2 2 4 4 Tetrahydroxybenzophenone CAS 131-55-5

2 , 4 – Dihydroxybenzoic acid and resorcinol generate 2 2 4 4 Tetrahydroxybenzophenone under the action of a catalyst (the reaction formula is as follows), which is a typical C-acylation reaction. C-acylation reaction is an important method for the preparation of aromatic ketones. It is an electrophilic substitution reaction that introduces acyl groups on aromatic hydrocarbons and their derivatives. It belongs to an important category of Friedel-Crafts reactions. Lewis acids or protonic acids must be added to the reaction. Catalyst to enhance the electrophilic ability of the acylating agent, so that the reaction can proceed smoothly. The commonly used acylating agents for C-acylation reactions are acid halides and acid anhydrides, followed by carboxylic acids. The catalyst can be BF3, ZnCl2 and other Lewis acids and concentrated H2SO4, H3PO4 polyphosphoric acid and other protonic acids. Its function is to enhance the positive charge on the acyl carbon atom and improve the electrophilic reaction ability of the attacking reagent.

In a 150 mL three-neck flask equipped with a stirrer and a hydrogen chloride absorption system, put 1510 g (0114 mol) of resorcinol, 1514 g (011 mol) of 2,4-dihydroxybenzoic acid, 2015 g (0115 mol) of anhydrous ZnCl2 mol), POCl3 3010 g (0.120 mol) and solvent cyclobutane 15 mL, start stirring, mix the materials evenly, heat up to 70 ℃ ~ 75 ℃, keep warm for 2 h, until little hydrogen chloride gas is released in the absorption system. Then slowly add water to the reaction bottle, stir until it is completely dissolved, then pour it into 800 mL of cold water, and fully dissolve. The above solution was left to stand for 30 min, cooled to below 20 °C, filtered with suction and washed with water to obtain the crude product. Then the crude product was dissolved in hot water, treated with activated carbon, boiled for 30 min, hot filtered, cooled, a large number of light yellow crystals were precipitated, filtered with suction, washed and dried to obtain 1617 g of yellow crystal product, yield 6719%, mp 198 °C ~ 200 °C. IR: υmax (cm- 1) :3 350～3 200 (b, s, υO – H), 1 629 (s, υC = O), 1 590 – 1 450 (s, υbenzene ring), 850～650 (s ,δ benzene ring-H).

The ultraviolet absorber 2,2′,4-trihydroxybenzophenone was synthesized by using resorcinol, o-hydroxybenzoic acid and oxytrichloride as raw materials, sulfolane as solvent and anhydrous zinc chloride as catalyst. Investigation The effects of reaction temperature, catalyst and material ratio on the reaction were studied. The results showed that the optimum conditions for the synthesis reaction were: reaction temperature 70-75℃, material ratio n(resorcinol):n(o-hydroxybenzoic acid ) was 1:0.81, the amount of POCl3 was 19 mL, and the anhydrous zinc chloride was 23 g. Under these conditions, a red powder solid was obtained, with a melting point of 188-190°C and a yield of more than 88%. The product passed elemental analysis, Infrared spectra were characterized.