Equilibrium speciation in moderately concentrated formaldehyde−methanol−water solutions investigated using 13C and 1H nuclear magnetic resonance spectroscopy

We used 13C and 1H NMR spectroscopy to examine the equilibrium speciation in formaldehyde−methanol−water solutions at moderate formaldehyde concentrations such as those used in the synthesis of formaldehyde-based organic gels. Concentrations of small methylene glycol oligomers and their methoxylated forms found in these solutions were quantitatively determined over a range of formaldehyde concentrations and methanol−water ratios, and at temperatures between 10 and 55 °C. Using the measured concentrations, equilibrium constants for methylene glycol dimer and trimer formation as well as methoxylation of these oligomers were calculated. Based on this, we developed a quantitative equilibrium model for calculation of formaldehyde-related species concentrations over a range compositions relevant for formaldehyde based sol−gel processes allowing for more rational design of formaldehyde polymerization systems.