Equilibrium
Speciation in Moderately Concentrated
Formaldehyde–Methanol–Water Solutions Investigated Using <sup>13</sup>C and <sup>1</sup>H Nuclear Magnetic Resonance Spectroscopy
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Abstract
We used <sup>13</sup>C and <sup>1</sup>H 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
