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Haloalkanes and Haloarenes · Question 32

AIPMT 2005MCQMedium📈 Topic in 50% papers+4−1
1

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

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

Answer

(4) Benzyl chloride

Solution

As per NCERT, SN1 reactions proceed through a carbocation, so halides giving a very stable carbocation react by this path; allylic and benzylic halides show high reactivity towards SN1 because the carbocation is stabilised by resonance.

C6H5CH2Cl C6H5 CH2 + Cl (benzyl carbocation, resonance stabilised)

Ethyl chloride (1°) reacts by SN2; isopropyl chloride (2°) reacts by both SN1 and SN2; chlorobenzene does not undergo nucleophilic substitution under ordinary conditions (partial double bond character of C–Cl).

∴ Benzyl chloride undergoes substitution by SN1 mechanism.

Answer: (4)

AIPMT 2005

Keep practising — Haloalkanes and Haloarenes

2

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
3

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
4

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
5

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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