Products Of Chemical Reactions Research Articles

Grouping of chemicals for safety assessment: the importance of toxicokinetic properties of salicylate esters

AbstractGrouping of chemicals has been proposed as a strategy to speed up the screening and identification of potential substances of concern among the broad chemical universe under REACH. Such grouping is usually based on shared structural features and should only be used for the prioritization objectives. However, additional considerations (as well as structural similarity) are needed, e.g., mode of action, metabolic pathways, chemical reaction products and physicochemical properties, when regulatory management measures are considered (such as restriction, harmonized classification and labeling). Guidance documents from the European Chemicals Agency (ECHA) recommend considering toxicokinetic information to enhance the robustness of the grouping; however, examples of this approach are lacking. Therefore, this paper shares findings on chemical grouping based on ADME data generated for multiple esters of salicylic acid. These differ with respect to chain length and branching of the alcohol moiety of salicylic acid ester, resulting in a wide range of lipophilicity (LogP 0.21–10.88). Since LogP impacts skin absorption, as well as hydrolysis by carboxylesterases, the bioavailability and thus internal exposure to topically applied salicylate esters can vary considerably. Therefore, we collected skin absorption and metabolism data for 41 salicylates using in vitro testing and in silico models and combined the information to group them according to their potential systemic exposure to the major metabolite, salicylic acid. The results show that, despite a similar general chemical structure, their toxicokinetics vary considerably, indicating the need for better understanding of ADME properties to assess the internal exposure for sound risk assessment.

Study on the activity, phase, thermal decomposition characteristics, microstructure, and chemical element of hardened cement powder under heating temperature of 100°C~1200°C

AbstractThe properties of thermoactivated hardened cement powder (HCP) are of great significance for the recycling and utilization of concrete waste. This paper focuses on heating activation of HCP under the temperature between 100 and 1200°C. The activity, phase changes and microstructure of thermoactivated HCP were analyzed. The results showed that HCP with heating temperature between 1000 and 1200°C showed high activity. Under the conditions of heating activation at 1200°C, water–binder ratio of 0.38 and curing time of 30 days, the compressive strength of the specimen made of HCP reached 17.56 MPa. When the heating temperature is between 700 and 1200°C, CSH gel is gradually decomposed into C2S and C3S. The chemical reaction products of cement and thermoactivated HCP are similar, both containing CaCO3, Ca(OH)2, AFt, Hydrotalcite, etc. Compared to the diffraction peaks of hydrated cement, the diffraction peaks of thermoactivated HCP are broadened and dispersed. The high Ca/Si and Al/Si ratios in the chemical reaction products of thermoactivated HCP are important reasons for the decrease in its mechanical properties.

SULFIDE CAPACITY AND PROPERTIES OF MODIFIED BUCKET SLAGS

Ladle slag during the entire period of iron refining must have a sufficient degree of ability to hold sulfides while simultaneously ensuring the minimization of iron losses. In ladles with recycled cast iron entering the desulphurization department, slags are formed already during the release of cast iron from the blast furnace or pouring from the mixer, which differ significantly from blast furnace slag in terms of physical and chemical properties. The basicity and sulphide capacity of slags decreases, which due to their active mixing with cast iron is accompanied by an increase in sulfur in the metal.The composition of slags, formed from the remains of blast furnace or mixer slags and products of chemical reactions of sulfur removal by injection of mixtures based on lime and magnesium, needs adjustment to increase the sulfide capacity while simultaneously thinning them to prevent excessive losses of iron with the slag. The use of an additional amount of fluidized lime for adjustment leads to an increase in the processing cost. It is proposed to use a slag modifier based on CaO- and Al2O3-containing steel processing waste to reduce the costs of fluidized lime. The rational specific consumption of modifiers was determined depending on the initial composition of ladle slags and the change in their sulfide capacity was calculated using models based on the concept of optical basicity.The change in melting point, viscosity, and melting point of modified ladle slags was determined, and the concentration path of CaO- and Al2O3-containing waste modified with additives was investigated. It is shown that for the typical composition of the ladle slag of cast iron desulfurization plant of PrJSC «Kamet-Stal», the sulfide capacity values ​​range from 1.0.10-4 to 20.0.10-4, which corresponds to blast furnace slags of the CaO-SiO2-MnO-Al2O3-MgO system with increased desulfurizing ability. The change in the amount of the solid fraction in the final slag in the course of refining and the effect of the basicity of the modified slag on the sulfur distribution coefficient in non-stationary temperature conditions were determined. With the application of the linear programming method, the range of rational chemical composition of ladle slag for the conditions of cast iron desulfurization plant of PrJSC «Kamet-Stal» was determined. Modified ladle slag with a basicity of 1.11-1.41 and a content of 40-51% CaO; 36-51 %SiO2 and 6-21 %Al2O3 are proposed to be considered as satisfying the given range of selected metallurgical properties.

COMBUSTION OF HYDROGEN IN OXYGEN-STEAM MIXTURE FOR INCREASING THE STEAM TEMPERATURE OF POWER PLANTS

In the work the problems that arise at combustion of hydrogen in oxygen-steam mixture for the purpose of combustion products (steam) mixing for heating steam, which is planned to be used in steam turbines of power plants were researched. The main problem is the formation of underburning H2 and, accordingly, the presence of O2, which have a negative effect on metals, and it will also prevent steam condensation in the condenser was determined. For solve this problem, calculations of the equilibrium concentrations of chemical reaction products in the combustion zone depending on the amount of ballast steam added to the oxidizer (oxygen) for the initial conditions: T0=528 K, p=0.1 MPa; T0=​​528 K, p=3.1 MPa; T0=​​584 K, p=10 MPa were made. The corresponding adiabatic temperatures were calculated. The dilution of the oxidant (oxygen) with steam significantly decreases the adiabatic temperature (Tb) and reduces the equilibrium concentrations of other substances in the combustion zone, but at the same time the laminar flame propagation velocity (SL) also significantly decreases was established. It is important when a certain concertation of ballast steam is achieved (the final percentage is determined by the design of the burner) there will be a sharp deterioration of combustion or even the formation of a flame will be impossible. The principal design of the hydrogen-oxygen-steam combustion chamber was proposed. The necessity of heating oxygen and hydrogen and the principle of determining the pressure under which it is advisable to supply oxygen and hydrogen to ensure the maximum intensification of mixing first of oxygen and steam, and then of the formed mixture and hydrogen, were substantiated. Bibl. 20, Fig. 5, Table 3.

Effects of Frequency on the Performance of Ultrasonic Vibration Assisted Chemical Mechanical Polishing for Sapphire

Sapphire (Al2O3) is renowned for its exceptional properties, yet its unique natural presents a surface processing challenge. To enhance the polishing quality and efficiency, the sapphire ultrasonic vibration assisted chemical mechanical polishing (UV-CMP) has been proposed. This paper employs computational fluid dynamics (CFD) simulation and polishing experiments to investigate the action and mechanism of ultrasonic frequency on sapphire UV-CMP. The CFD simulation reveals that an increase in frequency can effectively elevate the fluid velocity, pressure, and cavitation. The enhancement in pressure, Z-direction, and resultant velocity has a positive impact on the cutting ability and utilization rate of nano-abrasives. A high frequency can enhance the physical fields of slurry, but it suppresses the growth of cavitation bubbles, and is detrimental to the number and size of abrasive particles. The best processing performance of sapphire UV-CMP is obtained at 40 kHz due to coordinated physicochemical interactions. X-ray photoelectron spectroscpy proves the product of solid-solid chemical reaction between nano-SiO2 and sapphire is softer Al2Si2O7 instead of Al2SiO5, which is beneficial to the material removal. This article provides theoretical and practical guidance for sapphire UV-CMP.

Molecular modelling of luciferyl adenylate deprotonation in the active site of Photinus pyralis luciferase

Firefly bioluminescence is a product of chemical reactions that involve luciferin chromophore oxidation in the active site of luciferase proteins. We perform a series of classical molecular dynamic simulations and combined quantum and molecular mechanics (QM/MM) calculations to expose the molecular mechanism of C4 carbon atom deprotonation in luciferyl adenylate molecule. QM/MM calculations confirm that ND-protonated His245 residue is a suitable proton acceptor in the wild-type Photinus pyralis luciferase. Classical molecular dynamic simulations reveal oxygen-binding cavities inside the protein including the one located close to the C4 atom of luciferin. In mutant forms that lack direct interactions with the His245 side chain, a proton wire comprising water molecules stimulates either protonation of the phosphate group of the luciferyl adenylate forming an unstable intermediate or keto–enol tautomerisation of luciferin. The comparison of the ionisation potentials of molecular systems with the ‘deprotonated’ C4 carbon atom revealed that the ionisation energy for the enol tautomeric form is close to the system with the His245 proton acceptor. Thus, the existence of the keto–enol tautomerisation channel might explain bioluminescence in case of the absence of the amino acid proton acceptor.

A Review of Catalyst Integration in Hydrothermal Gasification

Industrial scale-up of hydrothermal supercritical water gasification process requires catalytic integration to reduce the high operational temperatures and pressures to enhance controlled chemical reaction pathways, product yields, and overall process economics. There is greater literature disparity in consensus on what is the best catalyst and reactor design for hydrothermal gasification. This arises from the limited research on catalysis in continuous flow hydrothermal systems and rudimentary lab-scale experimentation on simple biomasses. This review summarizes the literature status of catalytic hydrothermal processing, especially for continuous gasification and in situ catalyst handling. The rationale for using low and high temperatures during catalytic hydrothermal processing is highlighted. The role of homogeneous and heterogeneous catalysts in hydrothermal gasification is presented. In addition, the rationale behind certain designs and component selection for catalytic investigations in continuous hydrothermal conversion is highlighted. Furthermore, the effect of different classes of catalysts on the reactor and reactions are elaborated. Overall, design and infrastructural challenges such as plugging, corrosion, agglomeration of the catalysts, catalyst metal leaching, and practical assessment of catalyst integration towards enhancement of process economics still present open questions. Therefore, strategies for catalytic configuration in continuous hydrothermal process must be evaluated on a system-by-system basis depending on the feedstock and experimental goals.

ULTRASOUND IN CATALYSIS

The results of studied on the use of ultrasound in catalyst synthesis and processing are summarised. It is demonstrated that exposure to ultrasound can regulate the textural and structural characteristics of catalysts by varying exposure time and the amplitude of ultrasonic radiation. Optimisation of the conditions of ultrasonic treatment of the catalysts is determined to provide improvement of their physicochemical properties. This allows achieving higher reagents conversion and selectivity of the formation of target products in various chemical reactions. Examples of ultrasound application from the viewpoint of following the green chemistry principles are considered. It is shown that ultrasound application in organic synthesis promotes improvement of chemical process characteristics and reduces reaction time.

Multi-armed bandit algorithm for sequential experiments of molecular properties with dynamic feature selection.

Sequential optimization is one of the promising approaches in identifying the optimal candidate(s) (molecules, reactants, drugs, etc.) with desired properties (reaction yield, selectivity, efficacy, etc.) from a large set of potential candidates, while minimizing the number of experiments required. However, the high dimensionality of the feature space (e.g., molecular descriptors) makes it often difficult to utilize the relevant features during the process of updating the set of candidates to be examined. In this article, we developed a new sequential optimization algorithm for molecular problems based on reinforcement learning, multi-armed linear bandit framework, and online, dynamic feature selections in which relevant molecular descriptors are updated along with the experiments. We also designed a stopping condition aimed to guarantee the reliability of the chosen candidate from the dataset pool. The developed algorithm was examined by comparing with Bayesian optimization (BO), using two synthetic datasets and two real datasets in which one dataset includes hydration free energy of molecules and another one includes a free energy difference between enantiomer products in chemical reaction. We found that the dynamic feature selection in representing the desired properties along the experiments provides a better performance (e.g., time required to find the best candidate and stop the experiment) as the overall trend and that our multi-armed linear bandit approach with a dynamic feature selection scheme outperforms the standard BO with fixed feature variables. The comparison of our algorithm to BO with dynamic feature selection is also addressed.

One-pot approach for acoustic directed assembly of metallic and composite microstructures by metal ion reduction

One-pot approach for acoustic directed assembly of metallic and composite microstructures by metal ion reduction

Перспектива застосування хімічних окислювачів для нейтралізації та дегазації фосфіну в морській фумігації вантажів

ABSTRACT. The transportation of grains, legumes and other regulated articles requires mandatory fumigation. Toxicological safety of fumigation team and crewmembers of the sea merchant fleet is a mandatory condition for fumigation. Hazardous waste is generated on board the ship during the work of the fumigation team. The development of a technique for phosphine residues degassing in containers, fumi-sleeves, etc. on board of a ship is an important scientific and applied task. Аim of the research. Study the possibility of application of well-known oxidizers (hydrogen peroxide, chloramine, ozone, potassium permanganate) for neutralizing and degassing of phosphine and phosphine-containing poison fumigants in marine cargo fumigation, conduct an analysis of redox reactions of degassers with phosphine and assess the toxicity of chemical reaction products. Materials and Мethods. The analysis of phosphine content was carried out by the method of stationary gas chromatography on the Tsvet-160 chromatograph, as well as by the method of electrochemical analysis using the Pac III – PH3, Accuro (Germany) and ToxyPro (USA) portable devices. An analytical review of the literature was performed, laboratory-experimental and field studies for degassing of phosphine and poisonous fumigants during marine fumigation of grain and fodder cargoes were conducted on ships of the bulk fleet and in the seaports of Odesa, Chornomorsk, and Yuzhne. The results. It is shown that, contrary to existing methods, water and its soap solutions do not have destructive and neutralizing properties in relation to phosphine and phosphine-containing preparations. Their use for phosphine degassing is impractical and dangerous. Conclusions. The application of aqueous solutions of typical oxidizers (chlorine, hydrogen peroxide, ozone, and potassium permanganate) for degassing used containers from phosphine-containing preparations and fumigants on board ships can be recommended for use in national and international practice of maritime fumigation of cargo. Keywords: maritime fumigation, poison fumigants, phosphine, chemical oxidizers, degassing of containers from fumigants, simultaneous extinguishing and degassing of fumi-sleeves from phosphine fumigants

Quantifying Chemical Reactions and Interfacial Properties at Buried Polymer/Polymer Interfaces.

Maleic anhydride (MAH)-modified polymers are used as tie layers for binding dissimilar polymers in multilayer polymer films. The MAH chemistry which promotes adhesion is well characterized in the bulk; however, only recently has the interfacial chemistry been studied. Sum frequency generation vibrational spectroscopy (SFG) is an interfacial spectroscopy technique which provides detailed information on interfacial chemical reactions, species, and molecular orientations and has been essential for characterizing the MAH chemistry in both nylon and ethyl vinyl alcohol copolymer (EVOH) model systems and coextruded multilayer films. Here, we further characterize the interfacial chemistry between MAH-modified polyethylene tie layers and both EVOH and nylon by investigating the model systems over a range of MAH concentrations. We can detect the interfacial chemical reaction products between MAH and the barrier layer at MAH concentrations of ≥0.022 wt % for nylon and ≥0.077 wt % for EVOH. Additionally, from the concentration-dependent reaction reactant/product SFG peak positions and the product imide or ester/acid C═O group tilt angles extracted from the polarization-dependent SFG spectra, we quantitatively observe concentration-dependent changes to both the interfacial chemistry and interfacial structure. The interfacial chemistry and molecular orientation as a function of MAH concentration are well correlated with the adhesion strength, providing important quantitative information for the future design of MAH-modified tie layers for a variety of important applications.

Особенности строительного контроля компонентов и конструкции полимерных зон деформационных швов мостовых сооружений

The article considers the construction control peculiarities of components and design of transition polymer zones of bridge structures expansion joints. The authors have examined the transition zones of expansion joints of in-use bridge structures constructed with polymer concrete. The study revealed the lack of regulatory requirements at the national standardization system documents level. The authors confirmed the possibility of binder composition identification at the organisation of construction control of supplied products in accordance with the requirements of design documentation. The authors also confirmed the possibility of determining the products of chemical reaction during curing of polymer concrete in the transition zone of bridge expansion joints. The authors used a low viscosity liquid epoxy resin based on bisphenol with the inclusion of an amine-type hardener to produce a polymer-concrete mixture. When the components are mixed, a composition is obtained that cures and, when bound to mineral aggregate, provides the product with high strength, water resistance, wear resistance and good adhesion to various substrates. The material obtained for bridge constructions is safe for the environment and does not react with various agents. The method of infrared spectroscopy allows identifying the initial substances and reaction products with the probability of coincidence from 70 to 97%.

Product-specific reaction kinetics in continuous uniform supersonic flows probed by chirped-pulse microwave spectroscopy.

Experimental studies of the products of elementary gas-phase chemical reactions occurring at low temperatures (<50K) are very scarce, but of importance for fundamental studies of reaction dynamics, comparisons with high-level quantum dynamical calculations, and, in particular, for providing data for the modeling of cold astrophysical environments, such as dense interstellar clouds, the atmospheres of the outer planets, and cometary comae. This study describes the construction and testing of a new apparatus designed to measure product branching fractions of elementary bimolecular gas-phase reactions at low temperatures. It combines chirped-pulse Fourier transform millimeter wave spectroscopy with continuous uniform supersonic flows and high repetition rate laser photolysis. After a comprehensive description of the apparatus, the experimental procedures and data processing protocols used for signal recovery, the capabilities of the instrument are explored by the study of the photodissociation of acrylonitrile and the detection of two of its photoproducts, HC3N and HCN. A description is then given of a study of the reactions of the CN radical with C2H2 at 30K, detecting the HC3N product, and with C2H6 at 10K, detecting the HCN product. A calibration of these two products is finally attempted using the photodissociation of acrylonitrile as a reference process. The limitations and possible improvements in the instrument are discussed in conclusion.

Effect of leakage of volatile synthesis products on silicon carbide yield in an electrothermal fluidized bed reactor

Effect of leakage of volatile synthesis products on silicon carbide yield in an electrothermal fluidized bed reactor

A coupled physical–chemical model for mass transfer considering damage evolution: Sulfate ions transport in a cement-based material as an example

A coupled physical–chemical model for mass transfer considering damage evolution: Sulfate ions transport in a cement-based material as an example

Inhibitory Effects of the Polyphenols from the Root of Rhizophora apiculata Blume on Fatty Acid Synthase Activity and Human Colon Cancer Cells.

Marine mangrove vegetation has been traditionally employed in folk medicine to address various ailments. Notably, Rhizophora apiculata Blume has exhibited noteworthy properties, demonstrating efficacy against cancer, viruses, and bacteria. The enzyme fatty acid synthase (FAS) plays a pivotal role in de novo fatty acid synthesis, making it a promising target for combating colon cancer. Our study focused on evaluating the FAS inhibitory effects of both the crude extract and three isolated compounds from R. apiculata. The n-butanol fraction of R. apiculata extract (BFR) demonstrated a significant inhibition of FAS, with an IC50 value of 93.0 µg/mL. For inhibition via lyoniresinol-3α-O-β-rhamnopyranoside (LR), the corresponding IC50 value was 20.1 µg/mL (35.5 µM). LR competitively inhibited the FAS reaction with acetyl-CoA, noncompetitively with malonyl-CoA, and in a mixed manner with NADPH. Our results also suggest that both BFR and LR reversibly bind to the KR domain of FAS, hindering the reduction of saturated acyl groups in fatty acid synthesis. Furthermore, BFR and LR displayed time-dependent inhibition for FAS, with kobs values of 0.0045 min-1 and 0.026 min-1, respectively. LR also exhibited time-dependent inhibition on the KR domain, with a kobs value of 0.019 min-1. In human colon cancer cells, LR demonstrated the ability to reduce viability and inhibit intracellular FAS activity. Notably, the effects of LR on human colon cancer cells could be reversed with the end product of FAS-catalyzed chemical reactions, affirming the specificity of LR on FAS. These findings underscore the potential of BFR and LR as potent FAS inhibitors, presenting novel avenues for the treatment of human colon cancer.

SYNTHESIS OF CALCIUM SILICATE MATERIALS FROM THE RESIDUAL WASTE SLUDGE OF A WATER-PURIFICATION PLANT

SYNTHESIS OF CALCIUM SILICATE MATERIALS FROM THE RESIDUAL WASTE SLUDGE OF A WATER-PURIFICATION PLANT

Effect of vacuum–vibration–compaction molding on the properties and performances of polymer-modified cementitious material

Effect of vacuum–vibration–compaction molding on the properties and performances of polymer-modified cementitious material

Process and mechanism for synergistic treatment of spent carbon cathode and red mud by hydrothermal acid-leaching

Process and mechanism for synergistic treatment of spent carbon cathode and red mud by hydrothermal acid-leaching