Q 14-14-63 E - Organic Chemistry (Mcmurry)

Question

Dimethyl butynedioate also undergoes a Diel-Alder reaction with (2E, 4Z)-2,4-hexadiene, but the stereochemistry of the product is different from that of the (2E,4E) isomer (Problem 14-62). Explain.

Step-by-Step Solution

Answer

Diels-Alder reaction

Diels-Alder reaction is an important organic reaction which includes a substituted alkene in the form of a dienophile and a conjugated diene. It proceeds via concerted mechanism (simultaneous bond breaking and bond formation). Diels alder reaction generates a 6 membered ring.

It is a pericyclic reaction between a conjugated diene and a dienophile. The reaction is stereospecefic i.e., the cis dienophile will give cis stereochemistry in product and trans dienophile will generate product with trans stereochemistry.

Diene and dienophile

Diene is an organic compound which comprises of two or more double bonds separated by a single bond while dienophile is a diene loving compound or ( a substituted alkene with electron withdrawing group). When the interaction between them, occurs a transition state without any additional energy barrier, is obtained.

Diels-Alder reaction of Dimethyl butynedioate and (2E,4Z)-2,4-hexadiene

                                              Diels-Alder reaction

The product obtained from the reaction of Dimethyl butynedioate and (2E,4Z)-2,4-hexadiene Differs from that of of Dimethyl butynedioate and (2E,4E)-2,4-hexadiene at the carbon marked star in the product, since in Diels –Alder reaction stereochemistry of both diene and dienophile is retained.