Structural studies of cyclic ureas: 2. Enthalpy of formation of parabanic acid

Experimental and computational study of the energetics of hydantoin and 2-thiohydantoin

“…Results of a typical experiment for each compound are presented in table 2; Dm(H 2 O) is the deviation of the mass of water added to the calorimeter from 2900.0 g or 5222.5 g, depending of the calorimeter used; DU R is the energy correction to the standard state; DU(IBP) is the internal energy for the isothermal bomb process calculated according to equation (8). The remaining terms have been previously described [34,35].…”

“…Experimental and computational studies for compounds with pentagonal ring cores, with two nitrogen atoms or a nitrogen and an oxygen or sulfur as heteroatoms, in the positions 1,3-, has been studied recently [5][6][7][8]. Other studies on the energetic of five-membered nitrogen heterocycles fused to a benzenic ring [9][10][11] have been also described in the recent literature.…”

Structural studies of cyclic ureas: 3. Enthalpy of formation of barbital

“…However and surprisingly, the average value of both calculations is À635.0 kJ Á mol À1 . Work is in progress to understand these anomalies since in previous works, particularly G3 calculated values were very close to experimental ones, for instance in parabanic acid [8], where the experimental and G3 calculated values are À{(470.8 ± 1.2) and À469.5} kJ Á mol À1 , respectively. …”

“…This paper is the third on a series of papers concerned with the structural studies of cyclic ureas in which were presented the thermophysical and thermochemical studies of imidazolidine-2-one (1) and N,N 0 -trimethyleneurea (3) in the first paper [7] and of parabanic acid (2) in the second one [8]. As we have referred in the previous papers, the main purpose of these studies is to provide reliable data for this class of compounds that can be used both for the estimation of the thermochemical properties of related compounds that are not easy to study experimentally and also to understand the influence of steric, electrostatic, and stereo-electronic interactions produced by substituents on the thermochemical stability of these molecules.…”

Energetic studies of urea derivatives: Standard molar enthalpy of formation of 3,4,4′-trichlorocarbanilide

“…Besides its bacteriostatic properties, only the melting point was reported as T = (528.4 to 529.2) K. We decided to study the thermochemical properties and the crystal structure of TCC to finish a series of papers devoted to ureas: imidazolidin-2-one and N,N 0 -trimethyleneurea [2], where the structure of the related benzimidazolinone was also discussed, parabanic acid [3], and finally barbital [4].…”