NUCLEOPHILIC SUBSTITUTION REACTION

Which of the following compound shows the correct decreasing order of solvolysis with aqueous ethanol?

• III > II > I > IV

• III > II > IV > I

• II > III > IV > I

• III > I > IV > II

Answer explanation

The solvation of above compound can be compared by this trend, i.e. Solvation trend: 3^O halide > 2^O halide > 1^O halide > vinylic halide

Which of the following reaction will go faster if the concentration of the nucleophile is raised?

• I & II

• I & III

• I & IV

• III & II

Answer explanation

I & II reaction undergo via SN2

​ mechanism. III & IV reaction undergo via SN1

​ mechanism. The rate of reaction in SN2​ reaction is directly proportional to the concentration of nucleophile.

. Which one is an excellent substrate for SN2 reaction?

• 
• 
• 
• 

Answer explanation

Alpha-halo carbonyl undergoes fastest SN₂ reaction due to the coupling of π* of CO bond and π* of C–X bond.

Arrange the compounds in increasing order of the rate of reaction towards nucleophilic substitution.

• (a) < (b) < (c)

• (c) < (b) < (a)

• (a) < (c) < (b)

• (c) < (a) < (b)

Arrange the compounds in increasing order of the rate of reaction towards nucleophilic substitution.

• (a) < (b) < (c)

• (b) < (a) < (c)

• (c) < (b) < (a)

• (a) < (c) < (b)

Which of the following compounds will give racemic mixture of nucleophilic substitution by OH− ion?

• I

• I,II,III

• II,III

• III

Answer explanation

To exhibits racemic mixture the compound should contain at least one chiral carbon in the compound.∗ Chiral carbon is an asymmetric carbon that is attached to four different types of atoms or group of atoms.∗ But all other compound didn't have at least one chiral.

Reaction of C6H5CH2Br with aqueous sodium hydroxide follows ____________.

• SN1 mechanism

• SN2 mechanism

• Any of the above two depending upon the temperature of the reaction

• Saytzeff rule

Answer explanation

C6H5CH2 MOST STABLE CARBOCATION

• i < iii < ii

• i < ii < iii

• iii < iii < i

• ii < i < iii

Which of the following undergoes aromatic nucleophilic substitution at fastest rate?

• 
• 
• 
• 

In SN1 reaction on optically active substrate gives

• retention in configuration

• inversion in configuration

• racemic mixture

• no product