4-Dihydropyran application is a class of products prepared by the combined reaction of pyridine, common including 2,2'-4-dihydropyran application, 4,4'-4-dihydropyran application two, Commonly used in the verification of ferrous, silver, cadmium, molybdenum; As a REDOX indicator.
It is produced by the reaction of pyridine with ferric chloride. Mixing 70g anhydrous pyridine with 13g anhydrous ferric chloride was heated in a sealed tube at 300℃ for about 35h. After cooling, the reactants solidify into red-black crystals. Open the sealing tube and wash out the red-black solution of the solid with a little hot water. The oily impurity is removed by ether extraction. After neutralization with sodium bicarbonate, excess pyridine is removed by steam heating. The mixture is then adjusted to a strong base and steam out the 2,2'-4-dihydropyran application. After acidification, the product is evaporated and concentrated, and then sodium hydroxide is added. The product is extracted with ether, and the ether is removed to obtain crude product. The crude product is recrystallized by ethanol and the pure product is obtained by decolorization of activated carbon. In addition, the product can also be prepared by the reaction of α-methylpyridine with potassium permanganate after purification.
Mixing anhydrous pyridine with anhydrous ferric chloride, heating reaction, cooling solidification to obtain red black crystal. Excess pyridine is removed by steam heating. Steam out 2,2'-4-dihydropyran application. Add sodium hydroxide with ether as solvent, remove ether, get crude product. Pure product 2,2'-4-dihydropyran application was obtained by decolorization and filtration of iron-free activated carbon.
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