COMPASSLearning
RegisterLogin

JEE Main · 2021 · 27 Jul 2021 · Shift 1 · Aldehydes Ketones and Carboxylic Acids

WhatsApp Email
Which one of the following compounds will give orange precipitate when treated with 2,4-Dinitrophenyl hydrazine?
  1. (A)(see structure)
  2. (B)(see structure)
  3. (C)(see structure)
  4. (D)(see structure)
    ✓ Correct

Answer: (D)

Solution

-Dinitrophenylhydrazine condenses with a free aldehyde or ketone carbonyl group to give a -dinitrophenylhydrazone, which separates as an orange to red solid. The reaction needs a carbonyl carbon electrophilic enough to be attacked by this weakly nucleophilic hydrazine.
In ethyl salicylate and ethyl benzoate the carbonyl carbon carries an ester oxygen, and in salicylic acid it carries a hydroxyl oxygen; in each case the lone pair of that oxygen is donated into the carbonyl and lowers its electrophilic character, so no hydrazone is formed. Acetophenone has a ketonic carbonyl with no such donor attached to it and condenses readily.
The orange precipitate is given by acetophenone.

JEE Main · 2021 · 27 Jul 2021 · Shift 1 · Single correct option

Practise more: all JEE Main PYQs on Aldehydes Ketones and Carboxylic Acids →

More JEE Main questions on Aldehydes Ketones and Carboxylic Acids

  1. An organic compound "P" of molecular formula gives positive iodoform test but negative Tollen's test. When "P" is treated with dilute acid, it produces "Q". "Q" gives positive Tollen's test and also iodoform test. The structure of …
    JEE Main 2026View solution →
  2. Match List-I with List-II.

    List-I (Reaction Name - Involving aldehydes):
    I. Etard Reaction
    II. Rosenmund Reduction
    III. Gatterman-Koch Reaction
    IV. Stephen Reaction

    List-II (Reagents):
    A. , Pd-
    B. , HCl
    C. …
    JEE Main 2026View solution →
  3. The compound A, reacts with acetophenone to form a single product via cross-Aldol condensation. The compound A on reaction with conc. NaOH forms a substituted benzyl alcohol as
    JEE Main 2026View solution →
  4. ' ' is the product which is obtained from propanenitrile and stannous chloride in the presence of hydrochloric acid followed by hydrolysis. ' y ' is the product which is obtained from the but-2-ene by the ozonolysis followed by hydrolysis. From the following, which product is …
    JEE Main 2026View solution →
  5. From the given following (A to D) cyclic structures, those which will not react with Tollen's reagent are :
    JEE Main 2026View solution →
  6. Iodoform test can differentiate between
    A. Methanol and Ethanol
    B. and
    C. Cyclohexene and cyclohexanone
    D. Diethyl ether and Pentan-3-one
    E. Anisole and acetone

    Choose the correct answer from the …
    JEE Main 2026View solution →