Question

Luminol, which is used by forensic scientists to find blood, fluoresces as a result of Diels-Alder like process. The dianion of luminal reacts with to form an unstable peroxide intermediate that then loses nitrogen to form a dicarboxylate and emit light. The process is similar to that in 14-21 and 14-22. Propose a mechanism for this process.

Short answer

First,a non conjugated diene is formed as a result of the reaction of diene and dienophile. This non-conjugated diene, by loosing from it, will give dicarboxylate given.

Step-by-step solution

Diels-Alder reaction

Diels-Alder reaction was discovered by the German chemists Otto Diels and Kurt-Alder in 1928 for which they got Nobel prize 1950.

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 (bond breaking and bond formation occur simultaneously. Diels alder reaction is used to generate 6 membered rings.

Diene and dienophile

Diene is an organic compound which comprises of two conjugated pi bonds (4 pi bonds) while dienophile is a diene loving compound containing 2 pi electrons. When the interaction between them, occurs a transition state without any additional energy barrier, is obtained.

Here, the diene is

while the dienophile is

Mechanism    

First of all, the Diels-Alder reaction of given diene and dienophile generates a product in which double bonds are not conjugated.

Diels-Alder reaction

so a more stable product can be formed by the loss of on heating.