Phosphoric Acid → O-Phenylenediamine

Participants

Reaction Conditions

Reaction Steps

170 g (1.5 mols) of caprolactam and 215 g (2 mols) of o-phenylene diamine are melted in a nitrogen atmosphere. 10 g of 85 % by weight phosphoric acid (the remaining 15 % by weight being water) are run into the melt with stirring, at 100°C and the heating is continued, 28 g of water distilling off over a period of 2 hours at an internal temperature of 170 to 250°C. The reaction mixture is then subjected to fractional distillation, initially in a water jet vacuum and subsequently in an oil pump vacuum. After the first distillate of excess o-phenylene diamine, 247 g (81 % of the theoretical) of 2-(5'-aminopentyl)-benzimidazole are obtained in the form of a yellowish-brown solidifying in crystalline form with a boiling point of 210° to 215°C at 0.05 Torr, and a melting point of 101°C.

Provenance & Evidence