Reaction Probability Research Articles

Asymmetric Synthesis of Dihydropyrimidinethione Podand in the Presence of C2‐Symmetric Bis(Hydroxy)Proline‐Containing Amides

AbstractA stereoselective Biginelli reaction involving a CH‐active podand, thiourea, and benzaldehyde was carried out using C2‐symmetric bis(hydroxy)proline‐containing amides as chiral inducers. The target dihydropyrimidinethione‐containing podand was obtained with an enantiomeric excess of 65–75 % and a yield of 58 % under mild conditions. It was established that in the process of asymmetric induction the value of ee depended on the presence of OH group in the proline fragment and of the linker structure in the chiral inducer molecule, in particular, on the presence of asymmetric carbon atoms and the movability of the single bond between them in the linker itself. Based on experimental data, one of the probable reaction mechanisms confirming the special role of the L‐proline or trans‐4‐hydroxyproline fragments in asymmetric induction has been proposed. The developed technique for obtaining an active tuberculostatic agent expands the possibilities for using C2‐symmetric chiral inducers in asymmetric catalysis and is of interest for the synthesis of enantiomerically pure compounds of similar structure.

Reactant-Product Decoupling Technique Using the Intermediate Coordinate Method.

Although the reactant-product decoupling (RPD) technique was proposed over two decades ago, it remains an efficient approach for calculating product state-resolved information on some simple direct reactions using the quantum wave packet method. In the past, usually the RPD technique employed the collocation method to transform the wave function between reactant and product arrangements, which requires quite large computational efforts. In this work, the intermediate coordinate (IC) method is employed to realize the RPD technique. Numerical examples demonstrate that this new IC RPD (IRPD) technique has superior computational efficiency compared with the original method employing the collocation method. Especially, the new IRPD technique significantly saves disk space and computer memory. To illustrate the features of our new method, the total reaction probabilities of the H + H2, H + Br2, and F + H2 reactions with J = 0 and the differential cross sections of the H + H2 and F + H2 reactions at a series of collision energy are calculated and presented. With this efficient and effective new RPD technique, the Li + HF reaction, which involves sharp resonances with long-range wave functions in the van der Waals wells in both the reactant and product arrangements, is also calculated with several J at the product state-resolved level to reveal the ability of the RPD technique for describing resonance wave functions. With these numerical examples, it is found that, for the reaction with resonances, the RPD approach should be applied carefully. Otherwise, it is very possible that the resonances could disappear with the application of the RPD technique.

A new global potential energy surface of CaH2 system constructed with neural network method and dynamics studies of the Ca(4s21S) + H2 reaction

A new global potential energy surface (PES) for the ground state of CaH2 system was constructed by using neural network method. This paper provides a comprehensive discussion on the topographical characteristics of the PES and the spectral properties of stationary points. Furthermore, a time-dependent wave packet method was used to perform the dynamics studies on the Ca(4 s2 1S) + H2 reaction based on the newly constructed PES. Some meaningful dynamics results are reported, including reaction probabilities, integral cross sections and differential cross sections. In addition, the reaction mechanism of the Ca(4 s2 1S) + H2 reaction was discussed in detail.

The bond energy of UN+: Guided ion beam studies of the reactions of U+ with N2 and NO.

A guided ion beam tandem mass spectrometer was used to study the reactions of U+ with N2 and NO. Reaction cross sections were measured over a wide range of energy for both systems. In each reaction, UN+ is formed by an endothermic process, thereby enabling the direct measurement of the threshold energy and determination of the UN+ bond dissociation energy. For the reaction of U+ + N2, a threshold energy (E0) of 4.02 ± 0.11eV was measured, leading to D0 (UN+) = 5.73 ± 0.11eV. The reaction of U+ + NO yields UO+ through an exothermic, barrierless process that proceeds with 94 ± 23% efficiency at the lowest energy. Analysis of the endothermic UN+ cross section in this reaction provides E0 = 0.72 ± 0.11eV and, therefore, D0 (UN+) = 5.78 ± 0.11eV. Averaging the values obtained from both reactions, we report D0 (UN+) = 5.76 ± 0.13eV as our best value (uncertainty of two standard deviations). Combined with precise literature values for the ionization energies of U and UN, we also derive D0 (UN) = 5.86 ± 0.13eV. Both bond dissociation energies agree well with high-level theoretical treatments in the literature. The formation of UN+ in reaction of U+ with NO also exhibits a considerable increase in reaction probability above ∼3eV. Theory suggests that this may be consistent with the formation of UN+ in excited quintet spin states, which we hypothesize are dynamically favored because the number of 5f electrons in reactants and products is conserved.

Synthesis and application of Cu-CaTiO3-GO ternary composite: A new visible-light active multifunctional photocatalyst efficient towards antibiotic cefixime degradation and H2 evolution reaction

To combat the issues of energy scarcity and environmental pollution, a visible-light responsive, ternary photocatalyst (Cu-CaTiO3-GO) was fabricated, by photo-depositing Cu nanoparticles over a CaTiO3-GO binary composite. The physicochemical characteristics of Cu-CaTiO3-GO were investigated using XRD, HR-TEM, FE-SEM, EDS-mapping XPS, Raman, FT-IR, BET, EIS, UV–vis DRS, and PL techniques. In comparison with pristine CaTiO3, and binary composites (Cu-CaTiO3, CaTiO3-GO), the ternary hybrid exhibited superior photocatalytic activity for H2generation as well as antibiotic cefixime (CFX) degradation. Under LED light, the rate of H2 generation over Cu-CaTiO3-GO accumulated to 57.69 mmolh−1, while the photodegradation efficiency for CFX reached 94.1 % in 100 min with 53.4 % of TOC removal. The upgraded performance is credited to synergistic effects of Cu NPs (SPR effect), CaTiO3 (specialized cuboid-like morphology), and GO (high conductivity), co-existing in the trio-hybrid, which resulted in a greatly increased surface area, an expanded spectral response range, a stronger adsorption property, efficient charge migration and separation extent. Ternary catalyst performed well even in the 4 recycling tests (retaining 79.4 % CFX removal and 52.51 mmolh−1 H2 evolution efficiency). In Cu-CaTiO3-GO system, the electron transport channel (Cu → CaTiO3 → GO) with adequate band potentials effectively supports both photocatalytic oxidation and reduction. Photoelectrons are enriched and transferred by plasmonic Cu, and then captured by GO, an e- sink. This maximizes composite photo redox capability, rapidly generating active radicals (OH), and (O2-), degrading CFX to simpler molecules and reducing proton to H2. The effectiveness of Cu-CaTiO3-GO was even tested in the real water matrices. Besides, degradation intermediates of CFX were elucidated using LC-MS, and the decomposition pathway was suggested. Finally, the probable photocatalytic reaction mechanism was deduced for both the degradation and H2 generation processes. The current study proposes a non-noble transition metal-based perovskite-type photocatalytic material for both clean energy generation and wastewater treatment.

Co-pyrolysis characteristic of sugarcane waste with polyethylene terephthalate: thermal decomposition, product distribution, synergistic effect, and kinetics analysis.

This work has focused on the co-pyrolysis of sugarcane waste (SW) with polyethylene terephthalate (PET) to gain insight on its thermal decomposition, product distribution, kinetics, and synergistic effect. SW and PET were blended at different ratios (100:0, 80:20, 60:40, 40:60, and 0:100), and the Coats-Redfern method was used to determine the kinetics parameters. To ascertain the synergistic effect between SW and PET, product yields and composition of chemicals were compared with the synergistic effect of the individual components of pyrolysis. The bio-oil yield was significant at 60% of PET, with a difference of 19.41 wt% compared to the theoretical value. The synergistic impact of SW:PET on ester formation and acid compound inhibition was the most dominant at the 60:40 ratio. The kinetics analysis revealed that the diffusion mechanism, power law, and order of reactions were the most probable reaction models that can explain the pyrolysis of SW, and PET, and their blends. The resultant co-pyrolysis oil contained slightly larger hydrogen and carbon contents with low oxygen, and sulphur, and nitrogen contents, which improved the quality of the bio-oil. The results of this work could be used as a guide in selecting proper reaction conditions with optimal synergy during the co-pyrolysis process.

Impact of Geometric Phase on Dynamics of Complex-Forming Reactions: H + O2 → OH + O.

Reaction dynamics on the ground electronic state might be significantly influenced by conical intersections (CIs) via the geometric phase (GP), as demonstrated for activated reactions (i.e., the H + H2 exchange reaction). However, there have been few investigations of GP effects in complex-forming reactions. Here, we report a full quantum dynamical study of an important reaction in combustion (H + O2 → OH + O), which serves as a proving ground for studying GP effects therein. The results reveal significant differences in reaction probabilities and differential cross sections (DCSs) obtained with and without GP, underscoring its strong impact. However, the GP effects are less pronounced for the reaction integral cross sections, apparently due to the integral of the DCS over the scattering angle. Further analysis indicated that the cross section has roughly the same contributions from the two topologically distinct paths around the CI, namely, the direct and looping paths.

Thermodynamics of cordierite formation during firing of water-permeable ceramics

The analysis of the influence of an increase in firing temperature on the thermodynamic possibilities of solid-phase chemical reactions in the MgO–Al2O3–SiO2 system in the direction of cordierite formation has been conducted. The thermodynamic direction of solid-phase reactions in the MgO–Al2O3–SiO2 system allows determining rational firing temperatures of materials containing cordierite for the manufacture of products for various purposes. During low-temperature firing (up to 1200 K) of finely dispersed masses based on talc-clay-alumina compositions, materials with high open porosity but low strength characteristics can be obtained. This is because the reactive sintering mainly occurs due to reactions forming intermediates for cordierite synthesis and incomplete processes of destruction in natural mineral raw materials. In the firing temperature range of 1200–1500 K, the thermodynamic probability of reactions immediately via several cordierite formation mechanisms increases, which should limit the growth of individual crystals while increasing their quantity. This should positively affect the strength and heat resistance of materials due to low values of the thermal coefficient of linear expansion. Firing temperatures of 1500–1659 K correspond to the limits for cordierite formation and contribute to the consolidation of the material with a change in the nature of porosity from open to closed. Exceeding firing temperatures above 1659 K results in the thermodynamic instability of the cordierite-corundum phase combination and can lead to the formation of defects due to the appearance of a significant amount of melt in the phase composition of the material.

Dissipative Particle Dynamics Study on the Phase Region of Spatial Gradient Materials Produced by Photoinduced Isomerization

AbstractSpatial gradient materials occupy an important research position in the field of functional materials with their unique porous structure. Gradient changes in pore size and density distribution have received extensive attention in the fields of biomimetic and smart materials. The gradient transition law is mathematically related to the driving force of isomerization reaction and component phase separation. In this study, a dissipative particle dynamics simulation is used to introduce photoisomerization reactions into the system. Lambert's law is used to construct a reaction model for the variation of light intensity with irradiation depth, and a gradient structure with a spatial transition law is obtained. The effects of the extinction coefficient ε, the initial reaction probability Pr0, and the interactions α(A,B) between the isomerized molecules as well as the viscosity on the formation of the gradient structure are investigated in detail. Furthermore, the mathematical proportionality between the size of the phase region and interfacial energy of the two phases is elucidated. This study provides preliminary computational insights into the factors affecting the photoinduced phase separation process of polymeric gradient materials. It may help to develop effective strategies to improve the phase separation and properties of polymer gradient materials in subsequent studies.

Spin-Dependent Stereochemistry: A Nonadiabatic Quantum Dynamics Case Study of S + H2 → SH + H Reaction.

We study the spin-dependent stereodynamics of the S + H2 → SH + H reaction by using full-dimensional quantum dynamics calculations with zero total nuclear angular momentum along the triplet 3A″ states and singlet 1A' states. We find that the interplay between the electronic spin direction and the molecular geometry has a measurable influence on the singlet-triplet intersystem crossing reaction probabilities. Our results show that for some incident scattering angles in the body-fixed frame, the relative difference in intersystem crossing reaction probabilities (as determined between spin up and spin down initial states) can be as large as 15%. Our findings are an ab initio demonstration of spin-dependent nonadiabatic dynamics, which we hope will shine light as far as understanding the chiral-induced spin selectivity effect.

State-to-State Quantum Dynamics Study of Intramolecular Isotope Effects on Be(1S) + HD (v0 = 2, j0 = 0) → BeH/BeD + H/D Reaction.

The dynamic mechanisms and intramolecular isotope effects of the Be(1S) + HD (v0 = 2, j0 = 0) → BeH/BeD + H/D reaction are studied at the state-to-state level using the time-dependent wave packet method on a high-quality potential energy surface. This reaction can proceed along the indirect pathway that features a barrier and a deep well or the smooth direct pathway. The reaction probabilities, total and state-resolved integral cross sections, and differential cross sections are analyzed in detail. The calculated dynamics results show that both of the products are mainly formed by the dissociation of a collinear HBeD intermediate when the collision energy is slightly larger than the threshold. As the collision energy increases, the BeH + D channel is dominated by the direct abstraction process, whereas the BeD + H channel mainly follows the complex-forming mechanism.

Prepared Sulfonic-Acid-Based Ionic Liquid for Catalytic Conversion of Furfuryl Alcohol to Ethyl Levulinate.

Efficient utilization of Brønsted acids has been advanced through the synthesis of a novel pyridinium propyl sulfonic acid ionic liquid catalyst, [PSna][HSO4]. Employing niacin and 1,3-propanesulfonic lactone, the synthesis aimed to achieve a catalyst that combines atom-efficiency with stability. Optimal catalytic activity was demonstrated at a temperature of 110 °C over a 2 h reaction time, resulting in a furfuryl alcohol conversion and ethyl levulinate yield of 97.79% and 96.10%, respectively. Notably, the extraction and recovery of [PSna][HSO4] exhibited commendable repeatability with up to five cycles, maintaining furfuryl alcohol conversion and ethyl levulinate yield at 93.74% and 88.17%, which highlights the catalyst's durability. Density flooding theory (DFT) calculations were employed to determine the most probable reaction pathways and identify all possible transition states and the reaction energy barriers overcome at each step of the reaction.

Effect of Different Temperature and Nuclear Data Libraries in Criticality Calculations of 300 MWt Molten Salt Reactor

The Molten Salt Reactor (MSR) is a type of reactor in which coolant and fuel are blended with liquid salts. Liquid fuel enhances heat transfer and temperature control, establishing the MSR as one of the Generation IV reactor types. This study aims to analyze the impact of temperature variations on MSR reactor criticality and evaluate the effect of different nuclear data libraries, namely JENDL 3.2, JENDL 3.3, and JENDL 4.0, in neutron analysis. The observed temperature variations are 600 K, 700 K, 833 K, 903 K, and 1000 K. The analysis spans low to operational temperatures to comprehend reactor performance under differing thermal conditions. The study is conducted on a 300 MWTh MSR design, utilizing SRAC2006 with PIJ and CITATION modules for calculations. The results reveal the impact of temperature variations and nuclear data library disparities on reactor criticality. The outcomes demonstrate that higher temperatures correspond to lower values of the effective multiplication factor. At lower temperatures, neutrons experience greater moderation compared to higher temperatures. As a result, a higher number of thermal neutrons influences an increased probability of fission reactions within the reactor. Different nuclear data libraries also yield varied criticality values due to differing cross-sectional areas and quantities of data within each JENDL library. JENDL 4.0 generates the highest criticality value, attributed to elevated cross-sectional regions of each respective nuclear data entry and a greater quantity of nuclear data entries than JENDL 3.2 and JENDL 3.3.

Clinical Profile of Patients with Lichenoid Drug Eruption: A Observational Study.

Lichenoid drug eruption (LDE) is an uncommon cutaneous adverse drug reaction, where a variety of drugs used in day-to-day clinical practice have been implicated. To describe the clinico-demographic characteristics of patients with LDE and to identify the most likely drugs involved. In this prospective, observational study, consecutive patients with LDE presenting to the dermatology department of a tertiary teaching hospital were included. The clinico-demographic profile of patients with LDE and implicated drugs was noted. Treatment of drug reaction along with outcome was also documented. Naranjo adverse drug reaction probability scale was used for causality assessment of the drug reactions. A thorough literature review on LDE was also undertaken due to the paucity of existing literature. A total of 15 patients (11 males and 4 females) with LDE were evaluated. Their age ranged from 37 to 61 years, with a mean of 51.53 ± 7.59 years. Anti-hypertensive medications (40%) were the most common culprit agent, followed by antitubercular drugs (33.4%), anti-diabetic agents (13.3%), and others (13.3%). The latent period (time from drug initiation to the appearance of a cutaneous eruption) varied from 15 days to 6 months (mean 2.2 months). Cutaneous involvement was generalized in 73.4% and photo-distributed lesions in 26.6%. Drug provocation test was done to identify the culprit drug. According to the Naranjo adverse drug reaction probability scale, one-third of LDEs were "definite," whereas two-thirds were designated as "probable." LDE is more common in the elderly population. The latent period is comparatively longer in LDE than in other common drug reactions. Prompt recognition and withdrawal of suspected drug are essential to minimize disease morbidity.

Membrane localization accelerates association under conditions relevant to cellular signaling

Translocation of cytoplasmic molecules to the plasma membrane is commonplace in cell signaling. Membrane localization has been hypothesized to increase intermolecular association rates; however, it has also been argued that association should be faster in the cytosol because membrane diffusion is slow. Here, we directly compare an identical association reaction, the binding of complementary DNA strands, in solution and on supported membranes. The measured rate constants show that for a 10-µm-radius spherical cell, association is 22- to 33-fold faster at the membrane than in the cytoplasm. The kinetic advantage depends on cell size and is essentially negligible for typical ~1 µm prokaryotic cells. The rate enhancement is attributable to a combination of higher encounter rates in two dimensions and a higher reaction probability per encounter.

Photocatalytic degradation of enrofloxacin with CoAl-LDH mediated persulfate system: Efficiency evaluations and reaction pathways

Residual enrofloxacin (ENR) exposed in aqueous environments is challenging to the ecosphere. In this work, a layered double hydroxide CoAl-LDH was used to activate the common oxidizing agent persulfate (PS) for photodegradation of ENR, and the degradation pathways of ENR were scrutinized and elucidated. The results indicated that, under the optimal conditions obtained through orthogonal experiments, even though the degradation rate of ENR was as high as 97.72%, the removal of total organic carbon (TOC) from the system was only about 30%. Eleven probable reaction pathways were categorized, and thirty-one types of intermediates were identified in participating in the complex degradation process. The major products of ENR were P4 (C17H20FN3O3), P22 (C19H22FN3O4), P19 (C17H18FN3O3), which are mainly derived from the cleavage of the piperazine groups and quinolone rings. Density functional theory (DFT) calculations of the Fukui index for ENR revealed that the two N atoms in the piperazine ring were the core reactive sites in triggering the degradation chains, which were sensitive for electrophilic attack by the dominant radicals (•OH and SO4•-) generated from the composite PS-UV-CoAl-LDH system.

Hollow Porous Structures for Improving the Sensitivity of Colorimetric Array Gas Sensors

AbstractDetecting volatile organic compounds (VOCs) in exhaled breath is a promising research area for disease diagnosis. Mass transfer behavior plays a crucial role in determining the detection performance of VOCs. However, the high mobility of exhaled breath poses a substantial challenge for the mass transfer process. Here, the distinct mass transfer behavior of mobile gaseous molecules is discovered by employing the schlieren imaging technique to visualize gas flow. The results demonstrate that hollow porous structures exhibit a higher gas flow flux than solid film and microporous structures, thereby generating a sufficient probability of contact reactions for mobile gaseous molecules. The proposed colorimetric array sensors offer enhanced sensitivity and stability for detecting mobile gaseous molecules. The discovery will serve as a foundational milestone is anticipated in elucidating the behavior of gas mass transfer and promoting its potential application in disease detection through the analysis of human exhaled breath.

Accurate Reaction Probabilities for Translational Energies on Both Sides of the Barrier of Dissociative Chemisorption on Metal Surfaces.

Molecular dynamics simulations are essential for a better understanding of dissociative chemisorption on metal surfaces, which is often the rate-controlling step in heterogeneous and plasma catalysis. The workhorse quasi-classical trajectory approach ubiquitous in molecular dynamics is able to accurately predict reactivity only for high translational and low vibrational energies. In contrast, catalytically relevant conditions generally involve low translational and elevated vibrational energies. Existing quantum dynamics approaches are intractable or approximate as a result of the large number of degrees of freedom present in molecule-metal surface reactions. Here, we extend a ring polymer molecular dynamics approach to fully include, for the first time, the degrees of freedom of a moving metal surface. With this approach, experimental sticking probabilities for the dissociative chemisorption of methane on Pt(111) are reproduced for a large range of translational and vibrational energies by including nuclear quantum effects and employing full-dimensional simulations.

Highly efficient supported bimetallic Au‐Pd catalysts for oxidative esterification of methacrolein to methyl methacrylate

AbstractAu‐Pd alloy particles supported on TiO2 were synthesized by the sol‐immobilized method and their confirmation was achieved through transmission electron microscope (TEM) and energy dispersive spectrometer (EDS) mapping. The samples were subjected to oxidative esterification of methacrolein with methanol to methyl methacrylate (MMA). Notably, a remarkable enhancement of catalytic performance was found in the presence of Pd. Among the samples tested, the sample Au0.25Pd0.75/TiO2 exhibited the highest catalytic performance. The interaction between Au and Pd demonstrated a synergistic effect, with Pd contributing to the stability of Au nanoparticles and strengthening the production of active oxygen species, which facilitated the efficient removal of hydrogen from intermediate hemiacetal. Furthermore, a probable reaction mechanism was proposed to explain these observations.

Deprescribing in Older Poly-Treated Patients Affected with Dementia.

Polypharmacy is an important issue in older patients affected by dementia because they are very vulnerable to the side effects of drugs'. Between October 2021 and September 2022, we randomly assessed 205 old-aged outpatients. The study was carried out in a Center for Dementia in collaboration with a university center. The primary outcomes were: (1) deprescribing inappropriate drugs through the Beers and STOPP&START criteria; (2) assessing duplicate drugs and the risk of iatrogenic damage due to drug-drug and drug-disease interactions. Overall, 69 men and 136 women (mean age 82.7 ± 7.4 years) were assessed. Of these, 91 patients were home care patients and 114 were outpatient. The average number of the drugs used in the sample was 9.4 drugs per patient; after the first visit and the consequent deprescribing process, the average dropped to 8.7 drugs per patient (p = 0.04). Overall, 74 potentially inappropriate drugs were used (36.1%). Of these, long half-life benzodiazepines (8.8%), non-steroidal anti-inflammatory drugs (3.4%), tricyclic antidepressants (3.4%), first-generation antihistamines (1.4%), anticholinergics (11.7%), antiplatelet drugs (i.e., ticlopidine) (1.4%), prokinetics in chronic use (1.4%), digoxin (>0.125 mg/day) (1.4%), antiarrhythmics (i.e., amiodarone) (0.97%), and α-blockers (1.9%) were included. The so-called "duplicate" drugs were overall 26 (12.7%). In total, ten potentially dangerous prescriptions were found for possible interactions (4.8%). We underline the importance of checking all the drugs taken periodically and discontinuing drugs with the lowest benefit-to-harm ratio and the lowest probability of adverse reactions due to withdrawal. Computer tools and adequately trained teams (doctors, nurses, and pharmacists) could identify, treat, and prevent possible drug interactions.