Which of the following undergoes nucleophilic substitution exclus

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 Multiple Choice QuestionsMultiple Choice Questions

231.

Addition ofwater to alkynes occurs in acidic medium and in the presence of Hg2+ ions as a catalyst. Which of the following products will be formed on addition of water to but-1-yne under these conditions?

  • CH3CH2CH2CHO

  • CH3CH2COCH3

  • CH3CH2COOH

  • CH3COOH + HCHO


232.

Which one of these is not true for benzene?

  • It forms only one type of mono-substituted product

  • There are three carbon-carbon single bonds and three carbon-carbon double bonds

  • Heat of hydrogenation of benzene is less than its theoretical value

  • The bond angle between carbon-carbon bonds is 120°


233.

CH3CHO +HCHO HeatDil. NaOH A H3O+HCN B

The structure of compound B is


234.

Which of the following statement is correct ?

  • +I group stabilises a carbocation

  • +I group stabilises a carbanion

  • -I group stabilises a carbocation

  • -I group stabilises a free radical


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235.

Which of the following can give a Grignard reagent when reacted with magnesium in dry ether?

  • C2H6

  • C2H5Cl

  • C2H5OH

  • C2H5CN


236.

t-butyl chloride preferably undergo hydrolysis by

  • SN1 mechanism

  • SN2 mechanism

  • Any of (a) and (b)

  • None of these


237.

Iodoform gives a precipitate with AgNO3 on heating but chloroform does not because

  • C - I bond in iodoform is weak and C - Cl bond in chloroform is strong

  • chloroform is covalent

  • iodoform is ionic

  • None of the above


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238.

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

  • Benzyl chloride

  • Ethyl chloride

  • Chlorobenzene

  • lsopropyl chloride


A.

Benzyl chloride

Among all the given options, benzyl chloride undergoes SN1 mechanism.

Aliphatic SN1 reaction is carried out in two steps:

(i) carbonium (carbocation) ion is formed and its formation is based upon the stability.

Stability order of carbocation- 

C6H52C+H2 > CH3C+H - CH3 > CH3C+H2

(ii) Nucleophile is attracted towards the carbonium ion in form of fast step to give final product.

Hence, in benzyl chloride, ethyl chloride and isopropyl chloride order of SN 1 reaction is benzyl chloride > isopropyl chloride > ethyl chloride


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239.

Which of the following organic halogen compounds undergoes hydrolysis with aqueous NaOH predominantly by Sy1 mechanism?

  • Ethyl iodide

  • Methyl chloride

  • lsopropyl chloride

  • Benzyl chloride


240.

Under basic condition which one suffers elimination the most?

  • (CH3)3CCI

  • (CH3)2CHCH2CI

  • CH3CH2CHCICH3

  • CH3CH2CH2CH2CI


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