Hydrochloric Acid → Carbendazim

Participants

Reaction Conditions

Reaction Steps

To a jacketed reactor equipped with feed ports stirrer, reflux condenser, and pH probe are added 32 parts of 50% cyanamide solution and 100 parts of water. Methyl chloroformate (41.1 parts) and 67 parts of 50% sodium hydroxide solution are changed concurrently so as to maintain the pH of the solution at 7 - 7.5 and the reacton temperature at 40° - 50° C. The solution is held at 50° C. for 45 minutes and then 36 parts of o-phenylenediamine is added. The pH of the solution is held at 3.9 to 4.1 by the gradual addition of 65 parts of 37% HCl. The solution is heated to 105° C. and held at this temperature for 30 minutes. During this hold time, the product starts to crystallize. The reaction mass is cooled to 25°-30° C. and the solid product is filtered, washed with water and acetone, and dried in the vacuum oven at 80° C. to give 59.6 parts of 2-benzimidazolecarbamic acid, methyl ester. This represents a product yield of 93.5% based on o-phenylenediamine.

Provenance & Evidence