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Aldehydes, Ketones and Carboxylic Acids appeared 1 time across 1 year — 2.2% of Chemistry. This question is from Identification of Carbonyl Compounds.

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Compound $P (C₈H₈O)$ $P (C_8H_8O)$ gives a red orange precipitate with 2,4-DNP reagent and it does not reduce Fehling's reagent. On drastic oxidation with chromic acid, P gives an aromatic product Q that produces effervescence on treating with aq. $NaHCO₃$ $NaHCO_3$. Compounds P and Q, respectively, are:

Q: Compound P (C8H8O) gives a red orange precipitate with 2,4-DNP reagent and it does not reduce Fehling's reagent. On drastic oxidation with chromic acid, P gives an aromatic product Q that produces eff

1. 2,4-DNP positive Carbonyl group present. 2. Fehling test negative Ketone (Acetophenone). 3. Drastic oxidation of acetophenone (C8H8O) with chromic acid yields Benzoic acid (Q = C6H5COOH). 4. Benzoic acid gives effervescence with NaHCO3 (CO2 gas). P is Acetophenone and Q is Benzoic Acid. Positive 2,4-DNP + Negative Fehling = Aromatic Ketone (Acetophenone). Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

A. (1) Option A
Identification of Carbonyl Compounds
B. (2) Option B
Identification of Carbonyl Compounds
C. (3) Option C
Identification of Carbonyl Compounds
D. (4) Option D
Identification of Carbonyl Compounds

Solution & Explanation

Related Formula

Degree of Unsaturation = C + 1 - (H)/(2) = 8 + 1 - 4 = 5

Core Logic

2,4-DNP positive $\implies$ Carbonyl group present.
Fehling test negative $\implies$ Ketone (Acetophenone).
Drastic oxidation of acetophenone ( $C₈H₈O$ $C_8H_8O$) with chromic acid yields Benzoic acid ( $Q = C₆H₅COOH$ $Q = C_6H_5COOH$).
Benzoic acid gives effervescence with $NaHCO₃$ $NaHCO_3$ ( $CO₂$ $CO_2$ gas).

Step 1: Conclusion

P is Acetophenone and Q is Benzoic Acid.

Pattern Recognition

Positive 2,4-DNP + Negative Fehling = Aromatic Ketone (Acetophenone).

Chapter Mix

Class 12 Chemistry: Aldehydes, Ketones and Carboxylic Acids

Reference Study Guides

Aldehydes Ketones And Carboxylic Acids

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JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%) | JEE Physics: Waves (+15.5%) | Electrostatics: Concentric Shells (-29.7%) | Modern Physics: Photoelectric Clones (+34.2%) | Mathematics: Definite Integrals (+18.1%) | Chemistry: Coordination Splitting (-11.4%)