Which of the following statements about the mechanism of the diels-alder reaction is
true?
a) three pi bonds break; two sigma bonds and one pi bond form.
b) three pi bonds break; one sigma bond and two pi bonds form.
c) two pi bonds break; one sigma bond and one pi bond form.
d) two pi bonds break; two sigma bonds and one pi bond form.

A) Three pi bonds break; two sigma bonds and one pi bond form.

Explanation:

Diels Alder reaction -

It is one of the chemical reaction , where the reaction of a substituted alkene and a conjugated diene takes place , is referred to as the diel alder reaction .

Where the substituted alkene is referred to as the dienophile .

Hence , it is also known as diene - dienophile reaction.

The mechanism followed by the reaction is same as for pericyclic reaction , in this reaction , there is breakage of three pi bond and the formation of one pi an two sigma bond.