Diels- Alder question about number of products

[stgt9202]

So I just took a practice test in which there is a reaction between cyclopentadiene and maleic anhydride and part of the question asked if there would be two products or one. In the passage it said that a diels alder reaction is first order and it is concerted....but with this particular reaction don't you technically get two products (exo and endo)? the answer said that there was one product. Do we take into account the endo and exo products for Diels-Alder for the MCAT or is that too in depth?

Thanks a bunch!

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[jmbusclas]

So I just took a practice test in which there is a reaction between cyclopentadiene and maleic anhydride and part of the question asked if there would be two products or one. In the passage it said that a diels alder reaction is first order and it is concerted....but with this particular reaction don't you technically get two products (exo and endo)? the answer said that there was one product. Do we take into account the endo and exo products for Diels-Alder for the MCAT or is that too in depth?

Thanks a bunch!

Did the passage tell you whether or not you were under kinetic or thermodynamic control? If not, you should assume normal conditions with no heat (kinetic).

In this specific reaction, the endo product is formed first under normal conditions. This is due to the fact that the dienophile contains those good sp2 hybridized electron withdrawing groups. The endo product allows for constructive, in-phase overlap of the respective p-orbitals. Under normal conditions you will obtain the endo product virtually exclusively.

If the passage were to state that this reaction was indeed under thermodynamic control, then you would account for the exo product.