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Aldehydes, Ketones and Carboxylic Acids

NEET 2017MCQMedium📈 Topic in 25% papers+4−1
Ques. 1NEET 2017

Consider the reactions, [figure] Identify A, X, Y and Z.

  1. A-Methoxymethane, X-Ethanol, Y-Ethanoic acid, Z-Semicarbazide.
  2. A-Ethanal, X-Ethanol, Y-But-2-enal, Z-Semicarbazone.
  3. A-Ethanol, X-Acetaldehyde, Y-Butanone, Z-Hydrazone.
  4. A-Methoxymethane, X-Ethanoic acid, Y-Acetate ion, Z-Hydrazine.

Answer

(2) A-Ethanal, X-Ethanol, Y-But-2-enal, Z-Semicarbazone.

Solution

∵ X (C2H6O) is dehydrogenated by Cu at 573 K ⇒ X is an alcohol: X = ethanol.

CH3CH2OH [573 K]Cu CH3CHO + H2 ⇒ A = ethanal.

∵ A gives a silver mirror with Tollens' reagent ⇒ A is an aldehyde (confirms ethanal).

Aldol condensation of ethanal on heating with alkali:

2CH3CHO dil. NaOH CH3CH(OH)CH2CHO

CH3CH=CHCHO + H2O ⇒ Y = but-2-enal.

With semicarbazide:

CH3CHO + NH2NHCONH2 CH3CH=NNHCONH2 + H2O ⇒ Z = semicarbazone.

∴ A-Ethanal, X-Ethanol, Y-But-2-enal, Z-Semicarbazone.

Answer: (2)

Keep practising — Aldehydes, Ketones and Carboxylic Acids

Ques. 2NEET 2016 (Phase 1)

Which of the following reagents would distinguish cis-cyclopentane-1,2-diol from the trans-isomer?

  1. MnO2
  2. Aluminium isopropoxide
  3. Acetone
  4. Ozone
Ques. 3NEET 2016 (Phase 1)

The product formed by the reaction of an aldehyde with a primary amine is

  1. carboxylic acid
  2. aromatic acid
  3. Schiff's base
  4. ketone
Ques. 4NEET 2016 (Phase 2)

The correct order of the strengths of the carboxylic acids [figure] is

  1. I > II > III
  2. II > III > I
  3. III > II > I
  4. II > I > III
Ques. 5NEET 2016 (Phase 2)

The correct structure of the product 'A' formed in the reaction [figure]

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 6AIPMT 2015

Reaction of a carbonyl compound with one of the following reagents involves nucleophilic addition followed by elimination of water. The reagent is

  1. hydrazine in presence of feebly acidic solution
  2. hydrocyanic acid
  3. sodium hydrogen sulphate
  4. a Grignard reagent.
Ques. 7AIPMT 2015

Which one of the following esters gets hydrolysed most easily under alkaline conditions?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 8AIPMT 2015 (Cancelled)

Treatment of cyclopentanone [figure] with methyl lithium gives which of the following species ?

  1. Cyclopentanonyl radical
  2. Cyclopentanonyl biradical
  3. Cyclopentanonyl anion
  4. Cyclopentanonyl cation
Ques. 9AIPMT 2015 (Cancelled)

An organic compound 'X' having molecular formula C5H10O yields phenylhydrazone and gives negative response to the iodoform test and Tollens' test. It produces n-pentane on reduction. 'X' could be

  1. 3-pentanone
  2. n-amyl alcohol
  3. pentanal
  4. 2-pentanone
Ques. 10AIPMT 2014

Which one is most reactive towards nucleophilic addition reaction?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 11NEET 2013

Reaction by which benzaldehyde cannot be prepared

  1. [figure] + CO + HCl in presence of anhydrous AlCl3
  2. [figure] + Zn/Hg and conc. HCl
  3. [figure] + CrO2Cl2 in CS2 followed by H3O+
  4. [figure] + H2 in presence of Pd-BaSO4

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