KINETICS ON COCONDENSATION BETWEEN PHENOL AND UREA THROUGH FORMALDEHYDE .1. PSEUDO-FIRST-ORDER REACTION OF MONOMETHYLOLPHENOL AND UREA

The kinetics of the reactions of methylolphenols and urea were investigated using 2- and 4-hydroxybenzyl alcohols. The high-performance liquid chromatography (HPLC) using a reverse phase column gave a clear separation between methylolphenols and hydroxybenzylureas. The molar ratios of hydroxybenzylureas to the corresponding methylolphenols in reaction mixtures were obtained from the ratios of peak areas of the chromatograms by using transfer factors corrected by quantitative C-13-NMR (carbon 13 nuclear magnetic resonance) measurements. The reactions of 2- and 4-hydroxybenzyl alcohols with excessive amounts of urea were found to follow the pseudo-first-order reaction. It was found that the pseudo-first-order rate constant for the formation of 4-hydroxybenzylurea is at least ten times greater than that of 2-hydroxybenzylurea. The reactivities of the two hydroxybenzyl alcohols also were investigated in terms of pH and kinds of acids used as catalysts. The pH dependencies of the pseudo-first-order rate constants were represented by linear equations in terms of hydrogen ion concentrations. It was found that the reactivity of 2-hydroxybenzyl alcohol is enhanced considerably by a zinc acetate/sulfuric acid system.