Question

Explain Haworth synthesis of naphthalene.

Answer 1

Hint: There are five steps involved in the formation of naphthalene by Haworth synthesis. These are Friedel craft acylation, Clemmenson’s reaction, heating the compound, Clemmenson reaction, and dehydrogenation. Two aromatic rings joined are known as naphthalene.

Complete answer:
Naphthalene ${{C}_{10}}{{H}_{8}}$ is a simple, polycyclic aromatic hydrocarbon chemical molecule. It's a crystalline, white material with a distinctive smell. A fuse pair of benzene rings is the structure of Naphthalene. The constituent of traditional mothballs is best known.
The structure of naphthalene is given below:

The Haworth synthesis may be synthesized, the following stages are taken:
(i)- 3-benzoylpropionic acid is given via Benzene's craft acylation reaction with succinic anhydride.
(ii)- The second stage is the 3-benzoylpropionic acid reaction of Clemmenson, which results in 4-phenyl butanoic acid. Clemmensen reaction is observed in the presence of zinc amalgam and hydrochloric acid.
(iii)- The development of the ring structure of α-tetralene by elimination of the water molecule will result in this product being heated in the presence of strong sulphuric acid.
(iv)- Tetrahydronaphthalene is produced through the Clemmenson reaction of α-tetralene. Clemmensen reaction is observed in the presence of zinc amalgam and hydrochloric acid.
(v)- Tetrahydronaphthalene dehydrogenation produces naphthalene in the presence of selenium.
So, the reactions according to the steps are given below:

So, naphthalene is produced by Haworth synthesis by these steps.

Note:
Haworth synthesis is also used to produce other aromatic compounds like anthracene, phenanthrene, etc. Both anthracene and phenanthrene are aromatic compounds in which three benzene rings.