NMR.‐Investigation of the Formaldehyde Addition and Oligomerisation Equilibria in the System Formaldehyde/Water/Acetic Acid/Hydrochloric Acid

Abstract

Summary. -An NMR. investigation of the state of formaldehyde in acidic solutions has been carried out. Solutions of DCl/D,O/CD,COOD containing two sources of formaldehyde, i. e. paraformaldehyde (I) and trioxane (TI), were used for this purpose. In systems I and I1 the effect of various D,O/CD,COOD ratios, at a constant DC1 concentration, was studied, while for I1 the effect of changing DC1 concentration was also investigated. The results show that in aqueous solution, formaldehyde exists primarily as the monomeric and linear oligomeric forms of methylene glycol. Reducing the amount of D,O (at constant DC1 concentration), while increasing the CD,COOD content, results in an increase in the polymeric species and in trioxane. I n addition, substitution of water by acetic acid results in systems that are catalytically more active than aqueous solutions of the same hydrochloric acid concentration. Along with the usual polymer-monomer equilibria which exist in such solutions, side reactions of methylene glycol with the hydrochloric acid present also occur to a small extent, e.g. acetylation, substitution of OH by C1 and the Cannizzaro reaction. It is suggested that these findings will result in a better understanding of the formaldehyde crosslinking reactions in cotton cellulose.

Acidities of Hydrochloric Acid in Water/Acetic Acid and in Water/Acetic Acid/Formaldehyde Mixtures: Investigations with the indicator method and with the nmr method. 31st communication on investigations in textile chemistry

“…Potentially it could be concluded from the relation between the d values of Table 7 and the water content that water molecules are used for methylene glycol formation (HOCH,OH) from CH,O and paraformaldehyde [HO-(CH,O),-HI. This conclusion is, however, not substantiated by the investigation mentioned [12] : There it was shown that methylene glycol formation decreases with lower water contents of the systems used.…”

“…As shown in a previous communication [12], formaldehyde is involved in a multiplicity of complex addition and oligomerisation equilibria in systems containing water, acetic acid and hydrochloric acid. Potentially it could be concluded from the relation between the d values of Table 7 and the water content that water molecules are used for methylene glycol formation (HOCH,OH) from CH,O and paraformaldehyde [HO-(CH,O),-HI.…”

Identification of Di(oxymethylene)glycol in the Raman Spectrum of Formaldehyde Aqueous Solutions by ab Initio Molecular Dynamics Simulations and Quantum Chemistry Calculations

“…1 H and 13 C NMR analysis of the solutions has proven to be a powerful tool to analyze the species present in the solutions. − Raman spectroscopy − and IR spectroscopy have been less successful due to the complexity of the spectra. In a previous paper, we addressed the question of the spectroscopic properties of methanediol in aqueous solutions, using a combined approach of ab initio molecular dynamics (MD) simulations and anharmonic quantum chemistry calculations, taking explicitly into account the H-bonded water molecules.…”

“…The amount of the different oligomers in the solutions depends on the temperature, the initial formaldehyde concentration, and possibly the pH. 5 1 H and 13 C NMR analysis of the solutions has proven to be a powerful tool to analyze the species present in the solutions. 9−16 Raman spectroscopy 17−20 and IR spectroscopy 21 have been less successful due to the complexity of the spectra.…”