Reaction Kinetics Research Articles

Ion- and surface-sensitive interactions during oxygen evolution reaction in alkaline media

Abstract Clean and sustainable energy has turned towards electrochemical water splitting as a viable solution in minimizing carbon emissions. Electrolysis of water converts electrical energy to chemical energy, through the production of hydrogen and oxygen gases, which can be harnessed for potential applications without contributing to greenhouse emissions. While this energy storage process shows great potential, its efficiency is hindered by the sluggish kinetics of the oxygen evolution reaction (OER). As a result, its widespread application in green electrolytic technologies is limited hence investigations on improving OER kinetics are of utmost importance. Recent research breakthroughs indicate that alkali metal cations are more than passive observers. They play complex roles in the electric double layer (EDL), which positively influences the OER kinetics. The presence of numerous ions and their combinations presents a challenge of complexity. This study aims to delve into the impact of alkali metal cations on OER activity due to the variance in their hydration energies. Specific investigations focusing on different alkali metal cations in solution, such as Li+, Na+, and K+, was conducted on RuO2 to gain a deeper understanding of how these ions interact with both reactants and intermediate species in the reaction kinetics. Traditional electrochemical tests, including cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and accelerated degradation test (ADT) measurements were employed to elucidate critical aspects such as surface activation, electric double layer interactions, catalytic activity and stability, ohmic resistance, and mass and charge transport.

Reaction kinetics and mechanism of UVC-LED265–285nm and UVC-LED265–285nm/hydrogen peroxide toward foodborne pathogenic Listeria monocytogenes cells and its chromosomally encoded virulent hly genes

To investigate the principle-based inactivation kinetics and mechanisms of the foodborne pathogen Listeria monocytogenes (Lm), along with its representative virulence gene (hly) encoded in both intracellular and extracellular genomic DNA, we applied disinfection treatments using UVC-LED265–285nm and UVC-LED265–285nm combined with hydrogen peroxide (10 mg/L). These treatments were conducted under controlled model reaction matrices (phosphate-buffered solutions at pH 6.2 and 7.9) and/or actual agricultural water, depending on filtration pre-treatment. Comprehensive analytical methods, such as plate count, flow cytometry, and quantitative real-time PCR, were adopted for the qualitative/quantitative determination of bacterial or gene inactivation parameters. According to the experimentally determined fluence-based first-order rate constants (kUVC-LED and kUVC-LED/H2O2), the k value of Lm viability and hly genes was 1.14–2.19 cm2/mJ and 2.18 × 10−2–2.42 × 10−1 cm2/mJ, respectively. Damage to the longer amplicon or the extracellular form of the hly gene was higher than that to the shorter amplicon or the intracellular form by a factor of 2∼10 fold. Increasing pH in reaction matrices were marginally affected to the rates of inactivation kinetics. Dose-dependent inactivation levels tested in agriculture water matrices were comparable with the kinetics from the PB solutions of both UVC-LED265–285nm and UVC-LED265–285nm/hydrogen peroxide owing to OH radical scavenging by the water matrix components. These results will be valuable for optimizing UVC-LED and UVC-LED-based advanced oxidation process disinfection systems, specifically tailored to the unique challenges of bacterial or gene inactivation in the (waste)water at food processing and agricultural sectors.

Theoretical studies into the degradation mechanisms and kinetics of gemfibrozil mediated by hydroxyl and sulfate radicals in the aqueous phase and ecotoxicity evaluation

Gemfibrozil (GEM), an acidic pharmaceutical used to reduce plasma triglycerides and total cholesterol levels, persists in conventional wastewater treatment processes. However, understanding its degradation mechanism and kinetics through advanced oxidation processes (AOPs) remains unexplored. Therefore, this study employed density functional theory (DFT) at the M06-2X/6-311++G(3df,2p) //M06-2X/6-311G(d,p) level to theoretically investigate the oxidation of GEM by hydroxyl and sulfate radicals in aqueous environments. Mechanistic pathways, reaction kinetics, and ecotoxicological assessments were conducted. Two distinct mechanisms involving addition and hydrogen abstraction were delineated. The overall rate constants, accounting for diffusion-limited effects, were determined as 1.84 × 109 M−1 s−1 and 7.73 × 109 M−1 s−1 at 298 K for •OH and SO4•−-initiated reactions, respectively. Analysis revealed that hydrogen abstraction at the carboxyl group predominated, while favorable addition occurred at the carbon atom positioned at the 3rd position of the benzene ring. The calculated half-life of GEM initiated by •OH and SO4•− was approximately 377 and 97 s with their concentration of 10−12 mol/L at 298 K. Ecotoxicity assessment via quantitative structure-activity relationship (QSAR) indicated a certain degree of danger posed by GEM and its degradation by-products to aquatic organisms, albeit exhibiting lower toxicity compared to GEM itself.

Chemical Kinetics and Thermal Properties of Ablator Pyrolysis Products During Atmospheric Entry

Legacy and modern-day ablation codes typically assume equilibrium pyrolysis gas chemistry. Yet, experimental data suggest that speciation from resin decomposition is far from equilibrium. A thermal and chemical kinetic study was performed on pyrolysis gas advection through a porous char, using the Theoretical Ablative Composite for Open Testing (TACOT) as a demonstrator material. The finite-element tool SIERRA/Aria simulated the ablation of TACOT under various conditions. Temperature and phenolic decomposition rates generated from Aria were applied as inputs to a simulated network of perfectly stirred reactors (PSRs) in the chemical solver Cantera. A high-fidelity combustion mechanism computed the gas composition and thermal properties of the advecting pyrolyzate. The results indicate that pyrolysis gases do not rapidly achieve chemical equilibrium while traveling through the simulated material. Instead, a highly chemically reactive zone exists in the ablator between 1400 and 2500 K, wherein the modeled pyrolysis gases transition from a chemically frozen state to chemical equilibrium. These finite-rate results demonstrate a significant departure in computed pyrolysis gas properties from those derived from equilibrium solvers. Under the same conditions, finite-rate-derived gas is estimated to provide up to 50% less heat absorption than equilibrium-derived gas. This discrepancy suggests that nonequilibrium pyrolysis gas chemistry could substantially impact ablator material response models.

Copper/Cobalt based metal phosphide composites as positive material for supercapacitors

The excellent conductivity and fast redox kinetics of transition metal phosphides (TMPs) have made them a suitable electrode material for energy storage in the field of supercapacitors (SCs). In this paper, coral-like Cu3P/CoP heterostructures have been obtained by a simple solid-phase grinding and subsequent phosphating method. Importantly, the Cu3P/CoP heterostructure can provide sufficient charge to further accelerate the Faraday kinetics of the redox reaction due to its ability to generate an internal electric field, thus improving its electrochemical performance. Through density-functional theory (DFT) computations, it is demonstrated that the heterostructures of Cu3P/CoP enhances the metal-like conductivity of the composite, exhibiting more electron-occupied states around the Fermi energy level and improves the charge-transfer efficiency of the heterostructure. The results show that the Cu3P/CoP-1 composite with a 1:1 Cu/Co molar ratio has the best electrochemical performance. At 1 A·g−1, it exhibits an excellent specific capacitance of 804.3F·g−1, and when the current density is increased to 10 A·g−1, it retains its capacitance for 92.8 % of 10,000 cycles. Furthermore, with a power density of 806.23 W·kg−1, an asymmetric supercapacitor (ASC) built using Cu3P/CoP-1 as the cathode may produce an energy density of 37.40 Wh·kg−1. The reasonable design of heterostructures of bimetallic TMPs in this research offers a workable plan for exploring electrode materials with excellent capacitive properties.

Three-dimensional porous structured cobalt- and nitrogen-doped carbon nanotube electrocatalyst derived from cobalt-based zeolitic imidazolate framework nanoleaves for high performance zinc-air battery

The development of efficient and cost-effective electrocatalysts to overcome the intrinsic sluggish kinetics of the oxygen reduction reaction (ORR) in zinc-air batteries is crucial. In this study, we introduce a strategy that integrates a template-assisted synthesis with subsequent thermal treatment to fabricate an active and stable cobalt-based nitrogen-doped carbon electrocatalyst, denoted as Co-N-CNT. The strategy adjusts the disordered architecture of the zeolitic imidazolate framework (ZIF) through the synergistic effect of bimetallic species, restricted the growth of zeolitic imidazolate framework nanoleaves (ZIF-L) using salt templates, and directed the transformation from a two-dimensional blade-like morphology to a three-dimensional multi-tiered composite structure. Notably, the Co-N-CNT-800 sample, synthesized at an optimized pyrolysis temperature of 800 °C, exhibits a half-wave potential of 0.89 V and demonstrates stability with sustained cycling over 21 h, which is comparable to the performance of commercial Pt/C electrocatalysts. Moreover, when employed as the cathode in zinc-air batteries, Co-N-CNT-800 not only surpasses Pt/C in terms of power density but also exhibits long-term charge/discharge stability. This findings offer a viable pathway for the design of active and cost-effective ORR electrocatalysts, holding promise for applications in the electrochemical energy storage and conversion systems.

MOF-on-MOF-derived FeCo@NC OER&ORR bifunctional electrocatalysts for zinc-air batteries

Zinc-air batteries, as one of the emerging areas of interest in the quest for sustainable energy solutions, are hampered by the intrinsically sluggish kinetics of the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and still suffer from the issues of low energy density. Herein, we report a MOF-on-MOF-derived electrocatalyst, FeCo@NC-II, designed to efficiently catalyze both ORR (Ehalf = 0.907 V) and OER (Ej=10 = 1.551 V) within alkaline environments, surpassing esteemed noble metal benchmarks (Pt/C and RuO2). Systematically characterizations and density functional theory (DFT) calculations reveal that the synergistic effect of iron and cobalt bimetallic and the optimized distribution of nitrogen configuration improved the charge distribution of the catalysts, which in turn optimized the adsorption / desorption of oxygenated intermediates accelerating the reaction kinetics. While the unique leaf-like core–shell morphology and excellent pore structure of the FeCo@NC-II catalyst caused the improvement of mass transfer efficiency, electrical conductivity and stability. The core and shell of the precursor constructed through the MOF-on-MOF strategy achieved the effect of 1 + 1 > 2 in mutual cooperation. Further application to zinc-air batteries (ZABs) yielded remarkable power density (212.4 mW/cm2), long cycle (more than 150 h) stability and superior energy density (∼1060 Wh/kg Zn). This work provides a methodology and an idea for the design, synthesis and optimization of advanced bifunctional electrocatalysts.

Designing nanoporous Pd catalyst with dual enhancement of thermodynamics and kinetics for formic acid oxidation reaction

Conventional strategies for developing highly efficient electrocatalysts involve enhancing thermodynamics to minimize overpotential and improving kinetics to maximize reaction current. However, current research on Pd-based catalysts for formic acid oxidation reaction (FAOR) mainly focuses on accelerating its kinetics to increase the peak current. This study proposes a catalyst design that can simultaneously improve the kinetics and thermodynamics of FAOR. Specifically, the home-made catalyst (NPG-Pt1-Pd1) is obtained by sequentially depositing monolayer Pt and Pd shells on the surface of nanoporous gold (NPG) substrate. Compared with commercial Pd/C, this electrocatalyst exhibits a noticeable negative shift in onset potential (~100mV) and a significantly improved peak current (~6 times). Experimental data and theoretical calculations demonstrate that NPG-Pt1-Pd1 exhibits a comparatively suitable adsorption energy for small molecules, not only reducing the overpotential but also accelerating the reaction rate of FAOR. Moreover, when applied in direct formic acid fuel cells (DFAFC), the NPG-Pt1-Pd1 anode with an exceptionally low Pd loading of 8.5μgcm-2, achieves a remarkable power density of 141mWcm-2. The power efficiency of Pd is 230 times that of Pd/C (1mgcm-2, 73mWcm-2). Therefore, this work provides a new methodology for developing efficient Pd-based FAOR electrocatalysts.

Promising Catalyst for Chlorosilane Dismutation

Currently, the most common method of silane synthesis for electronics and photovoltaics is trichlorosilane dismutation. Therefore, an experimental study of the kinetics of the dismutation reaction of chlorosilanes is of scientific and practical interest. A catalyst has been proposed that allows the dismutation reaction to be carried out in a wide range of temperatures and pressures. Both kinetic and thermodynamic data on the dependence of the rate of the dismutation reactions of trichlorosilane, dichlorosilane, and monochlorosilane on pressure were experimentally obtained. In addition, the dependence of saturated vapor pressure on temperature for monochlorosilane and dichlorosilane were also experimentally determined. Using the example of TCS, it was experimentally established that increasing the pressure to six atmospheres makes it possible to increase the specific productivity of the reactor by at least an order of magnitude due to the acceleration of the chemical reaction and the increase in the molar concentration of chlorosilanes in the vapor mixture. Consequently, it becomes possible to multiply the reactor’s load on the substance and, accordingly, the performance of the chlorosilane dismutation apparatus in general.

Bulk-phase and surface dual-defective engineering enabled Ti-based nanotubes photoanode for highly efficient photoelectrochemical water splitting

Photoelectrochemical (PEC) water splitting employing Ti-based nanostructures represents a promising strategy for achieving solar-to-hydrogen (STH) conversion. Nevertheless, the process is largely hindered by intrinsic sluggish kinetics of the oxygen evolution reaction (OER) process. In this work, we fabricate a high-efficiency Vo/TiNbO photoanode by anodizing the specifically designed Ti–Nb alloys followed by one-step electrochemical reduction. It's worth noting that bulk-phase and surface dual-defective engineering involved in Ti-based nanotubes could be utilized as effective micro-reaction platform for augmented PEC water splitting. Microstructure analysis demonstrates that bulk-phase doping and surface oxygen defects lead to a negative shift of valence-conductive band edges, which increases electrical conductivity and optical absorption. An impressive STH conversion efficiency of the co-doped system could reach 1.12 %, which is 4.6 times of pristine system. Density functional theory (DFT) calculation further confirms that the synergistic dual-defective effects play a vital role in boosting OER process. With the optimization of coordination electron configuration, determining rate step (DRS) energy barrier and adsorption energy of key intermediates decrease. We hope that the rational amalgamation of bulk-phase elements doping with surface oxygen defects introduced in this work may provide insights into developing high-performance nanostructured photoanodes for driving solar water splitting.

Development and experimental validation of a thermo-metallurgical-mechanical model of the Laser Metal Deposition (LMD) process

The current paper presents the development and experimental validation of a thermo-metallurgical-mechanical model for a multi-pass Laser Metal Deposition (LMD) process, with the objective of accurately predicting the resultant constituent phases and residual stresses. The thermal model is calibrated using temperature readings and is shown to accurately capture the transient temperature field and extent of the fusion zone associated with the multi-pass LMD process. The metallurgical model incorporates the kinetics of ongoing solid-state phase transformations (SSPTs) and tempering reactions. The predictions are validated via hardness measurements, demonstrating a very good agreement with the predictions. The developed mechanical model predicts the residual stress field, which is validated using X-ray diffraction measurements, and the comparison also shows a very good agreement between the predictions and measurements. The validated numerical model is then used to explore alternative LMD strategies showing that the choice of deposition strategy can significantly impact resultant constituent phases and residual stresses.

FeMnO3/CNT as a synergistic bifunctional electrocatalyst for oxygen reduction and oxygen evolution reactions in alkaline medium

The development of highly effective and low-cost electrocatalysts for energy conversion and storage devices is triggered by the sluggish kinetics of oxygen reduction and evolution reactions. Perovskite-based oxides are identified as potential ORR and OER electrocatalysts in an alkaline medium. Thus, the present study discusses the synthesis and characterization of FeMnO3/CNT as a bifunctional catalyst with a low potential gap of 0.89 V. The FeMnO3/CNT composite was synthesized by the solution combustion method and characterized using spectroscopic and electron microscopic techniques. The increase in the ID/IG ratio obtained from the Raman spectra of the FeMnO3/CNT composite with respect to bare CNT indicates the functionalization of CNT. The ORR and OER characteristics of the FeMnO3/CNT composite were analyzed with rotating ring disc electrode and rotating disc electrode measurements. The LSV curve of the FeMnO3/CNT composite synthesized with 0.3g of CNT show better ORR and OER activity. The ORR activity measurements of the composite done in 0.1 M KOH electrolyte show a good onset potential of 0.95 V vs. RHE and a half-wave potential of 0.74 V. The HPRR studies show that the ORR reaction mechanism follows a 2e− + 2e− reduction pathway. The OER measurements in an alkaline medium show an onset potential of 1.63 V vs. RHE with a Tafel slope of 115.3 mV dec−1. Also, this work gives an insight into the fundamental understanding of the synergy between the perovskite and CNT, leading to an enhanced ORR and OER catalytic activity. In addition, the material exhibits good stability for ORR and OER stability studies.

Durable and dense zwitterionic polymer brushes initiated from Surface-Segregated cyclic initiator via atom transfer radical polymerization

Immobilization of initiators on a polymer surface for surface-initiated polymerization has primarily been achieved via covalent bonds. However, this approach is subject to limitations, such as the requirement for additional processing steps and different customized methods tailored to the specific characteristics of each polymer. In this study, initiator immobilization was achieved by surface segregation, a phenomenon observed in polymer blends wherein one component spontaneously enriches the surface, thereby enabling the modification of surface properties. Specifically, we designed cyclic oligomers containing an atom transfer radical polymerization (ATRP) initiator. The enhanced performance of surface segregation mediated by the cyclic topology was evaluated, along with the surface-initiated polymerization initiated by the surface-segregated oligomer. The kinetics of the ATRP reaction for the cyclic initiators were investigated, and the zwitterion polymer brush density was also calculated. The robustness of the brushes was evaluated through leaching tests, which revealed no notable alterations before and after the assessments. The antifouling effect of the brushes was confirmed through protein adsorption, platelet adhesion, bacterial attachment, and whole-blood circulation experiments. These antifouling examinations demonstrated reduced substance attachment of zwitterionic polymer brushes. Lastly, experiment on optimizing the ATRP catalyst loading during the surface-initiated ATRP was conducted. The excellent performance of the cyclic initiators is expected to provide new insights and opportunities in the field of surface-initiated polymerization. Moreover, the formation of zwitterion brushes via cyclic initiators holds promise for versatile applications in the field of long-term utilization in biointerfaces, offering a wide range of potential uses.

Boosting Nitrate Electroreduction to Ammonia on Atomic Ru-Co Pair Sites in Hollow Spinels

Electrocatalytic nitrate reduction reaction (NO3RR) to ammonia (NH3) provides a promising way to simultaneously remove widespread nitrogen pollution and electrify NH3 manufacturing. However, developing suitable electrocatalysts to efficiently convert NO3--to-NH3 remains a great challenge because of the slow kinetics of NO3RR and competitive hydrogen evolution reaction (HER). Herein, we reported a novel method to incorporating Ru single atom into hollow Co3O4 to construct atomically dispersed Ru-Co pair sites (Ru1-Co/HCO) for efficient NO3- electroreduction to NH3, with a maximal NH3 Faradaic efficiency of ~100% and a yield rate as high as 7.02mgh-1 cm-2 (11.0mgh-1 mgcat-1). The NO3RR activity can be explained by the synergistic tandem effect of Ru1-Co pair sites, where Ru sites are responsible for activating NO3- and stabilizing the intermediates, and neighboring Co site promotes water dissociation to generate active hydrogen (*H) for accelerating intermediate hydrogenation on Ru sites, alleviating the site competition between NO3RR and HER. A Zn–NO3- battery coupled with in-situ NH3 recovery device was also assembled to achieve the co-generation of high-purity NH4Cl fertilizer and electricity. Our work paves a new way for boosting NO3RR activity via constructing dual active sites.

Leveraging doping strategies and interface engineering to enhance catalytic transformation of lithium polysulfides for high-performance lithium-sulfur batteries

The commercialization of lithium-sulfur (Li–S) batteries has faced challenges due to the shuttle effect of soluble intermediate polysulfides and the sluggish kinetics of sulfur redox reactions. In this study, a synergistic catalyst medium was developed as a high-performance sulfur cathode material for Li–S batteries. Termed A/R-TiO2@ Ni-N-MXene, this sulfur cathode material features an in-situ derived anatase–rutile homojunction of TiO2 nanoparticles on Ni-N dual-atom-doped MXene nanosheets. Using in-situ transmission electron microscopy (TEM) technique, we observed the growth process of the homojunction for the first time confirming that homojunctions facilitated charge transfer, while dual-atom doping offered abundant active sites for anchoring and converting soluble polysulfides. Theoretical calculations and experiments showed that these synergistic effects effectively mitigated the shuttle effect, leading to improved cycling performance of Li–S batteries. After 500 cycles at a 1C rate, Li–S batteries using A/R-TiO2@Ni-N-MXene as cathode materials exhibited stable and highly reversible capacity with a capacity decay of only 0.056 % per cycle. Even after 150 cycles at a 0.1C rate, a high-capacity retention rate of 62.8 % was achieved. Additionally, efficient sulfur utilization was observed, with 1280.76 mA h/g at 0.1C, 694.24 mA h/g at 1C, alongside a sulfur loading of 1.5–2 mg/cm2. The effective strategy based on homojunctions showcases promise for designing high-performance Li–S batteries.

Renewable Biomass based Jet Fuel: Aldol condensation of furfural with 3-pentanone over calcium zirconium mixed oxide catalyst

Furfural is a biomass-derived chemical that can be converted into different valuable chemicals using green processes. The current study deals with a highly efficient, robust, and selective solid catalyst for the aldol condensation of furfural and 3-pentanone to synthesize 1-furan-2-yl-2-methylpent-1-en-3-one under environmentally benign conditions. The CaZr (different molar ratios of Ca and Zr) mixed oxide (MO) catalysts along with CaO and ZrO2 catalysts were prepared by the hydrothermal technique and investigated for the current reaction. Among all, the CaZr (1:2) MO catalyst was resulted to be the best for the conversion of furfural due to its desirable basic strength with good surface area and reusability characteristics. Furfural conversion and 1-furan-2-yl-2-methylpent-1-en-3-one selectivity were found to be 94% and 98%, respectively, under optimized reaction conditions. The effect of various reaction parameters was studied carefully to reach the maximum yield of the required product. Reaction mechanism and kinetics were developed. The reaction aligns with the LHHW mechanism, and the activation energy was determined to be 10.40kcal/mol.

Dynamic in situ reconstruction of NiSe2 promoted by interfacial Ce2(CO3)2O for enhanced water oxidation

Understanding and manipulating the structural evolution of water oxidation electrocatalysts lays the foundation to finetune their catalytic activity. Herein, we present a synthesis of NiSe2-Ce2(CO3)2O heterostructure and demonstrate the efficacy of interfacial Ce2(CO3)2O in promoting the formation of catalytically active centers to improve oxygen evolution activity. In-situ Raman spectroscopy shows that incorporation of Ce2(CO3)2O into NiSe2 causes a cathodic shift of the Ni2+→Ni3+ transition potential. Operando electrochemical impedance spectroscopy reveals that strong electronic coupling at heterogeneous interface accelerates charge transfer process. Furthermore, density functional theory calculations suggest that actual catalytic active species of NiOOH transformed from NiSe2, which is coupled with Ce2(CO3)2O, can optimize electronic structure and decrease the free energy barriers toward fast oxygen evolution reaction (OER) kinetics. Consequently, the resultant NiSe2-Ce2(CO3)2O electrode exhibits remarkable electrocatalytic performance with low overpotentials (268/304 mV @ 50/100 mA cm−2) and excellent stability (50 mA cm−2 for 120 h) in the alkaline electrolyte. This work emphasizes the significance of modulating the dynamic changes in developing efficient electrocatalyst.

Candida Antarctica Lipase B Mediated Kinetic Resolution: a Sustainable Method for Chiral Synthesis of Antiproliferative β-Lactams

Biocatalysis is a valuable industrial approach in active pharmaceutical ingredient (API) manufacturing for asymmetric induction and synthesis of chiral APIs. Herein, we investigated synthesis of a panel of microtubule-destabilising antiproliferative β-lactam enantiomers employing a commercially available immobilised Candida antarctica lipase B enzyme together with methanol and MTBE. The β-lactam ring remained intact during chiral kinetic resolution reactions, plausibly due to a bulky N-1 phenyl substituent on the β-lactam ring substrate. The predominant reaction mediated by CAL-B was methanol catalysed conversion of the β-lactam 3-acetoxy substituent to a 3-hydroxyl group, with preferential methanolysis of the 3S,4S enantiomer. The unreacted substrate underwent progressive enantioenrichment to the 3R,4R enantiomer. Substitution patterns on the B ring C3 meta position of the β-lactam scaffold greatly affected the rate of reaction. Halo substituents (fluoro-, chloro- and bromo-) reduced the rate of conversion compared to unsubstituted analogues, which in turn increased enantiomeric excess (ee). Ee values up to 86% for the 3S,4S 3-hydroxyl enantiomer were achieved. A double resolution approach for unreacted substrate yielded high ee values (>99%) for the 3R,4R 3-acetoxy enantiomer. CAL-B mediated methanolysis is a more sustainable method for resolution of racemic antiproliferative β-lactams compared to a previous technique of chiral diastereomeric resolution. Yields of β-lactams obtained using CAL-B are far superior than previously described, which will facilitate progression toward pre-clinical and clinical development. Biocatalysis is a useful tool in the toolbox of the medicinal chemist.

Crystallization resolution of racemic compounds via chiral surfactant

As one of the basic attributes of nature and the universe, chirality is valuable in biology, medicine, and materials science. However, enantiomer resolution remains a long-standing challenge. Herein, a novel surfactant for resolution of racemic compound with high performance has been outlined. Firstly, we synthesized a chiral surfactant and its chiral recognition ability to L-Alanine molecules was confirmed. Subsequently, the solid–liquid equilibrium curves were used to design the resolution route. The synthesized surfactant was further utilized to intensify the crystallization process of the racemic compound, resulting in a remarkable increase of L-Alanine products’ ee values from 0 % to 99 %. Finally, quantum chemical calculations and molecular dynamics simulations were employed to uncover the stereoselectivity recognition mechanism of surfactant to L-Alanine molecules. Overall, we propose a new idea for direct crystallization resolution of racemic Alanine by chiral surfactants that differs from the “rule of reversal”, which is highly attractive for chiral resolution.

Structure and interactions of CO2 with reline (a 1:2 choline chloride – Urea mixture) according to quantum chemical calculations and molecular dynamics simulation

Quantum chemical DFT calculations [B3LYP+GD3/6-311++g(2d,2p)] of the structure and interactions in various complexes of CO2 molecule with a choline cation, a chloride anion, urea molecules, a choline chloride ion pair and a 1:2 choline chloride – urea complex were carried out. The contributions of Coulomb and van der Waals interactions were calculated. The QTAIM method was used to evaluate the strength of various bonds. A molecular dynamics simulation of CO2 molecules in reline in the NPT ensemble (1 atm, 298 K) was also carried out. The radial distribution functions of the particle centers of mass, local mole fraction functions, spatial distribution functions, and density profiles were calculated. Stronger interactions, compared to the other DES components, were observed in case of the chloride anion and the CO2 molecule according to the DFT calculations. However, in the system, stronger interactions were observed between the chloride anion and the system components, namely NHCl and OHCl hydrogen bonds. This made the chloride anion inaccessible and unable to interact with the CO2 molecule, according to the MD simulation results. Additionally, the presence of a fairly extensive surface layer containing DES and CO2 molecules was shown.