Density of lithium fluoride—lithium carbonate-based molten salts

The density of the LiF-Li₂CO₃ melts system was measured using the Archimedean method. Using the quadratic regression orthogonal design with two factors, a regression equation for the density of LiF-Li₂CO₃ melts was obtained in which the concentration of LiF and temperature were considered. The results indicated that the density of the LiF-Li₂CO₃ melts decreased with either increasing the concentration of LiF or increasing temperature; a linear relation was observed between density and temperature. In addition, the influences of NaF, KF, NaCl, and KCl additives on the densities of the given systems were studied. The addition of NaF and KF increased the density of the melts, whereas NaCl and KCl resulted in an initial increase and subsequent decrease with an increasing additive concentration. The density attained a maximum at NaCl and KCl mass fraction of approximately 15%.     

Efficient method for the synthesis of polysubstituted 2,6-dicyanoanilines by one-pot three-component tandem reaction of malononitrile with <Emphasis Type="Italic">α</Emphasis>,<Emphasis Type="Italic">β</Emphasis>-unsaturated imines

A facile and efficient one-pot synthesis of polysubstituted benzenes was achieved via the Michael addition of malononitrile with α,β-unsaturated imines and a sequential tandem reaction. This reaction generates polysubstituted 2,6-dicyanoanilines in high yields (15 examples, isolated yields of 57–91 %), and proceeds under mild reaction conditions (60°C, 10 min). In addition, a possible mechanism accounting for the reaction is proposed.     

Exact solutions to magnetogasdynamic equations in Lagrangian coordinates

The Lie group of point transformations, which leave the equations for a simplified model of one dimensional ideal gas in magnetogasdynamics invariant, are used to obtain some exact solutions for the governing system of hyperbolic partial differential equations (PDEs). Similarity variables which reduces the governing system of PDEs into system of ordinary differential equations (ODEs) are determined through the transformations. The resulting ODEs are solved analytically to obtain some exact solutions that exhibits space-time dependence. Further, we study the propagation of weak discontinuity through a state characterized by one of the solutions.     

The significance of a second adsorption phase with weakly adsorbed species for the calculation of the surface concentrations of a mixture: methanol–DME and methanol–ethene adsorption in SAPO-34

With the calorimetric (adsorption heat versus coverage) curve also measured together with the adsorption isotherm, the simultaneous use of both curves showed that there were two phases of adsorption in the adsorption of methanol, dimethyl ether, ethene and propane in SAPO-34. The dual-site Langmuir equation gave good fits to the adsorption data to support the interpretation that a second (type 2) adsorption phase occurred in the high-pressure region in addition to a first (type 1) adsorption phase on the acid sites at lower pressures. Adsorption experiments and calculations using binary gas mixtures showed that due to the existence of two types of adsorption, the multicomponent Langmuir isotherm equation (Langmuir competitive adsorption model) calculated incorrect surface concentrations when the concentrations were high. In contrast, the ideal adsorbed solution theory (IAST) calculated correct surface concentrations in the adsorption of mixtures.     

Comparative theoretical study on the corrosion inhibition properties of benzoxazole and benzothiazole

Research on Chemical Intermediates - The electronic parameters of two azole molecules, namely benzoxazole (BOX) and benzothiazole (BTH), have been studied using DFT/B3LYP, MP2, and HF methods with...     

A Single Enzyme Transforms a Carboxylic Acid into a Nitrile through an Amide Intermediate

The biosynthesis of nitriles is known to occur through specialized pathways involving multiple enzymes; however, in bacterial and archeal biosynthesis of 7‐deazapurines, a single enzyme, ToyM, catalyzes the conversion of the carboxylic acid containing 7‐carboxy‐7‐deazaguanine (CDG) into its corresponding nitrile, 7‐cyano‐7‐deazaguanine (preQ₀). The mechanism of this unusual direct transformation was shown to proceed via the adenylation of CDG, which activates it to form the newly discovered amide intermediate 7‐amido‐7‐deazaguanine (ADG). This is subsequently dehydrated to form the nitrile in a process that consumes a second equivalent of ATP. The authentic amide intermediate is shown to be chemically and kinetically competent. The ability of ToyM to activate two different substrates, an acid and an amide, accounts for this unprecedented one‐enzyme catalysis of nitrile synthesis, and the differential rates of these two half reactions suggest that this catalytic ability is derived from an amide synthetase that gained a new function.