Kinetics of the formation of methylene linkages in solutions of urea and formaldehyde

A kinetic investigation is made of the reactions between monomethylol urea, dimethylol urea and urea in acid aqueous solution. Strong indications are obtained that these reactions are all of one type viz. bimolecular hydrogen ion catalyzed reactions between an amidomethylol group and an amide group, leading to the formation of methylene linkages between urea fragments: magnified image The rate constant of this reaction appeared to depend on the type of amide group or amidomethylol group that are reacting. The activation energy is about 15 kcal/mole. The reaction between two molecules of dimethylol urea was found to be very slow if occurring at all. The formation of cyclic structures by trimerisation of monomeric methylene urea and the formation of dimethylene ether linkages between urea fragments may be excluded.