Catalytic application of a nano-molten salt catalyst in the synthesis of biological naphthoquinone-based compounds

Research on Chemical Intermediates - In this investigation, a new application of 1H-imidazol-3-ium tricyanomethanide catalyst was explored. The catalyst presented a robust catalytic applicability...     

An Objective Alternative to IUPAC's Approach To Assign Oxidation States

The IUPAC has recently clarified the term oxidation state (OS), and provided algorithms for its determination based on the ionic approximation (IA) of the bonds supported by atomic electronegativities (EN). Unfortunately, there are a number of exceptions and ambiguities in IUPAC's algorithms when it comes to practical applications. Our comprehensive study reveals the critical role of the chemical environment on establishing the OS, which cannot always be properly predicted using fix atomic EN values. By identifying what we define here as subsystems of enhanced stability within the molecular system, the OS can be safely assigned in many cases without invoking exceptions. New insights about the effect of local aromaticity upon OS are revealed. Moreover, we prove that there are intrinsic limitations of the IA that cannot be overcome. In this context, the effective oxidation state (EOS) analysis arises as a robust and general scheme to derive an OS without any external guidance.     

Selection of excipients for the development of carvedilol loaded lipid-based drug delivery systems

Journal of Thermal Analysis and Calorimetry - Carvedilol (CARV) is a widely used drug, which has shown low oral bioavailability. Lipid-based drug delivery systems (LBDDS) appear as promising...     

Colorimetric characteristics of the phenolic fractions obtained from Tempranillo and Graciano wines through the use of different instrumental techniques

The aim of the present work was to determine whether there is any relationship between measurement by transmission and reflection (in the latter case, with and without contact with the sample). We also evaluated which methodology used would offer a better interpretation of the results in visual terms. For this purpose, different colorimetric techniques such as transmission spectrophotometry, diffuse reflectance spectrophotometry and spectroradiometry were applied. The samples consisted of increasing dilutions (0, 20, 40, 60, 80 and 100%) of the phenolic fractions obtained from 4 wines: Tempranillo (T) and Graciano (G) monovarietal wines, and two 80:20 mixtures: M (wine elaborated by blending grapes) and W (a blend of the T and G wines) (9 fractions per wine). Fractionation was performed using gel permeation chromatography with a Toyopearl HW-40S column, and the dilutions of the fractions were performed with synthetic wine (pH = 3.6). The spectroradiometric measurements permitted the differences due to the dilution effect on the fractions to be established more clearly than with the results obtained using diffuse reflectance and spectrophotometry. Thus, this technology is very suitable for use in comparative interpretations by the human eye. In turn, we assessed the changes in colour due to the effect of dilution on the fractions, observing that the effect of dilution led to an increase in the values of lightness (L*), while the chroma values (C*_ab) followed the opposite trend, in agreement with its role as a variable related to chromatic intensity or vividness of the sample. In contrast, hue (h_ab) did not seem to be affected by dilution of the fractions, in consonance with the qualitative nature of this parameter.     

Adsorption properties of silica-based sorbents containing phosphonic acid residues

Isotherms are measured for nitrogen, n-hexane, triethylamine, and water vapor adsorption on silicas of different origins, the surface layers of which contain functional groups of the ??Si(CH₂)₂P(O)(OH)₂ composition, namely, ethylene- and phenylene-bridged polysilsesquioxane xerogels produced by the sol-gel method, silica microspheres synthesized from tetraethoxysilane in the presence of [CH₃(CH₂)₁₇N(CH₃)₃]Br as a template by spray-drying method, and SBA-15 mesoporous silica produced based on tetraethoxysilane using Pluronic 123 as a template. It is shown that all of the samples possess high specific surface areas, while the types of adsorption isotherms and the accessibility of active acidic sites for adsorption interactions with electron-donor molecules depend on the structures of pores and surface layers, which are governed by the methods of synthesis and postsynthesis sample treatment.