Benzene to benzoic acid-Gattermann-Koch reaction
Benzene to benzoic acid change
There are different way for the preparation of benzoic acid from benzene molecule . The well known process is, involving Friedel craft’s alkylation or acylation reaction.
Benzoic acid can be prepared from benzene molecule , converting it first methyl benzene or toluene by Friedel craft’s alkylation reaction.
In the second step, oxidation of this toluene molecule by potassium permanganate followed by acidic hydrolysis ,produced the expected benzoic acid .
There are many other methods for the preparation of benzoic acid from benzene molecule.
For example , benzoic acid can be prepared from benzene , converting it Grignard reagent’s .
In the first step, benzene reacts with bromine in presence of iron catalyst , it form bromo benzene .
This bromo benzene reacts with metallic magnesium in dry ether medium , changed into Grignard reagent , phenyl magnesium bromide .
Finally, phenyl magnesium bromide reacts with carbon dioxide followed by hydrolysis , gives the expected product , benzoic acid .
Again , benzoic acid can be prepared from benzene , converting it acetophenone in the first step by Friedel craft acylation .
Then ,in the second step,this acetophenone under goes haloform reaction, that is chloroform reaction to produce chloroform and sodium benzoate .
The acidic hydrolysis of this sodium benzoate gives benzoic acid .
One more change of benzene to benzoic acid through nitration of benzene . Nitration of benzene, followed by reduction , gives aniline .
This aniline under goes diazotization reaction to form diazonium salt .
On sand meyer’s reaction of diazonium salt in presence of CuCN / KCN , gives cyano benzene , which on acidic hydrolysis finally produce benzoic acid .
Gattermann-Koch reaction .
Besides the above reactions, the another most important name reaction ,Gattermann-Koch aldehyde synthesis ,through which benzoic acid may be prepared.
When a mixture of carbon monoxide and hydrogen chloride is passed through benzene
solution in presence of anhydrous AlCl3 and little amount of Cu2Cl2 catalyst , then benzaldehyde is obtained as the main product .
This reaction is known as Gattermann-Koch aldehyde synthesis .The solvent used in this reaction is nitrobenzene or ether .
On oxidization of this benzaldehyde by oxidizing agent ,the expected benzoic acid is obtained .