Intermolecular hydrogen bonding. I. Effects on the physical properties of tetramethylurea-water mixtures

Abstract

3313phate diester anions. The comparisons between our experimental results and the results of both sets of calculations are not as direct as we should like.The theoretical calculations of Collin and of Boyd were carried out with model compounds which are not the same as any in our series but several in each set bear a strong resemblance to ones in our present set. We conclude from our experimental results that Boyd's set of calculations6 is more valid than the other with the regard to the net charge on the phosphoryl oxygen.We are more satisfied that our previous explanation* of the inversion of the values of KL for the methyl-and ethylpiperidinium cations in the case of the oxygen-containing ligands is a correct one in view of the excellent correlation of the values of the ratios KL(Et)/KL(Me) and VPO. Vapor pressures, viscosities, densities, surface tensions, heat of mixing, and molar refractivities of watertetramethylurea mixtures were measured at temperatures from 25 to 85'. The data show that the tri-to pentahydrates are the most stable water-tetramethylurea species formed.

Effect of temperature and ionic strength on volumetric and acoustic properties of solutions of urea alkyl derivatives in aqueous NaCl

“…As it can be seen, our data for density are in good agreement with those found in the literature [15,16,[20][21][22][23][24][25][26][27] a specially with those reported by Ivanov at al [15]. The comparison of the acoustic data is rather impossible due to the lack of such data in the literature.…”

Thermal Expansion and Structure of 1,3-Dimethylurea, Tetramethylurea, and Tetrabutylammonium Bromide Aqueous Solutions Derived from Density Measurements

“…With TMU solution m(V j 2,min ) ) ≈ 1.7 mol • kg -1 , above that composition one expects stronger interaction (overlapping) of the hydrated species. Nevertheless, the interaction here results in a unique behavior of the solution, which is reflected besides the anomalous V j 1,E E isotherms; by a maximum of the heat of mixing at ∼ 4 molality, 28 by the unique behavior of positron annihilation 10 and also by an azeotropic vapor pressure maxima over the (∼2 to 4) molality range. 7 A slight vapor pressure maxima appears already at ∼ 320 K and increases up to 50 % above the Raoult's law value at 283 K. From the strong nonideality of the solution, one can conclude that below 283 K the hydration interaction results in microheterogenity, and the solution structure is very close to phase separation with an "upper critical solution temperature", UCST.…”

Anharmonic coupling between fundamental modes in tetramethylurea

“…1,2 Experimental and theoretical studies about pure liquid TMU and binary mixtures of TMU with other solvents have been reported. [3][4][5][6][7][8][9] Due to the presence of the oxygen site and four methyl groups, the TMU molecule can be considered a suitable solute for probing hydrophobic as well as hydrophilic interactions.…”