Furan-Synthesis-Reactivity-Reactions

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Furan
Furan

Synthesis:

a) Oat hulls, rice hulls and corncobs contain pentosan which on treatment with hot hydrochloric acid gets converted into furfural. When furfural is decomposed in steam at 400oC in the presence of oxide catalyst, furan is obtained.

Preparation of Furan from oat hulls, rice hulls and corncobs

b) It can also be synthesized from mucic acid.

Synthesis of furan from mucic acid

Reactivity:

Furan is a monocyclic planar molecule with (4n + 2)Π system.

Resonating structure of Furan

Furan is less aromatic than thiophene and pyrrole , probably due to the strong electronegative character of the O atom, which draws the Π-cloud much towards itself .

Chemical properties:

a)Although furan is an aromatic compound, yet it shows a few properties of conjugated dienes.

Furan undergoes Diel-Alder reaction with maleic anhydride.(which pyrrole and thiophene does not)

Furan undergoes Diel-Alder reaction with maleic anhydride

b)Furan is catalytically reduced to tetrahydrofuran.

Preparation of tetrahydrofuran

c)Oxidation of furan gives succinaldehyde. In presence of acids, resinification occurs.

Oxidation of furan

d)As furan is labile to the action of acids, nitration is done by acetyl nitrate, sulphonation by SO3/Pyridine.

Nitration and sulphonation of furan

e)As direct halogenations of furan gives polymer, it is prepared indirectly via mercuration or from furoic acid.

Halogenation of furan

f)Friedel Craft alkylation of furan leads to polymerization. But it can be acylated in presence of SnCl4 catalyst(As AlCl3 attack the furan it is not used). It can also be acylated via mercuration.

Alkylation and acylation of Furan

g)Formylation of furan is done by Gattermann reaction

Formylation of furan

h)When an alkaline solution of furan is treated with benzenediazonium salts, 2-aryl furan is obtained.

2-aryl furan

i)When furan is treated with n-buytllithium, 2-lithiumfuran is obtained. Which when hydrolysed, furoic acid is formed.

furoic acid

j)Conversion of furan to pyrrole, pyridine,Furoin, Furilic acid, furil.

Conversion of furan to pyrrole, pyridine,Furoin, Furilic acid, furil.