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Proof of ether-bridged condensation products in UF resins by 2D NMR spectroscopy |
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| Authors: | Éléonore J Kibrik Oliver Steinhof Günter Scherr Werner R Thiel Hans Hasse |
| Affiliation: | 1. Laboratory of Engineering Thermodynamics, University of Kaiserslautern, Erwin-Schr?dinger-Strasse 44, 67663, Kaiserslautern, Germany 3. Laboratory of Thermodynamics and Thermal Process Engineering, University of Stuttgart, Pfaffenwaldring 9, 70550, Stuttgart, Germany 4. BASF SE, GMU/C, 67056, Ludwigshafen, Germany 2. Department of Chemistry, University of Kaiserslautern, Erwin-Schr¨odinger-Strasse 54, 67663, Kaiserslautern, Germany |
| Abstract: | The existence of ether-bridged condensation products in urea-formaldehyde (UF) resins is still disputed in the literature as these products have never been isolated or fully characterized. Using 1H-15N gradient heteronuclear single quantum correlation (gHSQC) experiment, 1H-13C gHSQC experiment and 1H-13C gradient heteronuclear multiple bond correlation (gHMBC) experiment a, methylolurea hemiformal compound (urea compound with oligomeric chains $-\rm{CH}_{2}{\rm OCH}_{2}{\rm O]}{\mathrm {n}}{\rm H}$ and $n\geq 1$ ) and a symmetrical compound, most likely an ether-bridged condensation product, in a UF resin sample were characterized. The results were confirmed by 2D NMR 13C-13C gradient correlated spectroscopy (gCOSY) experiment using 13C labeled ureaformaldehyde samples. Spectroscopic chemical shifts of the proposed ether-bridged condensation product in 15N, 13C, 1H NMR spectroscopy were assigned. Furthermore, individual peak assignments are provided for the methylolurea hemiformal moiety. |
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