Org. Chem II Experiment 9 Synthesis of Luminol 1
The production of visible light as a result of a low-heat-producing chemical reaction is called
chemiluminescence. A chemiluminescent reaction generally produces one of the product
molecules in an electronically excited state. The excited state relaxes to a lower energy state and
in the process emits a photon of visible light:
A* (excited) Æ A (relaxed) + hν
The light produced by fireflies and other bioluminescent organisms has fascinated observers for
many years. There are many different organisms that have developed the ability to emit light.
They include bacteria, fungi, protozoans, hydras, marine worms, sponges, corals, jellyfishes,
crustaceans, clams, snails, squids, fishes, and insects. Curiously, other than fish, this list does not
include many higher forms of life. The chemiluminescent compound in fireflies is called
luciferin. The enzyme, which induces it to emit light, is called luciferase.
In this experiment, the chemiluminescent compound luminol, or 3-aminophthalhydrazide, will be
synthesized from 3-nitrophthalic acid.
The first step of the synthesis is the simple formation of a cyclic diamide, 3-
nitrophthalhydrazide, by reaction of 3-nitrophthalic acid with hydrazine. Reduction of the nitro
group with sodium dithionite affords luminol.
NO2
C
C
3-nitrophthalic acid
+NH2
H2N
O
OH
OH
O
NO2
C
C
O
NH
O
NH
+ 2H2O
NO2
C
C
O
NH
O
NH
3-nitrophthalhydrazide
+ Na2S2O4+ 2H2O
NH2
C
C
O
NH
O
NH + 2NaHSO4
lu
m
inol
