TBR Organic Chemistry Section IV Question 60?

[Godric]

I approached this problem by drawing the product out in my head, and then looking for sterocenters (so anything thats sp3 and has 4 differ groups attached to it) and I counted 2, and so the formula is 2^n and I got 4, but the answer key says 8, and I am not understanding why?

Did I overlook something, if so what, or was my way just completely wrong?
Thank you.

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[CodeRedDew]

The product that you have drawn is incorrect. You're missing an oxygen and an extra carbon. Secondly, the answer is 8 because the reaction forms two separate constitutional isomers along with the respective stereoisomers. Below is a photo of the two products, each of which have two stereocenters; therefore, according to the 2^n rule, each has four stereoisomers that can form. So 4+4 = 8!

 

[Godric]

The product that you have drawn is incorrect. You're missing an oxygen and an extra carbon. Secondly, the answer is 8 because the reaction forms two separate constitutional isomers along with the respective stereoisomers. Below is a photo of the two products, each of which have two stereocenters; therefore, according to the 2^n rule, each has four stereoisomers that can form. So 4+4 = 8!

Thanks for pointing my mistake out, I am not sure where I got the extra methyl from (might have just been exhausted at that point), and the missing methoxy group.
How did you know that the reaction would produce two constitutional isomers? When ever you preform a diels alder reaction, and the diene or dineophile are asymmetric, you can get multiple products (aka constitutional isomer)?

 

[grapepopsicle]

Yes, when the diene and dienophile are both asymmetrical, then there are two possible constitutional (or structural) isomers. The diene could have added either in the orientation in the picture, or upside down. Each of these would have two chiral carbons, so there would be 2 * (2^2) = 8 possible isomers.

 

[CodeRedDew]

Thanks for pointing my mistake out, I am not sure where I got the extra methyl from (might have just been exhausted at that point), and the missing methoxy group.
How did you know that the reaction would produce two constitutional isomers? When ever you preform a diels alder reaction, and the diene or dineophile are asymmetric, you can get multiple products (aka constitutional isomer)?

Lol happens to the best of us, especially when you're studying for hours at a time. And the post above me explains the answer to your question