Question

Cumene (isopropylbenzene) is a relatively inexpensive commercially available starting material. Show how you could prepare m-isopropylnitrobenzene from cumene.

Answer 1

Answer:

Nitration is a general chemical process for the introduction of a nitro group into a chemical compound through a chemical reaction.

Aromatic nitration occurs with aromatic compounds thanks to an aromatic electrophilic substitution mechanism that includes the attack of an electron-rich benzene ring by the nitronium ion.

Explanation:

Reaction mechanism

Cumene reacts with concentrated and hot nitric acid giving

m- isopropylnitrobenzene. The reaction has two drawbacks: it is slow and also the concentrated and hot nitric acid can oxidize any organic compound by an explosive reaction. A safer procedure is to use a mixture of nitric acid and sulfuric acid. Sulfuric acid acts as a catalyst, allowing the reaction to take place more quickly and at lower temperatures.

Sulfuric acid reacts with nitric acid generating nitronium ion (NO2 +), which is the electrophile of the aromatic electrophilic substitution reaction.

The nitronium ion reacts with cumene forming the sigma complex that loses a proton that is trapped by the bisulfate ion to give rise to m-isopropylnitrobenzene.

Nitration selectivity can be found by examining ring substituents and the effect they have on the reaction rate of this aromatic electrophilic substitution. Deactivation groups such as other nitro groups have a withdrawal effect of the electron pair that deactivates the reaction (creating difficulty in the formation of polynitrated products) and directs the electrophilic nitronium ion to attack the aromatic meta position.