1

### JEE Main 2016 (Online) 10th April Morning Slot

The “N” which does not contribute to the basicity for the compound is :

A
N 7
B
N 9
C
N 1
D
N 3

## Explanation

In this aromatic compound, the lone of N9 is participate in resonance with the compound and complete the aromatic system. So this lone pair is delocalised and can not gain proton (H+)

When an atom is already part of $\pi$ bond then the lone pair of the atom can not participate in resonance. That lone pair is called localised lone pair.

Here in N1, N3 and N7 all the lone pairs are localised. As those lone pair do not participate in resonance so it can gain proton (H+) so those lone pair will increase the basicity of the compound.
2

### JEE Main 2017 (Offline)

Which of the following compounds will form significant amount of meta product during mono-nitration reaction?
A
B
C
D

## Explanation

Nitration takes place in presence of concentrated HNO3 + concentrated H2SO4.

In strongly acidic nitration medium, the amine is converted into anilinium ion (– NH3+ ); substitution is thus controlled not by – NH2 group but by – NH3+ group which, because of its positive charge, directs the entering group to the meta-position instead of ortho and para.
3

### JEE Main 2017 (Online) 9th April Morning Slot

Among the following compounds, the increasing order of their basic strength is :

A
(I) < (II) < (IV) < (III)
B
(I) < (II) < (III) < (IV)
C
(II) < (I) < (IV) < (III)
D
(II) < (I) < (III) < (IV)
4

### JEE Main 2018 (Offline)

The increasing order of basicity of the following compounds is :
A
(d) < (b) < (a) < (c)
B
(a) < (b) < (c) < (d)
C
(b) < (a) < (c) < (d)
D
(b) < (a) < (d) < (c)

## Explanation

Among all the given compounds the basic nature depends upon their tendency to donate the electron pair.

Because of +M effect of $-$NH2, lone pair will make $\pi$ bond and $\pi$ bond will go to $-$NH and electron density will increase at $-$NH.

Because of +M effect Basic nature of this will make compare to others as in other compounds there is no +M effect and +M effect has more power than other effect.

Here, in,

$-$CH3 has +I effect so in N $-$ C bond electron will move towards nitrogen, So electron density increase at nitrogen.

And alkayl group also has +I effect, so it will also increase electron density at nitrogen.

As electron density at nitrogen increases, so tendency to donate electron pair increases and basic nature also increases.

In those following,

double bond has ($-$ I) effect, it will decrease the availability of lone pair electron at nitrogen but at (b) double bond is closer to nitrogen, so ($-$ I) effect will be more powerful than compound at (a), so (b) will be less basic nature.

So, the order of basicity, c > d > a > b