What is the pH condition for the reaction of urea and formaldehyde to produce polyhydroxymethylurea?
Thread Content
Recently, I have been trying to carry out a reaction between urea and formaldehyde to produce polyhydroxymethylurea, and then adding sodium p-aminobenzenesulfonate to facilitate polymerization and thus obtain a high-molecular-weight polymer. I have tried this several times but have not been able to obtain the desired final product. After analysis, it seems that the reason might be that the reaction between urea and formaldehyde did not result in the formation of polyhydroxymethylurea. Therefore, I would like to ask experts: what are the conditions required for the reaction between urea and formaldehyde to produce polyhydroxymethylurea? Is a catalyst and other conditions required for the second step of polymerization with sodium p-aminobenzenesulfonate? I carried out the second polymerization reaction by heating to 85 degrees Celsius under alkaline conditions.
For the first step, try a temperature of around 60 degrees
Urea and formaldehyde can undergo the following reactions: NH2C O N H2 + HCHO → NH2CONHCH2OH (monohydroxymethylurea); NH2CONHCH2OH + HCHO → HOCH2NHCONHCHOH (dihydroxymethylurea). When a solution of monohydroxymethylurea is acidified, an exothermic reaction occurs to form methylenem urea: NH2CONH2 + HOCH2NHCONH → —— + H2O. Specific structural forms of methylenem urea include NH2CONHCHNHCONH2 (methylenediurea), NH2CONHCH2NHCONHCH2NHCONH2 (dimethylenetriurea), and NH2CONH(CH2NHCONH)n (polymethylenem urea), where n = 1 to 8–10.
Keeping the solution system alkaline prevents the formation of methylenurea.