Heat capacities of ureas and water in water and dimethylformamide

Apparent molar volumes and apparent molar heat capacities of aqueous urea, 1,1-dimethylurea, and N,N′-dimethylurea at temperatures from (278.15 to 348.15)K and at the pressure 0.35MPa

“…No attempt will be made here to label these compounds as either ''structure makers'' or ''structure breakers'' based on their V / (T, m) behavior. All that seems clear is that these three urea compounds show different V / vs. m relationships: V / is positively correlated with m for aqueous [13]; h, reference [12]; j, reference [14]; m, reference [20]; ,, reference [4]; n, reference [21]. FIGURE 5.…”

“…We used the reciprocals of the squares of the uncertainties reported in tables 5 to 7 as weighting factors in the regressions, and values of the resulting c i are given in table 8. The regression surfaces for equation (3), our experimental C p,/ values from tables 5 to 7, and the literature C p,/ values [4,[12][13][14]20,21] for the three aqueous urea compounds are shown in figures 4 to 6. The differences between our regression surfaces and values of C p,/ from the literature are as follows: for urea, average difference D = +0.3 J AE K À1 AE mol À1 , range of differences D = À12.7 J AE K À1 AE mol À1 [13] to D = +5.9 J AE K À1 AE mol À1 [13]; for 1,1-dimethylurea, average difference D = +1.6 J AE K À1 AE mol À1 , range of differences D = +6.0 J AE K À1 AE mol À1 [4] to D = À3.3 J AE K À1 AE mol À1 [4]; and for N,N 0 -dimethylurea, average difference D = +6.3 J AE K À1 AE mol À1 , range of differences D = +11.3 J AE K À1 AE mol À1 [4] to D = +1.9 J AE K À1 AE mol À1 [4].…”

“…using parameters in column 3 of table 8. s, experimental values from table 6; ,, reference[4]; n, reference[21].…”

Prediction of the glass transition in aqueous solutions of simple amides by molecular dynamics simulations

“…water-acetamide interactions are stronger than water-water interactions, the hydrophobic hydration of the methyl group of acetamide is the dominant feature, as it enhances the overall structure of water [35,38].…”

Influence of electrolytes/non-electrolytes on the cloud point phenomenon of the aqueous promethazine hydrochloride drug solution

“…Two different mechanisms have been proposed to explain the effect of urea on micellar systems [28,29]: (i) urea affects only the solvent changing the water-structure and promoting the dissolution of the hydrophobic species [30] (indirect mechanism), and (ii) urea participates in the solvation of the hydrophobic species by replacing some water molecules in the hydration shell of the solute (direct mechanism). The first mechanism is the most widely accepted one and urea is considered as water-structure breaker [31,32]. However, Monte Carlo and molecular dynamics calculations suggest that there are very small differences between the properties of bulk and interfacial water [33,34], hence, favoring the direct mechanism.…”