Question: Convert : 1.) Phenyl Cyanide from Benzene 2.) Phenol from Toluene...

Question

Convert :
1.) Phenyl Cyanide from Benzene
2.) Phenol from Toluene

Answer 1

Solution

There are many paths by which benzene can be converted into phenyl cyanide. It may involve first substitution of methyl group on benzene ring and then its oxidation and then further conversion with use of reagents. Similarly, toluene can be oxidised first and then converted into phenol.

Complete Solution :
There are many methods of formation of phenyl cyanide from benzene.
Benzene is an electron rich compound. It is resonance stabilised , so it can not undergo addition reactions because addition will lead to destroy of resonance. But it undergoes electrophilic substitution reactions where one Hydrogen is substituted by any other group.
The reaction for benzene to phenyl cyanide is as-

But it requires a series of steps to give this product.

The steps involved are -
The first step involves the Friedel Crafts alkylation reaction in which methyl chloride and $AlC{l_3}$ are used to convert benzene into toluene.

Then, the Toluene is converted to benzoic acid by acidifying Potassium dichromate. The reaction is as -

This benzoic acid is then converted into benzamide by reaction of benzoic acid with ammonia as-

Then, this benzamide is reduced by phosphorus pentoxide to give phenyl cyanide, our desired product. The reaction can be given as -

The second reaction is conversion of toluene to phenol. This reaction can be written as -

- It also involves two steps that are as-
The first step is conversion of toluene to benzaldehyde by reaction with $Cr{O_2}C{l_2}$ . This reaction is written as-

The second step is the reaction of benzaldehyde with hydrogen peroxide and sodium hydroxide to produce phenol that is our desired product.

Note: The conversion of toluene to benzaldehyde by use of reagent $Cr{O_2}C{l_2}$ is termed as Etard reaction. This reaction is used to produce benzaldehyde for many purposes. The reaction of benzaldehyde with hydrogen peroxide and sodium hydroxide is named as Dakin reaction. It is commonly used to prepare phenol.