E.i. Dupont De Nemours and Company

Tzu-Ching Chang

Lynn E Applegate

Patti Ann Parziale

Process for preparing 2-(4-thiazolyl)-1H-benzimidazole (generic name: thiabendazole) by the acid-catalyzed condensation of o-phenyldiamine and 4-cyanothiazole in solution in water or mixtures of water with miscible co-solvents (solvents which upon mixing with water in all proportions form a homogeneous mixture, as well as, other partially miscible solvents which upon mixing with water in some proportions form a homogeneous mixture under the reaction conditions of the process of this invention).

Process for preparing thiabendazole

A process of separating amines having different basicity constants is disclosed. The more reactive amine is converted to a salt which is extracted with water in a multiple stage countercurrent extractor. The salt form of the amine is converted to the free amine. In a preferred aspect of the invention the amine salt is an amine sulfite which can be converted to free amine and sulfur dioxide. The sulfur dioxide can be reused to generate more amine sulfite. The more reactive amine is then separated from the water and part of it recovered. The remainder of the more reactive amine is recycled to the countercurrent extractor. The less reactive amine is removed from the countercurrent extractor in the free amine state as an organic phase along with any organic solvent that is used. Part of the less reactive amine is recovered from the system while the remainder is converted to a salt and an aqueous solution thereof recycled to the countercurrent extractor.

Separation of amines by preferential aqueous salt extraction

An acid extraction process for separating 3,4-dichloroaniline from 2,3-dichloroaniline and 2,5-dichloroaniline is disclosed. The process involves selectively forming 3,4-dichloroaniline hydrochloride, since it has a higher basicity than the other dichloroaniline isomers, in a multiple stage extraction unit. An aqueous solution of 3,4-dichloroaniline hydrochloride is removed from the multiple stage extraction unit and neutralized with a base to form an immiscible mixture of an aqueous salt solution and 3,4-dichloroaniline which are separated by decantation.

Growing community of inventors

Wilmington, DE, United States of America

Tzu-Ching Chang