Reaction of Aromatic Compounds MCQ - Practice Questions with Answers

A group which accumulates positive charge during resonance is said to show +M effect. And a group which accumulates negative charge during resonance is said to show -M effect.
We can see that the group showing(+M) effect donates the electron density whereas the group showing (-M) effect withdraws the electron density towards it. For example, Nitrobenzene is an electron-withdrawing group and hence it takes the electron density towards it. Thus it shows (-M) effect.

Reduction of Aromatic compounds
Reduction of the aromatic compounds is not easy as they are very stable due to their aromaticity and hence they have high resonance energy. So, we need to supply a greater amount of energy to reduce them.

For example:

The birch reduction is an organic reaction which is used to convert aromatic compounds into cyclohexadienes. In this reaction, organic reduction of aromatic rings in liquid ammonia with sodium, potassium or lithium and alcohol occurs.

Mechanism

For example

Benzene is unreactive towards even strong oxidising agents such as KMnO₄/K₂Cr₂O₇. However, in drastic conditions, it can be oxidised slowly to CO₂ and H₂O. It can undergo combustion reaction to give luminous and smoky flame.

1. Controlled oxidation with air: Benzene on oxidation with air at 773 K in presence of V₂O₅ as catalyst gives Maleic anhydride.
   
2. Oxidation of Alkyl benzene: Alkyl groups when attached to the benzene ring, they are easily oxidised by an alkaline solution of potassium manganate.