Diels-alder reaction

Question

could someone explain this

Answer 1

a alkene with an electron withdrawing group reacts with a conjugated diene to form a cyclohexene ring with very little energy needed.

Answer 2

The Diels-Alder reaction(DA reaction) is the most common way for an organic chemistry to make cyclic compounds.

The DA reaction is a pericyclic concerted reaction that proceeds through the simultaneous movement of 6 pi electrons.

The most common example is the 4+2 cycloaddition of the diene, 1,4-butadiene and the dieneophile, ethylene, to make the product cyclohexene.

If you number the carbon atoms on the diene as 1 2 3 4 where the double bond is between carbon atoms 1 and 2

And you number the carbon atoms of dieneophile 5 and 6.

The pi electrons from C1 and C2 move in between C2 and C3

The pi electrons from C3 and C4 attack C5 to make a new single bond.

The pi electrons from C5 and C6 attack C1 to make a new single bond.

This overall reaction is deemed to be very thermodynamically favorable due the expense of breaking two pi bonds to make two new single bonds which are much stronger.

If it's difficult to picture the mechanism have a look at this.

http://www.chemhelper.com/dielsalder.htm...