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The urea-formaldehyde (UF) reaction under strong alkaline condition was investigated by using quantitative analysis of 13C NMR. The main reaction products were methylolureas and oligomers linked by ether bonds at the beginning stage. With the reaction undergoing, the methylene linkages began to be formed and become predominant at the end point. The conversion of linear methylene ether bond to methylene linkage was also observed. These features were also observed previously for the reaction under acidic condition. It was found that the cyclic ether structure (uron) is much more stable than the linear ether bond, and its stability is second only to the methylene linkages among all the condensed structures. The formaldehyde was consumed in fast Cannizarro reaction under strong alkaline condition, producing considerable amount of methanol, which is the main negative aspect of this condition. With the exception of the differences caused by Cannizarro reaction, the UF production reactions under alkaline and acidic conditions are similar. The pH did not change the thermodynamic nature of the involved reactions, but only changed the competitive relationships of different reactions in kinetics. [ABSTRACT FROM AUTHOR]

The reaction between urea and HO- in alkaline solution was investigated at B3LYP and MP2 levels. The PCM solvent model was used to include the implicit solvent effects. To estimate the specific solvation effects, explicit water molecules were added stepwise to form molecular clusters. The results show that the OH- anion can abstract a proton from urea, forming the urea anion. The calculated energies indicate the hydrogen bonds formed between the reactants and solvent water molecules affect both the potential and thermodynamic energy barriers. The changing trend of the barriers appears to be 1W > 2W > 3W > 0W. A fast equilibrium can be established between the reactants and the products but the reverse reaction is both kinetically and thermodynamically more favourable, suggesting that the concentration of urea anion in alkaline solution would be low, in agreement with known weak acidity. The results of this study suggest that for reaction systems involving strongly polar reactants and solvent, the employment of only implicit solvent model is not enough, and explicit solvent molecules must be included. [ABSTRACT FROM AUTHOR]

To find the effects of cross-linker phenol-formaldehyde (PF) resin on the performance of soy-based adhesives, the reaction between model compounds hydroxymethyl phenol (HPF) and glutamic acid were studied in this paper. HPF prepared in laboratory conditions showed higher content of hydroxymethyl groups than normal PF resin, which was proved by the results of Electrospray Ionization Mass Spectrometry (ESI-MS) and 13C Nuclear Magnetic Resonance (13C-NMR). The results of ESI-MS, Fourier transform infrared spectroscopy (FT-IR), and 13C-NMR based on resultant products obtained from model compounds showed better water resistance of the soy protein-based adhesive modified by PF-based resin, which indicated the reaction between PF resin and soy protein. However, it seemed that the soy-based adhesive cross-linked by HPF with the maximum content of hydroxymethyl groups did not show the best water resistance. [ABSTRACT FROM AUTHOR]