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Aldehydes, Ketones and Carboxylic Acids · Question 53

AIPMT 2011 (Mains)MCQEasy📈 Topic in 38% papers+4−1
1

The order of reactivity of phenyl magnesium bromide (PhMgBr) with the following compounds: [figure]

  1. III > II > I
  2. II > I > III
  3. I > III > II
  4. I > II > III

Answer

(4) I > II > III

Solution

The reaction of PhMgBr with a carbonyl compound is a nucleophilic addition at the carbonyl carbon.

As per NCERT, aldehydes are more reactive than ketones in nucleophilic addition because (a) two bulky groups in ketones hinder the approach of the nucleophile and (b) two electron-releasing groups reduce the electrophilicity of the carbonyl carbon.

⇒ I (ethanal, an aldehyde) is the most reactive.

⇒ II (propanone) has two CH3 groups: less reactive.

⇒ III (benzophenone) has two bulky phenyl groups whose resonance with C=O also lowers the positive charge on the carbonyl carbon: least reactive.

∴ I > II > III

Answer: (4)

AIPMT 2011 (Mains)

Keep practising — Aldehydes, Ketones and Carboxylic Acids

2

Clemmensen reduction of a ketone is carried out in the presence of which of the following?

  1. Glycol with KOH
  2. Zn-Hg with HCl
  3. LiAlH4
  4. H2 and Pt as catalyst
AIPMT 2011 (Prelims)
3

Following compounds are given (i) CH3CH2OH (ii) CH3COCH3 (iii) CH3- CH3 |CHOH (iv) CH3OH Which of the above compound(s), on being warmed with iodine solution and NaOH, will give iodoform?

  1. (i), (iii) and (iv)
  2. Only (ii)
  3. (i), (ii) and (iii)
  4. (i) and (ii)
AIPMT 2010 (Mains)
4

Which one of the following compounds will be most readily dehydrated?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2010 (Mains)
5

In a set of reactions, ethylbenzene yielded a product D. [figure] D would be

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2010 (Prelims)
6

Which of the following reactions will not result in the formation of carbon-carbon bonds?

  1. Reimer-Tiemann reaction
  2. Cannizzaro reaction
  3. Wurtz reaction
  4. Friedel-Crafts acylation
AIPMT 2010 (Prelims)
7

Among the given compounds, the most susceptible to nucleophilic attack at the carbonyl group is

  1. CH3COOCH3
  2. CH3CONH2
  3. CH3COOCOCH3
  4. CH3COCl
AIPMT 2010 (Prelims)
8

Propionic acid with Br2/P yields a dibromo product. Its structure would be

  1. [figure]
  2. CH2(Br)-CH2-COBr
  3. [figure]
  4. CH2(Br)-CH(Br)-COOH
AIPMT 2009
9

A strong base can abstract an α-hydrogen from

  1. ketone
  2. alkane
  3. alkene
  4. amine
AIPMT 2008
10

The relative reactivities of acyl compounds towards nucleophilic substitution are in the order of

  1. Acid anhydride > Amide > Ester > Acyl chloride
  2. Acyl chloride > Ester > Acid anhydride > Amide
  3. Acyl chloride > Acid anhydride > Ester > Amide
  4. Ester > Acyl chloride > Amide > Acid anhydride.
AIPMT 2008
11

Acetophenone when reacted with a base, C2H5ONa, yields a stable compound which has the structure

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2008

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