Lance Feig
CH 128L
Luminol Report
Purpose
The purpose of this experiment was to synthesize luminol and then perform a chemiluminescence reaction. First, 3-nitrophthalic acid was reacted with hydrazine to generate 3-nitrophthalhydrazide, which is a cyclic diamide. The conversion of a carboxylic acid functional group to an amide function group is reversible and produces water. To drive the reaction to the amide product, the reaction was performed at 300 ˚C to evaporate the water product, which is an application of Le Chatelier’s principle. Second, the aromatic nitro group was reduced to an amine using sodium dithionite. The reaction is given in Figure 1.
Figure 1: Synthesis of luminol from 3-nitrophthalic acid and hydrazine.
To verify the synthesis of luminol, the product was mixed with an oxidant (diluted bleach) and was inspected for a blue glow. Chemiluminescence is a process by which light is generated by a chemical reaction. The excited state of the product drops to the ground electronic state while emitting the energy difference in the form of a photon. In the mechanism for luminol chemiluminescence, it has been proposed that
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After the second centrifugation, the top liquid was discarded, then sodium hydroxide and deionized water were added. The solution was mixed and transferred to an Erlenmeyer flask, cooled, then mixed with the bleach solution. Although solid was present in the tube, only a small quantity was present and it was wedged into the bottom tip of the conical tube. It is highly probable that when the Falcon tube was mixed, the luminol was not dissolved, so it would be left behind after decantation. This would leave little to no luminol in the supposed luminol-containing flask. Combined with the extremely dilute bleach, this could explain the lack of blue