Comparison of advantages and disadvantages of several synthesis methods of Luminol

Luminol is a chemiluminescent reagent. Among the many chemiluminescent reagents, luminol reagents have high luminescence quantum yield and good water solubility, and can chemically react with various oxidants and have become The most widely used chemiluminescent reagent. Its luminescence mechanism is that of oxidative reaction. They are catalyzed by horseradish peroxidase under alkaline conditions and oxidized by hydrogen peroxide to produce their excited intermediates that return to aminophthalic acid. When they return to the ground state, they emit Photon. Therefore, Luminol reagents have good application value and broad market demand prospects. The advantages and disadvantages of several Luminol synthesis methods are briefly described here.

The current method of preparing luminol mainly has the following synthetic routes:

(1) Using 3-nitrophthalic acid as a raw material, it undergoes a cyclization reaction with hydrazine hydrate, and is reduced with an insurance powder to obtain luminol (J. Chem. Educ., 1934, II: 142～145). This synthetic method has a simple process route, but the disadvantages are: 1. The reaction temperature in the first step is high, requiring 225 degrees; 2. The purification is difficult. The first step requires the use of high-boiling substance triethylene glycol as a solvent, which is difficult to remove. The reducing agent safety powder used in the second step will decompose during the reaction to produce several inorganic impurities, which are difficult to remove; 3. The yield is low, only about 30%.

(2) Using 3-nitrophthalic acid as a raw material, it undergoes a cyclization reaction with hydrazine sulfate, and is reduced with an insurance powder to obtain luminol (Org. Synth. 1949, 29, 78 and Org. Synth. 1949, 29, 8). The synthesis method has made some improvements on route one, but the disadvantages are: 1. The highly toxic hydrazine sulfate is used; 2. The reaction temperature in the first step is 170 degrees, the temperature is too high, and the equipment requirements are high; 3. The reaction produces a lot of The waste liquid and the reducing agent safety powder used in the second step will decompose during the reaction to produce several inorganic impurities, which are difficult to remove.

(3) Monophthalic anhydride is used as the raw material to nitrate with mixed acid to obtain 3-nitrophthalic acid, dehydrate with acetic anhydride to obtain 3-nitrophthalic anhydride, then hydrazine decompose, and finally reduce iron powder Get Lumino. The shortcomings of this synthesis method are: 1. Long synthetic route; 2. Mixed acid nitrification, which generates a large amount of acidic waste liquid; 3. Iron powder reduction, a large amount of iron slag waste, and greater environmental pollution.

Another method of synthesizing luminol or isoluminol using the one-pot method has obvious advantages and beneficial effects compared with the prior art.

1) The method realizes the completion of the three-step reaction in the same pot, without any purification treatment of the intermediate product, and finally obtains the product directly.

2) The method has simple synthesis route, mild reaction conditions, simple operation, and the required reagents are all conventional reagents, and the required equipment is conventional equipment, so the price is low, therefore, the cost required for synthesis is low, suitable for industrial large-scale production .

3) The yield and purity of luminol and isoluminol synthesized by this method are high. The yield of luminol and isoluminol are both above 80%, and the purity of HPLC is above 98%, which can fully meet the industrialization of products. Production and market demand.