Dielectric constants, viscosities, densities, and refractive indices of three urea derivatives were measured at various temperatures ranging from 25 to 100 °C. The experimental data as functions of temperature were fitted precisely to appropriate equations. Dielectric constant data indicated a significant increase in dielectric constant of the cyclic ureas over that of the acyclic homologs. Kirkwood correlation factors and the activation energies of viscous flow were also evaluated. Values for Kirkwood correlation factors ranged from 1.07 to 1.21. This range indicates but does not substantiate parallel dipole association. Activation energies ranged from 3.3 to 4.4 kcal/mol.

N-Alkylated ureas, including cyclic derivatives. are readily obtained pure. These stable compounds are already used as industrial solvents owing to their considerable solvent power, their wide liquid range, and their favorable dielectric constants and dipole moments. They are being increasingly employed as reaction media for electrochemical and analytical studies.

JOSEPH ROSENFARB and JOSEPH A . CARUSO. Can. J. Chem. 54, 3492 (1976). A series of lithium, sotlium. potassium, and ammonium salts were investigated by proton magnetic resonance spectroscopy in 1,3-di1nethyIethylene~~rea. a relatively new non-aqueous solvent of high polarity and moderately high dielectric constant. The salts were found to shift the solvent proton peaks linearly as a function of salt concentration. Thiosulfate, perchlorate, and iodide salts shifted the solvent peaks downfield while tetraphenylborate salts uniquely shifted the peaks upfield indicating an ~~n u s u a l type of solvation behavior for the tetraphenyiborates in this solvent.JOSEPH ROSENFARB et JOSEPH A. CARUSO. Can. J. Chem. 54, 3192 (1976). On a CtudiC par rmil du proton dans la dimCt11y-1-1.3 ethylkne urke un solvant non aqueux relativement nouveau de haute polarit6 et de constante dieiectrique modCree, une sCrie de sels de lithium, de sodium, de potassium et d'ammonium. On a trouve que les sels dkplacent les signaux des protons du solvant d'une f a~o n lineaire en fonction de la concentration du sel. Les sels du thiosulfate. du perchlorate et de l'iodure deplacent les pics du solvant vers les bas champs alors que les sels du tCtraphinylborate sont les seuk B tiiplacer les pics vers les hauts champs; ces resultats indiquent un type particulier de colnportemene desolvatation des iCtraphenylborates dans ce solvant.[Traduit par le journal]Proton magnetic resonance which has been used to investigate the solvation behavior of ions in aqueous solutions (1-4) has bcen extended t o non-aqueous media as well (5). Recently 1,3-dimethylethyleneiirea (DMEU) has been investigated with regard t o somc of its fundamental properties (0) and to the behavior of electrolytes therein (7,8). It was found that DMEU is a solvent of high polarity (4.09 in dioxane) (9), moderately high dielectric constant (37.6 at 1 MHz) (6). and possesses good dissociative power towards electrolytes, comparable to that of hr-methyl-2-pyrrolidone and methanol. Particularl!~ interesting kvas the property that sodium and potassiu:~~ salts were isoconducting in DMEU (7). Therefore further study into the nature of solvation in DMEU was indicated.cipitates were thoroughly washed with deionized water, dried, and recrystallized from acetone with water portions. All salts were finely ground and dried in the appropriate manner (5, 7, 10).DMEU was freshly prepared as previously described (6) and had a specific conductance of about 5 X ohm-' ~111-1. MeasurenzetztsChemical shift data were obtained using a Varian A-60 nmr spectrometer. Tetramethylsilane ( 5 ' ; ) was used as an internal reference from which peak shifts were calculated. Since an internal reference was used. no bulk diamagnetic correctio~s were applied (11). Shift data were reproducible to t 0.3 Hz or 0.005 ppm.Results and Discussion A number of alkali halides, tetraalkylammonium salts, and multivalent salts have been investigated in aqueous solution (1,12). It was Experimentalobserved that a downfield (negative) shift of...

N-Alkylierte Harnstoffe, auch cyclische Derivate, sind gut in reiner Form zu erhalten. Diese stabilen Verbindungen werden aufgrund ihres hohen Losungsvermogens, ihres grofien Flussigkeitsbereichs sowie der giinstigen Dielektrizitatskonstanten und Dipolmomente bereits als Losungsmittel fur technische Zwecke genutzt. Eine breitere Anwendung als Reaktionsmedien fur elektrochemische und analytische Untersuchungen zeichnet sich ab.

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