What is nitration of benzene?
Nitration of benzene is a Aromatic electrophilic substitution reaction. Benzene is highly stable to electrophilic substitution. It is absolutely true, it is highly attractive to electrophile. Nitration of benzene is form nitrogroup (NO2).
Nitration of benzene is given nitrogroup (NO2). When hydrogen atoms on the benzene ring is replaced by a nitrogroup (NO2). This is called nitration of benzene.
In other words, hydrogen atoms of benzene ring is converted in to Nitronium ions, this phenomenon is called nitration of benzene.
When benzene is treated with a mixture of construction nitric acid (HNO3) and construction of sulphuric acid (H2SO4). It is given nitrobenzene. As shown in figure
In both figure, construction HNO3 act as a catalyst and H2SO4 act as a reagent. as shown in figure.
After reaction it give Nitronium ions (NO2+)
Nitric acid is interacted with sulphuric acid and then it produce electrophile.
Nitric acid (HNO3) and sulphuric acid (H2SO4) both are interacted each other and it give Nitronium ion (NO2+). and after reaction, finally nitrobenzene product are formed.
In this case,
HNO3 – pre-electrofile
H2SO4 – electrophile maker
NO2 – making electrophile
We know that,
HNO3 is week acid and
H2SO4 is strong acid,
When the strong acid H2SO4 is react with week acid HNO3 then it work as a acid and base.
H2SO4 work as a acid (strong acid) whereas
H2SO4 work as a base (week acid).
Mechanism of nitration of benzene
The mechanism for nitration of benzene is in three steps. the electrophilic substitution reaction of benzene is completed with the help of three steps.
1. Generation of electrophile
2. Electrophile will attack the Benzene ring
1.Generation of electrophile
When nitric acid (HNO3) react with sulphuric acid (H2SO4) to form NO2+ , HSO4 and H2O (water molecule), as as shown in figure.
the interaction of nitric acid (HNO3) and sulphuric acid (H2SO4) is produced electrophile. This is also called Nitronium ions (NO2+)
C6H6-NO2 or nitrobenzene
Nitronium ions (NO2+)
In other words;
Benzene is treated with the nitrating mixture which is the combination of construction of nitric acid and construction of sulphuric acid to give nitrobenzene. nitration of benzene is electrophilic substitution reaction. and one of the hydrogen atoms persent on the benzene ring.
2. Electrophile will attack on the benzene ring,
When the electrophile will attack on the benzene ring then you need to write the structure of benzene ring. Which is an electrophile is easy to electron dificiance, therefore, in the benzene ring they should be negative charge (-).
To generate the negative charge, π electron move to particular position on the benzene ring. as a result electron density produce and combine that carbon item with the electrophile. then as a results nitrobenzene product is formed as shown in figure.
We have got this intermediate which is + charge.
In benzene structure, all the position, there are hydrogen atoms but one particular position of benzene ring, it make bond and +charge occurs on the particular position.
So, this steps is required deprotonation.
In this case, the – negative charge of HSO4 (-) is interacted with H+ positive charge to form H2SO4 and final nitrobenzene product is formed as shown on figure.
What is Sulphonation of benzene?
Sulphonation of Benzene:
Sulphonation of benzene are addition of Sulphonic group (SO3H) to benzene. For example;
When benzene is react with fuming sulphuric acid in the presence of H2SO4 then it give benzene sulphonic acid, (C6H6+SO3H) as shown in figure.
fuming sulphuric acid is also be written as (H2SO4+SO3).
This reagent can also be used in this reaction. Because the meaning of both reagent are same.
When benzene is react with the help of this reagent it produces benzene sulphonic acid as a product.
Mechanism of sulphonation of benzene
Generation of electrophile
In this case, when fuming sulphuric acid react with SO3 then it give electrophile (HSO4+) and HSO4 – both are formed as a product.
Where, HSO4+ is called electrophile (E+).
It is easy to generate electrophile (E+) by fuming sulphuric acid.
Attack of electrophile on benzene
In this case, first reaction of electrophile (HSO4+) are attack on benzene ring and it release (H+) as shown in figure.
Benzene are always electrophilic attack and release (H+) as shown in the reaction.
Regeneration of Catalyst
In this reaction, finely sulphuric acid of first step and H+ of second step is react each other then it give fuming sulphuric acid. You know that,
H2SO4 – regenerated and
Use identity is SO3.
When benzene add with oleum or fuming sulphuric acid then it give benzene sulphonic acid.