Benzotriazole CAS 95-14-7

The o-Phenylenediamine method is the most classic method for synthesizing benzotriazole, which includes the normal-pressure synthesis method of o-phenylenediamine and the improved high-pressure method of o-phenylenediamine.

1. o-Phenylenediamine normal pressure method: first dissolve o-phenylenediamine in acetic acid aqueous solution, and configure about 40% sodium nitrite aqueous solution; the two solutions are pre-cooled to 1-5 °C, mixed and reacted, and kept at In the ice bath, rapidly heat up to 80°C to close the ring to generate benzotriazole, cool and filter, wash with water to obtain the crude product; be distilled at an absolute pressure of 2000Pa, collect the fraction at 201～204°C, obtain the product with benzene crystallization, and collect the product. The rate is 70% to 80%. At present, most domestic manufacturers use this method. However, this method has the disadvantages of high toxicity of o-phenylenediamine, consumption of a large amount of acetic acid, difficulty in product purification, low yield and harsh reaction conditions. From the 1970s to the 1970s, many improvements were made to the above process, which improved the product yield.

   Later, Joseph of the United States switched to the method of dropping an aqueous solution of sodium nitrite, and the initial reaction temperature was increased to 55-60 °C. The reaction mixture was extracted with mixed amyl alcohol, distilled under a pressure of 266.6Pa, and the fractions at 157-170 °C were collected. Cooling, filtering and drying can obtain nearly colorless benzotriazole, and the yield can reach 96%. This method is easy to control the temperature and eliminates the ice bath that is not conducive to industrial production. The mixture after the reaction is extracted with hexanol, and the extraction process is carried out. Add polyethylene glycol 200 to the liquid, first recover hexanol by vacuum distillation, and then azeotropically steam out the polyethylene glycol solution of benzotriazole under the pressure of 266.6Pa. This improvement not only makes benzotriazole The yield increased to 95.1%, and the risk of decomposition and explosion of benzotriazole in vacuum distillation was reduced. The former West German Rochat used potassium nitrite instead of sodium nitrite, and in the presence of xylene and acetic acid, the reaction temperature was 20 ~ 50 ℃, the yield can reach 97%.

2. o-Phenylenediamine high-pressure method: The o-phenylenediamine high-pressure method was invented by John in the United States. The molar ratio of o-phenylenediamine to sodium nitrite is 1:1 to 1.05, the reaction temperature is 200 to 300°C, and the pressure It is 4.8×106～6.9×106Pa. After the reaction is completed, the pH value is adjusted to 6 with acid. Since no acid is involved in the diazotization ring-closure reaction, the chance of generating dark-colored tars by diazotization coupling is reduced, thereby improving the product. At the same time, the purification of the product becomes easy. For example, o-phenylenediamine is reacted with 37% aqueous sodium nitrite solution at a temperature of 260 ° C and a pressure of 3.0 × 106 to 3.3 × 106 Pa. After 3 hours of reaction Cooling, the pH value is adjusted from 11.7 to 6 with concentrated sulfuric acid to obtain benzotriazole with a purity of 100% and a yield of 96.9%. This process does not require acetic acid, with few side reactions, little pollution, high yield and reaction time Short, continuous production. Chinese researchers have successfully synthesized benzotriazole by one-step pressurization. Sodium benzotriazole is synthesized from o-phenylenediamine and sodium nitrite in one step by pressurization, and then acidified and crystallized to obtain the product. The cost of this method is reduced by 50% to 70%, and two domestic blanks are filled.

Benzimidazolone and sodium nitrite aqueous solution were reacted at 190 ° C under high pressure for 75 minutes, acidified, washed with water, and dried to obtain a product yield of 85.3%. Since benzimidazolone is prepared by the reaction of o-phenylenediamine and urea, Therefore, it is expensive, which restricts the application of this synthesis method.

O-nitrophenylhydrazine was reacted in ammonia water, isopropanol and hexanediol mixed aqueous solution at 140 ° C and high pressure for 1.5 hours to generate 1-hydroxybenzotriazole (HBTA). Copper-chromium trioxide was used as a catalyst , hydrogen and nitrogen were introduced in a ratio of 92:8, deoxygenation and hydrogenation were carried out at 160-170 ° C and high pressure for 1 hour, HBTA was deoxygenated and hydrogenated to form BTA, and the final yield of benzotriazole was 89%.

First, HBTA is directly synthesized from o-nitrochlorobenzene and hydrazine hydrate, and then deoxygenated and hydrogenated to form BTA. The highest total yield can reach 98.6%. The advantages of this method are high yield and few intermediate links. It is a promising and very important method.