Luminol Essay

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CHM 238 TITLE: Luminol PURPOSE: The purpose of this experiment was to synthesize luminol (5-aminophthalhydrazide) from 3-nitrophthalic acid and observe the energy transfer to a fluorescent dye. As a big picture, the purpose of the experiment was to demonstrate how a chemical process can lead to a photochemical outcome though the synthesis of luminol. DISCUSSION: In part A of the experiment, 3-nitrophthalic acid reacted with hydrazine forming 5-nitrophthalhydrazide, a cyclic diamide. The solvent used in this reaction was triethylene glycol, which allowed for the dehydration of hydrazonium salt. The nitro group of 5-nitrophthalhydrazide was reduced with a mild reducing agent, sodium dithionite, in part B. At the end of part B, yellow crystals of 5-Aminophthalhydrazide were collected. By adding a strong base (NaOH), luminol was converted to a dianion, which formed peroxide when oxidized by molecular oxygen. Dimethylsulfoxide was used as a solvent in the previous reaction. The bond between the two oxygen atoms in peroxide is relatively weak; unstable peroxide decomposes producing nitrogen gas and 3-aminophthalate dianion. Electronically exited state of the dianion ultimately releases energy in the form of light by emitting a photon. Light emission resulted from the conversion of chemical energy into light energy due to changes in the composition of the chemiluminescent material. Thus, light production is related to the electronic state of the molecule. If an electron is promoted to an orbital of higher energy, it is no longer paired. Luminol is a precursor for an intermediate in the triplet state (unpaired parallel spins) that produces light through fluorescence. The intermediate that emits light has been identified as the excited state singlet (unpaired opposite spins) of the 3-aminophthalate dianion. Different colors observed in part C of the
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