Synthesis of 2-(2′-hydroxy-5′-methylphenyl)benzotriazole-N-oxide

2-(2′-hydroxy-5′-methylphenyl)benzotriazole-N-oxide was synthesized from azo-compound with hydrazine hydrate as a reducing agent.The effect of the molar ratio of reactants,the amount and concentration of sodium hydroxide on the product was studied.Experimental results showed that,the best molar ratio of azo-compound,hydrazine hydrate and sodium hydroxide is 1∶0.53∶5.3,the concentration of sodium hydroxide was 18%,and the reaction temperathre was from 80 to 82℃,under above conditions the reaction yield could be higher than 95% with the purity of products up to 99%.