1

### JEE Main 2018 (Online) 15th April Evening Slot

On treatment of the following compound with a strong acid, the most susceptible site for bond cleavage is :

A
Cl $-$ O2
B
O2 $-$ C3
C
C4 $-$ O5
D
O5 $-$ C6

## Explanation

Here the lone pair of electrons on O2 is involved in resonace with C = C.
So,   O2 will not be protonated.

The lone pair electrons of O5 is not involved in resonance with any C = C. So, O5 can be protonated.

When we use strong acid like HCl then chloride ion will attack least substituted C atom (C6).

2

### JEE Main 2018 (Online) 16th April Morning Slot

The most polar compound among the following is :
A
B
C
D
3

### JEE Main 2019 (Online) 9th January Morning Slot

Arrange the following amines in the decreasing order of basicity :

A
I > II > III
B
III > I > II
C
III > II > I
D
I > III > II

## Explanation

Baric nature depends on the tendency of donating the lone pair.

In (I) st amine lone pair of N atom is not in resonance. So it can easily donate the lone pair.

In (II) amine lone pair of N atom is in resonance. So, lone pair is not available.

In (III) amine lone pair of N atom is not in resonance so lone pair can be easily donated.

So, (I) and (III) are more baric compare to (II).

In (I) amine N atom is connected to sp2 hybridised carbon atom and in (III) amine N atom is connected to sp3 hybridised carbon atom.

We know sp2 carbon atom has more $-$ I effect than sp3 carbon atom.

So, in (I) amine density of electrons around N atom will decrease due to $-$ I effect and basic nature also decrease.

So, correct order of basic nature : III > I > II
4

### JEE Main 2019 (Online) 9th January Evening Slot

The increasing basicity order of the following compounds is :

A
A < B < D < C
B
D < C < A < B
C
D < C < B < A
D
A < B < C < D

## Explanation

(A) In the first compound, because of +I effect of CH3CH2- group electron density increses on N atom.

(B) In the second compound, because of +I effect of two CH3CH2- group electron density is more on N atom than first compound so it is more basic than compound A.

(C) Three -CH3 group creates steric hindrance around N atom, for that reason N atom can't donate lone pair easily.

(D) Here lone pair of N atom, perticipate in resonance with benzene ring so N atom can't donate lone pair. That is why it is least basic among this four compounds.

So correct order is D < C < A < B.