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The choice of solvent plays a crucial role in aldol reactions, often affecting both the conversion rate and stereoselectivity. In this study, we investigated the influence of solvents (water, methanol and hydroalcoholic) on the proline-catalyzed aldol reactions. We focused on elucidating the solute–solvent interactions at the rate-determining step and the stereoselective step. Our theoretical finding suggests, hydroalcoholic-mediated reaction exhibits a higher conversion rate as compared to pure water and pure methanol-mediated system with the generation of most stable transition state structure. This can be attributed to the existence of strong hydrogen bonding and the formation of stable six-membered transition state structures in hydroalcoholic-mediated system. In addition to this, our research demonstrates that the choice of solvent plays a crucial role in determining the percentage of enantiomeric excess in the reaction. Theoretical finding suggest that the anti-product is preferentially formed in the presence of water and hydroalcoholic media as solvents. Pure water and hydroalcoholic solvents surprisingly showed a higher enantiomeric excess for the anti-product due to formation of strong hydrogen bonding between reaction moiety and solvents. In contrast, methanol-assisted reactions resulted in a racemic mixture, consistent with experimental observations. Results reported in the present study contribute to the broader understanding of solvent effects in organic reactions and offer valuable insights for the design of organic reactions. [ABSTRACT FROM AUTHOR]

The photocatalytic degradation of sodium diclofenac, a nonsteroidal anti-inflammatory drug, was carried out comparing the activity of cobalt, nickel, and zinc ferrites as catalysts, using UV radiation and hydrogen peroxide. The materials were characterized by X-ray diffraction and by Fourier-Transform Infrared, UV–Visible and X-ray photoelectron spectroscopies. It was determined that all samples had spinel structure: ZnFe2O4 normal spinel, CoFe2O4 partially inverse spinel and NiFe2O4 inverse spinel. A simulated solution of 40 ppm of sodium diclofenac was completed degraded within 4 h meanwhile 86 to 83% of total organic carbon was obtained. The photocatalytic process take place via radical mechanism. The decrease of samples pH could be attributed to the formation of small acid molecules like oxalic and acetic acid, which are by-products of sodium diclofenac photodegradation. The reaction kinetic was also studied, and the photo-Fenton degradation of sodium diclofenac could be described by first-order model with a linear correlations coefficient R2 > 0.95 in all cases. The information based on kinetic studies can be applied for developing reactors for pollutant elimination, especially for industrial scale. [ABSTRACT FROM AUTHOR]

A chitin/lignin material with defined physicochemical and morphological properties was used as an effective adsorbent of environmentally toxic metals from model systems. Particularly significant is its use in the neutralization of real industrial wastes. The ions Ni 2+ , Cu 2+ , Zn 2+ and Pb 2+ were adsorbed on the functional sorbent, confirming the high sorption capacity of the newly obtained product, primarily due to the presence on its surface of numerous active functional groups from the component biopolymers. The kinetics of the process of ion adsorption from model solution were investigated, and the experimental data were found to fit significantly better to a type 1 pseudo-second-order kinetic model, as confirmed by the high correlation coefficient of 0.999 for adsorption of both nickel(II) copper(II) zinc(II) and lead(II) ions. The experimental data obtained on the basis of adsorption isotherms corresponded to the Langmuir model. The sorption capacity of the chitin/lignin material was measured at 70.41 mg(Ni 2+ )/g, 75.70 mg(Cu 2+ )/g, 82.41 mg(Zn 2+ )/g and 91.74 mg(Pb 2+ )/g. Analysis of thermodynamic parameters confirmed the endothermic nature of the process. It was also shown that nitric acid is a very effective desorbing (regenerating) agent, enabling the chitin/lignin material to be reused as an effective sorbent of metal ions. The sorption abilities of the chitin/lignin system with respect to particular metal ions can be ordered in the sequence Ni 2+

Molecular motor proteins such as Myosin V, Dynein or Kinesin are no ratchets, at least not with a flashing asymmetric potential; the crucial asymmetry is in the dynamical activity. We make that explicit in terms of a simple Markov model, emphasizing the kinetic (and non-thermodynamic) aspects of stochastic transport. The analysis shows the presence of a fluctuation symmetry in that part of the dynamical activity which is antisymmetric under reversal of trailing and leading head of the motor. The direction of the motor motion is determined by it. [ABSTRACT FROM AUTHOR]

Abstract: Interfacial electron transfer at semiconductor nanoparticles is a fundamental process that is relevant to many applications in photocatalysis such as wastewater cleaning, air cleaning and energy production. Fundamental understanding of the dynamic of the electron transfer is of crucial importance for the understanding of the fundamental concepts of photocatalytic processes and hence results in understanding and industrialization of photocatalytic reactions as well as a rational design of the photocatalytic systems. This review summarizes the progress in understanding electron transfer dynamics from semiconductor nanoparticles to the electron acceptor molecules. The approaches to improve the electron transfer efficiency will be also reviewed. Of particular focus will be the advancement of methodology as well as overview of some new highlights in electron transfer reactions at TiO2/liquid interface. [Copyright &y& Elsevier]

Abstract: The synthesis of N-substituted imidazoles via alkylation of imidazole with 1-bromobutane using sonochemical and thermal activations over zeolites (H-ZSM-5, Mordenite, H-Beta and H-Y) is reported. The effect of the acidity and channel size of zeolites on the activity and selectivity of imidazole alkylation was investigated in a liquid phase. The N-alkylimidazoles are important intermediates in the synthesis of pharmaceuticals with antiviral properties. N-alkylimidazoles were obtained in high yields (>80%) as main product (100% selectivity) under mild conditions, ultrasound (US) activation at 333K in only 1h, when Mordenite and NH4Y zeolites were used as catalysts. [Copyright &y& Elsevier]

[Display omitted] This article focuses on the state-of-the-art advancements on the production of isosorbide, a furanic diol exclusively produced via a two-steps dehydrocyclisation of sorbitol; polyol acquired from the catalytic reduction of glucose. Generally, the compound is formed admixed with various types of monocyclic ethers called sorbitans. During the past half century, many researchers tried to explore the underlying mechanistic and kinetic aspects of the reactions involved in its formation with the main objective to increase the selectivity thus avoiding the formation of 2,5-sorbitan by-product. In the intervening years, new energy-saving and environmental-friendly methods have been developed, especially those that involve heterogeneous catalysts or acidic ionic liquids. In order to improve the catalytic activities of catalysts, it is imperative to measure the impact of their intrinsic acidity strength, porosity and surface hydrophobicity on each stage of the formation of bicyclic furanic compound. Additionally, comparative advantageous features of simple protocols involving acidic deep eutectic solvent employed as catalyst in solvent-free microwave-assisted reaction, are highlighted. [ABSTRACT FROM AUTHOR]