The Kinetics of the Reaction of Formaldehyde with Ammonia

Abstract

The kinetics of the reaction of formaldehyde with ammonia to form hexamethylenetetramine has been investigated in dilute aqueous solutions at 20°C in the pH range between 6.3 and 11.9. The reaction was first-order with respect to ammonia and second-order with respect to formaldehyde. The rate increased sharply with the increasing pH to a maximum between 9 and 10, and then it decreased gradually. These results may be explained by a mechanism involving a rate-determining attack of methylolamine on free formaldehyde to form dimethylolamine, followed by the formation of hexamine through cyclotrimethylenetriamine and 1,5-endomethylene-1,3,5,7-tetrazacycloöctane.