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Haloalkanes and Haloarenes · Question 27

AIPMT 2010 (Prelims)MCQEasy📈 Topic in 50% papers+4−1
1

Which one is most reactive towards SN1 reaction?

  1. C6H5CH(C6H5)Br
  2. C6H5CH(CH3)Br
  3. C6H5C(CH3)(C6H5)Br
  4. C6H5CH2Br

Answer

(3) C6H5C(CH3)(C6H5)Br

Solution

SN1 reactivity depends on the stability of the carbocation formed.

(3) gives C6H5 +C(CH3)(C6H5), a tertiary carbocation stabilised by resonance with two phenyl rings and by hyperconjugation of CH3.

(1) gives a secondary diphenylmethyl cation, (2) a secondary benzylic cation and (4) a primary benzylic cation – all less stable.

(3) is the most reactive towards SN1.

Answer: (3)

AIPMT 2010 (Prelims)

Keep practising — Haloalkanes and Haloarenes

2

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)
3

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
4

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2009
5

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
6

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

  1. Ethyl chloride
  2. Isopropyl chloride
  3. Chlorobenzene
  4. Benzyl chloride
AIPMT 2005
7

Which of the following is least reactive in a nucleophilic substitution reaction?

  1. (CH3)3C-Cl
  2. CH2=CHCl
  3. CH3CH2Cl
  4. CH2=CHCH2Cl
AIPMT 2004
8

Chloropicrin is obtained by the reaction of

  1. steam on carbon tetrachloride
  2. nitric acid on chlorobenzene
  3. chlorine on picric acid
  4. nitric acid on chloroform
Out of syllabusAIPMT 2004
9

Reactivity order of halides for dehydrohalogenation is

  1. R-F > R-Cl > R-Br > R-I
  2. R-I > R-Br > R-Cl > R-F
  3. R-I > R-Cl > R-Br > R-F
  4. R-F > R-I > R-Br > R-Cl
AIPMT 2002
10

An organic compound A (C4H9Cl) on reaction with Na/diethyl ether gives a hydrocarbon which on monochlorination gives only one chloro derivative, then A is

  1. t-butyl chloride
  2. s-butyl chloride
  3. iso-butyl chloride
  4. n-butyl chloride
AIPMT 2001

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