Modified Natural Dolomite and Its Influence on the Production of Glycerol Carbonate: Effects of Structural and Basicity Properties.

A systematic study over different treatment conditions, including hydrothermal and acid-thermal, was successfully carried out to determine the most suitable conditions to enhance the textural properties and surface chemical composition of natural dolomite. The reconstruction of dolomite after various treatments enhanced the surface area by 4-5 times and diminished the pore diameter between 70% and 81% compared to the untreated parent dolomite. The Rietveld analysis of the X-ray diffraction (XRD) patterns revealed changes in the crystalline compositions after each treatment. When the treated dolomite was used as a catalyst to produce glycerol carbonate via a transesterification reaction of glycerol and dimethyl carbonate, the crystalline Ca(OH)2 concentration of the modified dolomite and the apparent glycerol carbonate formation rate (rgc) are well-correlated. The results suggest that an increase of the crystalline Ca(OH)2 concentration could be related with surface basicity at the weak and moderate strength sites that may lead to an increase in catalytic activity. The hydrothermal treated dolomite showed a selectivity of glycerol carbonate greater than 99% and rgc value 3.42 mmol/min·gcat, which was higher than that achieved on other samples. This study could aid to the proper selection of dolomite treatment for the desired crystalline composition, depending on the applications of this highly available mineral.

The Acid/Base Characterization of Molecules with Epigenetic Activity.

The acidic and basic functional groups in a molecule strongly influence its physicochemical properties, affinity for a macromolecule, pharmacokinetics, and toxicity. For instance, basicity has been correlated with molecular promiscuity, hERG blockade, and phospholipidosis. Nonetheless, no systematic characterization of the acid/base profile of epigenomic databases has been reported. This study describes an analysis of the acidic ionization constant distribution of a library of 7820 compounds with reported activity against epigenetic targets. Furthermore, the epigenomics database's acid/base profile was compared to the reference libraries of food chemicals, natural products, and approved drugs. It was found that the acid/base profile of histone lysine demethylase ligands is more similar to previously approved drugs, and histone acetyltransferase ligands have acidic and basic functional groups largely found in food chemicals and natural products; this support the potential of these libraries for finding new epigenetic inhibitors.

Analysis of the Acid/Base Profile of Natural Products from Different Sources.

For many years drug discovery and other areas in chemistry have successfully relied on natural products. Recent advances in computational methods have made possible to study the chemical space of natural products from different sources. Ionizable acidic and basic functional groups heavily influence physicochemical properties and thus a molecule's absorption, distribution, metabolism, excretion, and toxicity characteristics as well as their affinity for biological targets. This work reports the generation and critical comparison of the acid/base profiles of ten chemical databases including seven natural products sets from different origins, a set of semisynthetic compounds, a collection of approved drugs, and a compendium of food chemicals. Similarities were found in the proportion of the main charge state categories among the natural products databases with few differences in their pKa distributions. Clear differences were observed between natural products and the approved drugs and semi-synthetic natural products databases, whereas natural products share some trends with the food chemical database. We noted that the natural products collections comprise around 45 % of neutral compounds. The proportion of single acids was approximately twice that found for FDA drugs, and they demonstrated a similar distribution of pKa values. In contrast to drugs, only 5 % of compounds among the natural products sets had a single basic group. Likewise, simple ampholytes were less prevalent in the natural products databases relative to drugs.

The Acid/Base Profile of a Large Food Chemical Database.

Molecular acid/base properties have a significant influence on membrane permeation, metabolism, absorption, and affinity for biological targets. In particular, ionizable groups are critical in the strength of target-molecule interactions, pharmacokinetics, and toxicity. In this study, we estimated the acid/base properties of the food chemicals from FooDB, a public compound collection with more than 22,000 compounds. It was found that the food chemicals have 40.9 % of neutral compounds, which is twice as many as that found in approved drugs. The most common functional groups among the acid groups in the food chemicals were phenols (16.1 %), phosphates (17.3 %), and carboxylates (17.3 %) while the single-base-containing compounds were of less interest as they accounted for just 5.5 %. To the best of our knowledge, this is the first systematic acid/base profiling of food chemicals and it is part of a continued effort to profile food chemicals for their broad interest in several areas such as nutrition and the food industry in general.

Gutmann's Donor Numbers Correctly Assess the Effect of the Solvent on the Kinetics of SN Ar Reactions in Ionic Liquids.

We report an experimental study on the effect of solvents on the model SN Ar reaction between 1-chloro-2,4-dinitrobenzene and morpholine in a series of pure ionic liquids (IL). A significant catalytic effect is observed with reference to the same reaction run in water, acetonitrile, and other conventional solvents. The series of IL considered include the anions, NTf2 (-) , DCN(-) , SCN(-) , CF3 SO3 (-) , PF6 (-) , and FAP(-) with the series of cations 1-butyl-3-methyl-imidazolium ([BMIM](+) ), 1-ethyl-3-methyl-imidazolium ([EMIM](+) ), 1-butyl-2,3-dimethyl-imidazolium ([BM2 IM](+) ), and 1-butyl-1-methyl-pyrrolidinium ([BMPyr](+) ). The observed solvent effects can be attributed to an "anion effect". The anion effect appears related to the anion size (polarizability) and their hydrogen-bonding (HB) abilities to the substrate. These results have been confirmed by performing a comparison of the rate constants with Gutmann's donicity numbers (DNs). The good correlation between rate constants and DN emphasizes the major role of charge transfer from the anion to the substrate.

Influencia de l química superficial en la entapía de inmersión de carbones acctivados en soluciones acuosas de fenol y 4-nitro fenol / The influece of superficil chemistry in the immersion enthalpy of activaated carbon in aqueous solutions of phenol and 4-nitrphhenol

Se estudian las interacciones de cinco muestras de carbón activado obtenidas a partir de diferentes materiales lignocelulósicos, con diferente grado de activación alrededor de 20%, con soluciones acuosas de fenol y 4-nitro fenol mediante la determinación de las entalpías de inmersión. Se establece que los carbones activados obtenidos son de carácter básico y presentan valores para el punto de carga cero (PZC), que varían entre 7,4 y 9,7, y contenidos de basicidad total mayores en todos los casos que los valores obtenidos para la acidez total. Se determina la entalpía de inmersión de los carbones activados en soluciones de NaOH y HCl con valores mayores para la entalpía de inmersión en HCl que se encuentran entre 32,6 y 68,3 Jg-1. Las entalpías de inmersión en solución de fenol se hallan entre 7,6 y 13,9 Jg-1, y para el caso del 4-nitro fenol se encuentran entre 12,7 y 20,5 Jg-1; con valores mayores para todas las muestras para la inmersión en el segundo compuesto.

The interactions between five samples of activated carbon with different activation grades (~20%, obtained from different lignocellulose’ s materials) and aqueous solutions of phenol and 4-nitrofenol were studied by determining the values of the immersion enthalpy. From this study, it is established that the activated carbons exhibit a basic character and show values for the point of zero charge (PZC) between 7.4 and 9.7; also, the total basicity content is greater in all cases than the value obtained for the total acidity. The immersion enthalpy values of the activated carbons in NaOH and HCl solutions were determined, yielding larger values in the case of HCl which are between 32.6 -68.3 Jg-1. The inmersion enthalpy values in phenol solution range between 7.6 y 13.9 Jg-1 and for 4-nitro fenol between 12.7 y 20.5 Jg-1; all the samples displayed greater values after immersion in the second compound.