RESUMO
A new approach for the classification of solvents is proposed, based solely on the solvent molecular structure and relying on the "COnductor-like Screening MOdel for Real Solvents" (COSMO-RS), in which solvents are considered in their liquid state. This approach provides an a priori classification without requiring the knowledge of any experimental data. The theoretical descriptors of the proposed classification are generated through the analysis of the COSMO-RS σ-potential profiles. By applying a two-step statistical procedure to the descriptors generated for a set of 153 representative solvents, a clustering into 10 classes leads to an optimal classification that is compared to the classical Chastrette's classification. The investigation of nitrocellulose solubility allows a validation of the proposed classification, which can be extended also to solvent mixtures. This new approach for solvent classification, thus, appears as a consistent tool for the design of new solvents and their formulation.
RESUMO
The fish-tail temperatures denoted as T* have been determined or collected for 85 ternary systems based on three tetraethylene glycol monoalkyl ethers C(i)E(4) (i = 6, 8, 10), water, and 43 hydrocarbon oils of various hydrophobicities. Fourteen fragrant mono- and sesquiterpenes in addition to 29 model oils, including n-alkanes, cyclohexenes, cyclohexanes, and alkylbenzenes, were investigated in order to establish a QSPR model for the prediction of T* as a function of the chemical structure of the oils. Only two molecular descriptors related to branching and molecular size (Kier A3) and polarizability (average negative softness) of the molecules are necessary to model and predict the values of T* and EACN (equivalent alkane carbon number) of unsaturated and/or cyclic and/or branched hydrocarbons exhibiting an EACN ranging from -4 and +35. Results are discussed in terms of evolution of the effective packing parameter of the surfactants according to temperature and oil penetration into the interfacial film.
RESUMO
The hydrotropic properties of short-chain monoalkyl ethers of isosorbide have been studied with emphasis on the difference between the two regioisomers (2-O- and 5-O-monoalkylisosorbide, C(i)Iso-exo and C(i)Iso-endo, respectively). On the one hand, the partitioning in a water/cyclohexane system has been measured, and on the other hand, the "optimal formulation" of C(i)Iso/oil/water systems has been determined by changing the oil polarity. In both cases, whatever the alkyl chain length (four or five carbons), C(i)Iso-exo appears to be less hydrophilic due to an intramolecular hydrogen bond that makes the free hydroxyl group less available. With one substituted position, the hydrophilicity contribution of isosorbide is slightly higher than the one of two ethylene glycols when the exo hydroxyl remains free, whereas it is closer to one ethylene glycol when this hydroxyl is substituted. With regard to the sensitivity to temperature, the hydrophilicity loss on heating seems to be similar for both isomers and close to what is obtained for poly(ethylene glycol) derivatives if we consider the evolution of the partition coefficients. In C(i)Iso-endo/oil/water systems, however, the variation of the optimal oil with temperature tends to show that the isosorbide derivatives are approximately 2 times less sensitive than their poly(ethylene glycol) counterparts to temperature changes.
RESUMO
In this paper, we study the thermodynamic and structural changes of crystalline linaprazan (a proton pump inhibitor) upon high-energy ball milling at room temperature. The investigations have been performed by differential scanning calorimetry and powder X-ray diffraction. The results indicate that this drug undergoes a direct crystal-to-glass transformation upon milling. Moreover, upon heating, the amorphous material obtained by milling is shown to recrystallize toward two different polymorphs that appear to form a monotropic set.