Org. Chem II Experiment 9 Synthesis of Luminol - OChemOnline

Org. Chem II Experiment 9 Synthesis of Luminol 2
In neutral solution, luminol exists largely as a dipolar ion (zwitterion). This dipolar ion exhibits a
blue fluorescence after being exposed to light. However, in alkaline solution, luminol is
converted into its dianion.
NH 3
O
NH 2
O
C
C
N
NH
C
N
+ 2 OH + H 2 O
N
C
luminol
O
O
The dianion of luminol undergoes a reaction with molecular oxygen to form peroxide of
unknown structure. This peroxide is unstable and decomposes with the evolution of nitrogen gas,
producing the 3-aminophthalate dianion in an electronically excited state.
NH 2
O
NH 2
O
*
C
C
N
N
C
O
+ O ? 2
+ N 2
O
C
O
O
The excited dianion emits a photon, which is observed as visible light.
NH 2 O
*
NH 2 O
C
O
O
C
O
O
+ hν
C
C
O
O
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