Generalized Prediction of Enthalpies of Formation Using DLPNO-CCSD(T) Ab Initio Calculations for Molecules Containing the Elements H,C, N,O, F,S, Cl,Br

The prediction of thermochemical properties such as enthalpies of formation is of crucial importance, both in research and industrial applications, especially for systems involving not well-characterized molecules, such as biomass systems (bio-oils), or systems involving new compounds (new-generation refrigerants). It is highly desirable to obtain an efficient method by which these values can be predicted. Ab initio-based calculations can be very accurate for predicting gas phase thermochemical properties and are usually more versatile than group contribution methods. In this work, we propose a general extension of the work of Paulechka and Kazakov, using very accurate and efficient domain-based local pair natural orbital-coupled cluster theory ab initio calculations, to determine the enthalpies of formation of a broad variety of molecules. New sets of regressed atomic contributions are proposed for a larger group of elements: H, C, N, O, F, S, Cl, and Br. Excellent predictions are obtained for the most studied compounds (bio-oil compounds and refrigerants). © 2019 Wiley Periodicals, Inc.     

Removal of dithioterethiol (DTT) from water by membranes of cellulose acetate (AC) and AC doped ZnO and TiO2 nanoparticles

Dithioterethiol (DTT) is a typical example of substances that contain sulfur with adverse effects on human health. Membranes-based cellulose acetate is used for the separation processes of thiols after the addition of ZnO and TiO₂ nanoparticles. The measurement of permeability allows us to estimate the efficiency of membrane cleaning. The permeability increases from 8.82 L.h^?1.m^?2.bar^?1 for CA membrane to 20.77 L.h^?1.m^?2.bar^?1 for CA-TiO₂ and 21.96 L.h^?1.m^?2.bar^?1 for CA-ZnO membranes. For the permeability values of DTT, we noted that the CA-ZnO membrane has the highest permeability (50.66 L.h^?1.m^?2.bar^?1). The CA-ZnO membrane changes from nanofiltration to ultrafiltration membrane. On the other hand, for the CA-TiO₂ modified membrane, the permeability decreases to 6.00 L.h^?1.m^?2.bar^?1. The CA-TiO₂ membrane is in the category of reverse osmosis membranes. This variation is explained by the interaction between nanoparticles and DTT. The contact angles of the incorporated membranes decrease progressively with the addition of TiO₂ or ZnO-NPs. The low contact angle with water means high hydrophilicity, indicated that the addition of TiO₂ and ZnO improved the hydrophilicity of the membranes. The CA membrane had the highest contact angle with water of 92.64 ± 1.5°. After the addition of 0.1 g of TiO₂ or ZnO, the contact angle of CA-TiO₂ and CA-ZnO was reduced to 86.7 ± 0.2° and 70.51 ± 1.5°, respectively. Both TiO₂ and ZnO caused strong hydrophilicity of membranes. From the elimination rates of DTT, it is concluded that there are optimal conditions of (1) Pressure P = 2 bars, (2) pH = 10 and (3) DTT concentration = 2 mM.     

N-Bromosuccinimide-dimercaptoethane cobromination of alkenes: synthesis of β,β′-dibromodithioethers

Alkenes react in diethyl ether with N-bromosuccinimide (NBS) and dimercaptoethane to afford the corresponding β,β′-dibromodithioethers. Bromine and dimercaptoethane are added to the aliphatic terminal olefins in an anti-Markovnikov fashion.     

Solution Thermodynamics of Piroxicam in some Ethanol + Water Mixtures and Correlation with the Jouyban–Acree Model

The solubility of piroxicam (PIR) in several ethanol + water mixtures was determined at five temperatures from 293.15 to 313.15 K. The thermodynamic functions; Gibbs energy, enthalpy, and entropy of solution and of mixing were obtained from these solubility data and the drug properties of fusion by using the van’t Hoff and Gibbs equations. The greatest solubility value was obtained in pure ethanol. A non-linear enthalpy–entropy relationship was observed from a plot of enthalpy versus Gibbs energy of solution. Accordingly, the driving mechanism for PIR solubility in water-rich mixtures is the entropy, probably due to water-structure loss around the drug’s non-polar moieties by ethanol, whereas, in ethanol-rich mixtures the driving mechanism is the enthalpy, probably due to better PIR solvation by the co-solvent molecules. The solubilities and the derived thermodynamic properties in mixed solvents were correlated using the Jouyban–Acree model.