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Haloalkanes and Haloarenes · Question 22

AIPMT 2011 (Mains)MCQEasy📈 Topic in 12% papers+4−1
1

Which of the following compounds undergoes nucleophilic substitution reaction most easily?

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

Answer

(1) [figure]

Solution

As per NCERT, the presence of an electron withdrawing group (–NO2) at ortho- and para-positions increases the reactivity of haloarenes towards nucleophilic substitution.

∵ The –NO2 group at the para-position withdraws electron density from the ring and stabilises the negatively charged (carbanion) intermediate by resonance.

–CH3 and –OCH3 are electron releasing groups; they destabilise the carbanion and decrease the reactivity below that of chlorobenzene.

∴ 1-Chloro-4-nitrobenzene undergoes nucleophilic substitution most easily.

Answer: (1)

AIPMT 2011 (Mains)

Keep practising — Haloalkanes and Haloarenes

2

Consider the reactions. (i) (CH3)2CH-CH2Br C2H5OH (CH3)2CH-CH2OC2H5 + HBr (ii) (CH3)2CH-CH2Br C2H5O- (CH3)2CH-CH2OC2H5 + Br- The mechanisms of reactions (i) and (ii) are respectively

  1. SN1 and SN2
  2. SN1 and SN1
  3. SN2 and SN2
  4. SN2 and SN1
AIPMT 2011 (Mains)
3

Which one is a nucleophilic substitution reaction among the following ?

  1. CH3-CH=CH2 + H2O H+ CH3- OH |CH-CH3
  2. RCHO + R'MgX R- OH |CH-R'
  3. CH3-CH2- CH3 |CH-CH2Br + NH3 CH3-CH2- CH3 |CH-CH2NH2
  4. CH3CHO + HCN CH3CH(OH)CN
AIPMT 2011 (Prelims)
4

In the following reaction C6H5CH2Br [2. H3O+]1. Mg, ether X, the product 'X' is

  1. C6H5CH2OCH2C6H5
  2. C6H5CH2OH
  3. C6H5CH3
  4. C6H5CH2CH2C6H5
AIPMT 2010 (Mains)
5

The reaction of toluene with Cl2 in presence of FeCl3 gives X and reaction in presence of light gives Y. Thus, X and Y are

  1. X = Benzal chloride, Y = o-chlorotoluene
  2. X = m-chlorotoluene, Y = p-chlorotoluene
  3. X = o- and p-chlorotoluene, Y = Trichloromethyl benzene
  4. X = Benzyl chloride, Y = m-chlorotoluene
AIPMT 2010 (Prelims)
6

Which one is most reactive towards SN1 reaction?

  1. C6H5CH(C6H5)Br
  2. C6H5CH(CH3)Br
  3. C6H5C(CH3)(C6H5)Br
  4. C6H5CH2Br
AIPMT 2010 (Prelims)
7

The correct order of increasing reactivity of [figure] C–X bond towards nucleophile in the following compounds is

  1. I < II < IV < III
  2. II < III < I < IV
  3. IV < III < I < II
  4. III < II < I < IV
AIPMT 2010 (Prelims)
8

Which of the following reactions is an example of nucleophilic substitution reaction?

  1. 2RX + 2Na R-R + 2NaX
  2. RX + H2 RH + HX
  3. RX + Mg RMgX
  4. RX + KOH ROH + KX
AIPMT 2009
9

Trichloroacetaldehyde, CCl3CHO reacts with chlorobenzene in presence of sulphuric acid and produces

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2009
10

In an SN2 substitution reaction of the type R-Br + Cl- DMF R-Cl + Br- which one of the following has the highest relative rate?

  1. CH3- CH3 | CH3 |C-CH2Br
  2. CH3CH2Br
  3. CH3CH2CH2Br
  4. CH3- CH3 |CH-CH2Br
AIPMT 2008
11

Which of the following undergoes nucleophilic substitution exclusively by SN1 mechanism?

  1. Ethyl chloride
  2. Isopropyl chloride
  3. Chlorobenzene
  4. Benzyl chloride
AIPMT 2005

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