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Aldehydes, Ketones and Carboxylic Acids · Question 38

AIPMT 2015MCQEasy📈 Topic in 38% papers+4−1
1

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.

Answer

(1) hydrazine in presence of feebly acidic solution

Solution

As per NCERT, ammonia derivatives Z-NH2 (hydroxylamine, hydrazine, phenylhydrazine, semicarbazide …) add to the carbonyl group in a weakly acidic medium and the adduct then loses water (addition–elimination):

>C=O + H2N-NH2 >C(OH)-NH-NH2 -H2O >C=N-NH2 (hydrazone)

HCN, NaHSO3 and Grignard reagents give only addition products (cyanohydrin, bisulphite adduct, alcohol after hydrolysis) — no elimination of water.

Answer: (1)

AIPMT 2015

Keep practising — Aldehydes, Ketones and Carboxylic Acids

2

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

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

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
AIPMT 2015 (Cancelled)
4

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
AIPMT 2015 (Cancelled)
5

Which one is most reactive towards nucleophilic addition reaction?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2014
6

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
NEET 2013
7

In the following reaction: HC CH [Hg2+]H2SO4 'P' Product 'P' will not give

  1. Tollen's reagent test
  2. Brady's reagent test
  3. Victor Meyer test
  4. Iodoform test
NEET 2013 (Karnataka)
8

Consider the reaction : RCHO + NH2NH2 RCH = N - NH2 What sort of reaction is it?

  1. Electrophilic addition-elimination reaction
  2. Free radical addition-elimination reaction
  3. Electrophilic substitution-elimination reaction
  4. Nucleophilic addition-elimination reaction
AIPMT 2012 (Mains)
9

Which of the following compounds will give a yellow precipitate with iodine and alkali?

  1. Acetophenone
  2. Methyl acetate
  3. Acetamide
  4. 2-Hydroxypropane
AIPMT 2012 (Mains)
10

Consider the following reaction [figure] The product A is

  1. C6H5CHO
  2. C6H5OH
  3. C6H5COCH3
  4. C6H5Cl
AIPMT 2012 (Mains)
11

In the following sequence of reactions CH3-Br KCNA H3O+B [ether]LiAlH4C the end product (C) is

  1. acetone
  2. methane
  3. acetaldehyde
  4. ethyl alcohol
AIPMT 2012 (Prelims)

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