Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Haloalkanes and Haloarenes question

2019 · 12 Apr · Shift 2 · Q21
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Chemistry
  4. /Haloalkanes and Haloarenes
  5. /2019 · 12 Apr · Shift 2 · Q21

Haloalkanes and Haloarenes question

2019 · 12 Apr · Shift 2 · Q21

JEE MainChemistryHaloalkanes and HaloarenesMCQ+4 / −1
An 'Assertion' and a 'Reason' are given below. Choose the correct answer from the following options : Assertion (A) : Vinyl halides do not undergo nucleophilic substitution easily. Reason (R) : Even though the intermediate carbocation is stabilized by loosely held p-electrons, the cleavage is difficult because of strong bonding.
  1. A
    Both (A) and (R) are correct statements but (R) is not the correct explanation of (A)
  2. B
    Both (A) and (R) are correct statements and (R) is the correct explanation of (A)
  3. C
    (A) is correct statement but (R) is a wrong statement
  4. D
    Both (A) and (R) are wrong statements.
View written solutionFree

Correct answer: C

  1. Evaluate the Assertion (A)

    Assertion: Vinyl halides do not undergo nucleophilic substitution easily.

    Vinyl halides have the halogen attached directly to an sp2sp^2sp2-hybridized carbon of a double bond, e.g. CH2=CHClCH_2=CHClCH2​=CHCl.

    They do not undergo nucleophilic substitution easily because:

    • The C−XC-XC−X bond is stronger than in alkyl halides.
    • Due to resonance, the C−XC-XC−X bond acquires partial double bond character.
    • SN1SN1SN1 is difficult because formation of a vinylic carbocation is highly unstable.
    • SN2SN2SN2 is difficult because backside attack at an sp2sp^2sp2 carbon is not favorable.

    Hence, Assertion (A) is correct.

  2. Evaluate the Reason (R)

    Reason: Even though the intermediate carbocation is stabilized by loosely held p-electrons, the cleavage is difficult because of strong bonding.

    This statement is incorrect.

    For vinyl halides:

    • The carbocation that would form in an SN1SN1SN1 process is a vinylic carbocation, which is not stabilized; in fact, it is highly unstable.
    • The second part, that cleavage is difficult because of strong bonding, is correct in spirit, but the statement as a whole is wrong because it incorrectly claims carbocation stabilization.

    Therefore, Reason (R) is wrong.

  3. Choose the correct option

    • (A) is correct
    • (R) is wrong

    So the correct option is: C\boxed{C}C​

PreviousNext

More from Haloalkanes and Haloarenes

  • Which one of the following is likely to give a precipitate with AgNO3​ solution ?2019 · MCQ
  • Heating of 2-chloro-1-phenylbutane with EtOK/EtOH gives X as the major product. Reaction of X with Hg(OAc)2​/H2​O followed by NaBH4​ gives Y as the major product. Y is :2019 · MCQ
  • The major product in the following conversion is – Includes diagram2019 · MCQ
  • The major product of the following reaction is : Includes diagram2018 · MCQ
  • The most polar compound among the following is :2018 · MCQ
  • The major product of the following reaction is: Includes diagram2018 · MCQ
  • The major product of the following reaction is : Includes diagram2017 · MCQ
  • The major product of the following reaction is : Includes diagram2017 · MCQ