On June 19, 2020, Sandler, Isolde; Larik, Fayaz Ali; Mallo, Neil; Beves, Jonathon E.; Ho, Junming published an article.Quality Control of 1,3-Diphenylurea The title of the article was Anion Binding Affinity: Acidity versus Conformational Effects. And the article contained the following:
High-level quantum chem. calculations were used to elucidate the gas- and solution-phase conformational equilibrium for a series of sym. substituted (thio)ureas, (thio)squaramides, and croconamides. Gas-phase calculations predict that the thermodn. conformer of many of these anion receptors is not the dual-hydrogen-bond-facilitating anti-anti conformer as is commonly assumed. For N,N’-diaryl thiosquaramides and croconamides, the syn-syn conformer is typically the predominant conformer. Solution-phase calculations show that the anti-anti conformer is increasingly stabilized as the polarity of the solvent increases. However, the syn-syn conformer remains the lowest energy conformation for croconamides. These predictions are used to explain the acidity vs. chloride binding affinity correlations recently reported for some of these compounds The chloride binding constants for thioureas and croconamides are significantly lower than expected on the basis of their pKa values, and this may be due in part to the need for these receptors to reorganize into the anti-anti conformer. Exptl. NMR nuclear Overhauser effect (NOE) measurements of an asym. substituted squaramide and its thio analog are consistent with the syn-syn conformation being predominant at 298 K. The conformational equilibrium should therefore be an important consideration for the design and development of future anion receptors and organocatalysts. The experimental process involved the reaction of 1,3-Diphenylurea(cas: 102-07-8).Quality Control of 1,3-Diphenylurea
The Article related to urea thiourea squaramide thiosquaramide croconamide, receptor anion binding affinity acidity conformational effect, Physical Organic Chemistry: Other Reactions, Processes, and Spectra and other aspects.Quality Control of 1,3-Diphenylurea
Referemce:
Amide – Wikipedia,
Amide – an overview | ScienceDirect Topics