• 072920 77839
  • info@smartachievers.in

Topic Question Set

Q 1 :    

Methyl group attached to a positively charged carbon atom stabilizes the carbocation due to          [2024]

  • –I inductive effect

     

  • electromeric effect

     

  • hyperconjugation

     

  • mesomeric effect

     

(3)

Alkyl groups directly attached to the positively charged carbon stabilise the carbocations due to hyperconjugation effect.
Example: CH3CH2+ (ethyl cation) in which the positively charged carbon atom has an empty p-orbital. One of the C—H bonds of the methyl group can align in the plane of this empty p-orbital and the electrons constituting the C—H bond in plane with this p-orbital can then be delocalised into the empty p-orbital.

This type of overlap stabilises the carbocation because electron density from the adjacent σ bond helps in dispersing the positive charge.

Q 2 :    

The most stable carbocation among the following is               [2024]

 

  •  

  •  

  •  

  •  

(4)

3° Carbocations are more stable than 1° and 2° carbocations due to hyperconjugation and +I effect.

 

Q 3 :    

Given below are two statements:
Statement I: In an organic compound, when inductive and electromeric effects operate in opposite directions, the inductive effect predominates.
Statement II: Hyperconjugation is observed in o-xylene.

In the light of the above statements, choose the correct answer from the options given below:            [2023]

  • Statement I is true but Statement II is false.

     

  • Statement I is false but Statement II is true.

     

  • Both Statement I and Statement II are true.

     

  • Both Statement I and Statement II are false.

     

(2)

 

Q 4 :    

A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following?          [2020]

  • –I effect of –CH3 groups

     

  • +R effect of –CH3 groups

     

  • –R effect of –CH3 groups

     

  • Hyperconjugation

     

(4)

 

Q 5 :    

The most stable carbocation, among the following is:              [2019]

  • (CH3)3C-C+H-CH3

     

  • CH3-CH2-C+H-CH2-CH3

     

  • CH3-C+H-CH2-CH2-CH3

     

  • CH3-CH2-C+H2

     

(3)

Among the given carbocations,

CH3-C+H-CH2-CH2-CH3 is most stable carbocation. As it consists of maximum number of α-hydrogens and stablised by hyperconjugation.

 

Q 6 :    

Which of the following carbocations is expected to be most stable?          [2018]

  •  

  •  

  •  

  •  

(3)

-NO2 group is meta-directing, thus will stabilize a electrophile at m-position.

 

Q 7 :    

The correct statement regarding electrophile is             [2017]

  • electrophile is a negatively charged species and can form a bond by accepting a pair of electrons from another electrophile

     

  • electrophiles are generally neutral species and can form a bond by accepting a pair of electrons from a nucleophile

     

  • electrophile can be either neutral or positively charged species and can form a bond by accepting a pair of electrons from a nucleophile

     

  • electrophile is a negatively charged species and can form a bond by accepting a pair of electrons from a nucleophile.

     

(3)

 

Q 8 :    

Which of the following statements is not correct for a nucleophile?            [2015]

  • Ammonia is a nucleophile.

     

  • Nucleophiles attack low e- density sites.

     

  • Nucleophiles are not electron seeking.

     

  • Nucleophile is a Lewis acid.

     

(4)

Nucleophiles are electron rich species hence, they are Lewis bases.

 

Q 9 :    

Treatment of cyclopentanone  with methyl lithium gives which of the following species?         [2015]

  • Cyclopentanonyl radical

     

  • Cyclopentanonyl biradical

     

  • Cyclopentanonyl anion

     

  • Cyclopentanonyl cation

     

(3)

 

Q 10 :    

Which of the following is the most correct electron displacement for a nucleophilic reaction to take place?         [2015]

  •  

  •  

  •  

  •  

(1)

Nucleophile will attack a stable carbocation (SN1 reaction).