2787-01-1Relevant academic research and scientific papers
NOVEL GEMINI SURFACTANTS AND THEIR USE
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Paragraph 0114; 0115, (2015/06/18)
Disclosed herein are gemini surfactants, and methods for making and using these gemini surfactants. These gemini surfactants may be incorporated in paints and coatings to provide hydrophilic and/or self-cleaning properties. Surfactants are compounds composed of both hydrophilic and hydrophobic or lipophilic groups. In view of their dual hydrophilic and hydrophobic nature, surfactants tend to concentrate at the interfaces of aqueous mixtures; the hydrophilic part of the surfactant orients itself towards the aqueous phase and the hydrophobic part orients itself away from the aqueous phase.
Quantitative and qualitative 1H, 13C, and 15N NMR spectroscopic investigation of the urea-formaldehyde resin synthesis
Steinhof, Oliver,Kibrik, Eleonore J.,Scherr, Guenter,Hasse, Hans
, p. 138 - 162 (2014/04/03)
Urea-formaldehyde resins are bulk products of the chemical industry. Their synthesis involves a complex reaction network. The present work contributes to its elucidation by presenting results from detailed NMR spectroscopic studies with different methods. Besides1H NMR and13C NMR, 15N NMR spectroscopy is also applied.15N-enriched urea was used for the investigations. A detailed NMR signal assignment and a model of the reaction network of the hydroxymethylation step of the synthesis are presented. Because of its higher spectral dispersion and the fact that all key reactions directly involve the nitrogen centers,15N NMR provides a much larger amount of detail than do1H and13C NMR spectroscopy. Symmetric and asymmetric dimethylol urea can be clearly distinguished and separated from monomethylol urea, trimethylol urea, and methylene-bridged urea. The existence of hemiformals of methylol urea is confirmed. 1,3,5-Oxadiazinan-4-on (uron) and its derivatives were not found in the reaction mixtures investigated here but were prepared via alternative routes. The molar ratios of formaldehyde to urea were 1, 2, and 4, the pH values 7.5 and 8.5, and the reaction temperature 60 °C. Copyright 2014 John Wiley & Sons, Ltd. 15N-enriched urea is used in combination with quantitative15N and13C NMR spectroscopy and a Virtual Reference. This allows for a detailed peak assignment and absolute quantification of the early steps of this industrial process, which involves a complex reaction network. A detailed peak assignment for all three nuclei, a full quantitative description of the reaction mixture's composition and a model describing changes in shift depending on formaldehyde substitution are given. Copyright
Canonical Chemical Theories Exemplified by the Mehtylolation of Urea and Melamine
Gebregiorgis, Taddesse,Gordon, Manfred
, p. 359 - 382 (2007/10/02)
Old and recent data on equilibria and kinetics of methylolation of urea and melamine are analysed.The theoretical framework affords a sequence, claimed to be canonical of successive phenomenological approximations.The theory, expounded earlier, begin with two successive schemes whose essentials go back to early work by Pauling and by Flory.The two stages here suffice to show that all the data from eight laboratories, covering the six-membered family of methylol ureas and rhe ten-membered family of methylol melamines, are in quantitative agreement, a circumstance unsespected by other workers in the field.The statisticalthermodynamic and kinetic principles involved are therefore expounded in more detail than before.Using them, very small substituent effects (e.g O.35 kJ kol-1 are deduced with high significance and accuracy.Owing largly to the recent measurement by Tomita, the methylol melamines are claimed currently to be the thermdinamically best characterised family in the chemical literature.A challenge arises for theoretical chemists to test quantum-theoreticaltechniques against the measured energetics of substituent effects in this family, and to exploit for other families the graph-theoretical analysis of molecular additivity which underlies the approximation schemes, which already well tested.
