LUMINOL'S REACTION [10, 11]
The luminol's chemiluminescence manifests with emission of light when it comes oxidized to 3-aminoftalic acid with H2O2. The basic reaction is given below.
Mechanism of the Reaction
3-aminophthalhydrazide combines with a basic solution, which removes the hydrogen protons from the nitro groups to release two water molecules. A catalyst decomposes the hydrogen peroxide (or other oxidizing molecule).
The resulting molecule undergoes keto-enol tautomerization to move the negative formal charges onto the carbonyl oxygens.
The oxygen next performs a cyclic addition to the two (previously) carbonyl carbons. Nitrogen is an excellent leaving group because its own
bonds are so strong (and as a gas, it is entropically favoured too)
so the charge on the oxygens come back down to form carboxylate anions by expelling nitrogen gas. This leaves 3-APA*.