Abstract
N''-Cyanoguanidine (CG) is hydroxymethylated with formaldehyde, then condensed and polymerized into resinous products under acidic conditions. These resinous products are useful as commercial flocculants. However, little has been reported the bimolecular condensates having methylene linkage and their formation pathways, partly because the reaction is complicated with the simultaneous structural conversion of CG into diaminomethyleneurea (DU). The bimolecular condensates from CG and formaldehyde (the given mole ratio of formaldehyde/CG = 1/ 2) under various conditions and the products from DU and formaldehyde were analyzed by HPLC, 1H-NMR spectrometry and FD-MS spectrometry in order to elucidate their structures and the formation pathways. When formaldehyde is introduced to the amino groups of CG before the hydration of the cyano group, bis (N''-cyanoguanidino) -methane is produced, eventhough the highest yield is as low as ca. 20%. On the other hand, when the hydration precedes the hydroxymethylation, formaldehyde is introduced to the amino group of newly formed carbamoyl group of DU, thus N, N′-methylene bis [N′- (diamino methylene) urea] being produced in ca. 90% yield. The other four condensates may be possible to be produced to the varying amounts, eventhough their yields may be low or trace. The composition of the bimolecular condensates is affected by the reaction conditions, especially by the concentration of acids.
