Question

Why does furan undergo Diels alder reaction?

Answer 1

Hint : Diels alder reaction is a typical example of a pericyclic reaction with a slightly complicated process or mechanism. Diels alder reaction can be defined as the chemical reaction in the organic chemistry between dienophiles.

Complete Step By Step Answer:
So, basically Diels alder reaction is the reaction between the substituted alkene and the conjugated diene, this is known as dienophile and the product of this reaction is a substituted cyclohexene derivative.
Now let’s discuss the structure of the furan for a better understanding of the reaction.
So furan is a heterocyclic organic compound consisting of five aromatic rings. Each ring contains one oxygen atom and four carbon atoms.
Furan is an aromatic compound because one of its lone pairs of electrons that are present on the oxygen atom becomes delocalised into the ring creating a system similar to benzene.
Furan serves as a diene in Diels–Alder reactions with electron-deficient dienophiles such as ethyl (E)-3-nitroacrylate. And the product formed upon reaction is a mixture of endo-isomers.
Furans represent aromatic systems like benzene but they are much less resonance stabilised as compared to benzene.
However when the process is energetically favourable the aromatic $\pi$ system of the furans gets disturbed. Thus these furans acts as a diene in the presence of dienophile and undergoes Diels alder reaction quickly.

Note :
However furan is a colourless and flammable compound. It is known to be volatile in nature. And it has a boiling point near to the room temperature. It is also non-toxic in nature. So the compound containing these furan rings are known as furans.