NMR study on furfurylalcohol‐formaldehyde equilibrium systems

Abstract

Equilibrium reactions in the beginning of the process of furfurylalcohol-formaldehyde resin-production have been studied. Based on 'Hand I3C-NMR analysis the components of the system have been quantitatively determined. Equilibrium constant values of the simultaneous reactions have been calculated. ZUSAMMENFASSUNG:Gleichgewichtsreaktionen zu Beginn der Reaktion zwischen Furfurylalkohol und Formaldehyd wurden untersucht. Auf Grund von ' Hund I3C-NMR-Analysen wurden dieKomponenten des Systems quantitativ bestimmt. Gleichgewichtskonstanten der gleichzeitig ablaufenden Reaktionen wurden ermittelt.

Proton and carbon-13 nuclear magnetic resonance spectrometry of formaldehyde in water

“…In previous studies, a quantitative determination of different oligomers (3,5,10) was made possible on the assumption that the equilibrium constants of reactions involving the considered oligomers were constant. As pointed out by Kopf (6) from the results of a preliminary study at 313 K (W = 40%), K3 is significantly smaller than K2 (K3/K2 = 0.62 and 0.71 with methanol).…”

“…(3) Prasad, A. (10) Iyengar, G. V.; Kasperek, K.; Felndegen, L. E. Scl. A number of NMR studies, involving either 1H or 13C spectrometry, have been devoted to aqueous solutions of formaldehyde owing to the great industrial importance of this compound (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12).…”

“…(10) Iyengar, G. V.; Kasperek, K.; Felndegen, L. E. Scl. A number of NMR studies, involving either 1H or 13C spectrometry, have been devoted to aqueous solutions of formaldehyde owing to the great industrial importance of this compound (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12). In aqueous solutions, formaldehyde reacts with water to give methylene glycol which oligomerizes easily according to the following scheme: CH20 + H20 Fi hoch2oh HOCH2OH + HOCH2OH H0(CH20)2H + h2o HO(CH20)n-1H + HOCH2OH HO(CH20)"H + H20…”

“…The structures of the different species present in the solutions have already been determined, mainly by NMR (2)(3)(4)(5)(6)(7)(8)(9)(10)(11)(12), but no special attention has been paid to the influence of temperature on the oligomeric distribution nor to the chemical relaxation rate of dilution, i.e., the time required for the solution to reach equilibrium when the concentration is changed. On the other hand, the quantitative determination of oligomers in solutions, which is performed by gas chromatography (GC), necessitates the substitution of the labile hydrogens by a trimethylsilyl group, and one might expect the distribution measured by GC to be perturbed by this chemical treatment.…”

“…Table II. Methods for Drying Biological Tissue Samples method associated problems thermal oven high temperatures cause loss of volatile elements and alteration of sample matrix (10) 16-72 h needed to dry samples (10) microwave oven for effective drying samples must be minced (9), internal high temperature effects probable freeze-drying sample contamination from the metallic freezer housing (esp. Cr) is possible (11), cellular integrity destroyed dry ashing high temperatures result in a loss of elements such as As, Co, Cr, and Ni by volatilization (12)(13)(14)(15)(16)(17) wet ashing loss of Se, Te, and Po and matrix interferences due to incomplete destruction of the organic matrix when samples are treated with HN03/HC10" or H2S04/H202 (12,18), possible sample contamination from reagents used in the procedure (19)(20)(21)(22)(23)(24)(25)(26)(27) elemental losses due to volatilization were held at an absolute minimum by keeping the drying chamber and its contents at ambient temperature and at atmospheric pressure.…”