes and Ketones and Chemical Reactions: Reduction

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