Kinetic Experiments Research Articles

Valorizing copper-contaminated manure into biochar for tetracycline adsorption: Dynamics and interactions of tetracycline adsorption and copper leaching.

Valorizing copper-contaminated manure into biochar for tetracycline adsorption: Dynamics and interactions of tetracycline adsorption and copper leaching.

Interaction of native and aggregated albumin with DMPC bilayers.

Interaction of native and aggregated albumin with DMPC bilayers.

Novel C-4 sulfenylated pyrazoles as α-amylase inhibitors: Insights from in silico and in vitro studies.

Novel C-4 sulfenylated pyrazoles as α-amylase inhibitors: Insights from in silico and in vitro studies.

Bacterial nanocellulose/Cu-Fe-CN composite for the uptake of Cs(I) from aqueous solutions.

Bacterial nanocellulose/Cu-Fe-CN composite for the uptake of Cs(I) from aqueous solutions.

Copper doped carbon dots for selective determination of regulated aniline additives and safe hair dyeing.

Copper doped carbon dots for selective determination of regulated aniline additives and safe hair dyeing.

Mixed surfactants for stabilizing and controlling water transport in double emulsions.

Double emulsions, comprising an aqueous droplet enclosed within an oil shell, hold great potential as versatile microcompartments for a variety of applications. However, their widespread utility is often limited by inherent instability and uncontrolled water transport. In this study, we use droplet microfluidics to prepare double emulsions with uniform thin oil shells stabilized by mixed surfactant systems. By combining monomeric and polymeric surfactants, we demonstrate that polymeric surfactants enhance stability by preventing oil shell drainage, while monomeric surfactants substantially increase water transport above a critical concentration, albeit reducing the emulsion lifespan. Swelling kinetics experiments, coupled with small-angle neutron scattering analysis, reveal that interface-controlled water transport occurs via mixed reverse micelle solubilization. This study provides valuable insights into designing double emulsions with optimized surfactant compositions, enabling enhanced stability and tunable water transport, with potential applications across food, cosmetics, and drug delivery systems.

Kinetics of Hydrogenation of Dimethyl Oxalate to Methyl Glycolate on an Activated Carbon-Supported Copper Catalyst

A catalyst with the active component Cu loaded onto the carrier activated carbon was prepared, and metal Ca was introduced into the catalyst to modify it. This catalyst was used in the hydrogenation reaction of dimethyl oxalate, and the reaction kinetics was studied. The kinetic experiments were carried out in a fixed bed reactor with a reaction temperature varying from 483 K to 513 K, reaction pressure varying from 1.5 Mpa to 2.5 Mpa, and the weight hourly space velocity of dimethyl oxalate varying from 0.435 h−1 to 0.726 h−1. Eight possible dynamic models were proposed, the optimal model was selected, and the parameters of the optimal model were calculated using MATLAB. The results showed that dimethyl oxalate adsorbed on the active site by dissociation adsorption, and the dissociation adsorption of ester was the rate-controlling step. The parameters of the model were consistent with thermodynamics and statistical analysis, further proving that the model has good forecasting performance.

Enantioselective Nickel‐Catalyzed Hydrogenation of α‐Alkylidene Succinimides Enabled by Weak Noncovalent Interactions

The development of asymmetric hydrogenation catalysts based on Earth‐abundant metals presents a sustainable alternative to efficient but resource‐limited rare‐metal systems. However, these catalysts often suffer from low catalytic activity. In this study, through a combination of density functional theory (DFT) calculations and kinetic experiments, we uncovered a positive correlation between catalyst‐substrate weak noncovalent interactions and catalytic efficiency in the enantioselective nickel‐catalyzed hydrogenation of α‐alkylidene succinimides with different N‐protecting groups. The tert‐butyl (tBu) substituent emerged as the optimal choice, significantly enhancing reactivity. This approach enabled the hydrogenation of a wide range of substrates with excellent yields (up to 99%) and enantioselectivities (up to 99% ee), achieving a substrate/catalyst (S/C) ratio of 4000—twice the efficiency of rare‐metal catalysts (S/C ≤ 2000) for similar transformations. Energy decomposition analysis (EDA) of the enantiomers revealed that the high stereoselectivity is promoted by stabilizing weak noncovalent interactions in the R‐configured transition state.

Enantioselective Nickel-Catalyzed Hydrogenation of α-Alkylidene Succinimides Enabled by Weak Noncovalent Interactions.

The development of asymmetric hydrogenation catalysts based on Earth-abundant metals presents a sustainable alternative to efficient but resource-limited rare-metal systems. However, these catalysts often suffer from low catalytic activity. In this study, through a combination of density functional theory (DFT) calculations and kinetic experiments, we uncovered a positive correlation between catalyst-substrate weak noncovalent interactions and catalytic efficiency in the enantioselective nickel-catalyzed hydrogenation of α-alkylidene succinimides with different N-protecting groups. The tert-butyl (tBu) substituent emerged as the optimal choice, significantly enhancing reactivity. This approach enabled the hydrogenation of a wide range of substrates with excellent yields (up to 99%) and enantioselectivities (up to 99%ee), achieving a substrate/catalyst (S/C) ratio of 4000-twice the efficiency of rare-metal catalysts (S/C≤2000) for similar transformations. Energy decomposition analysis (EDA) of the enantiomers revealed that the high stereoselectivity is promoted by stabilizing weak noncovalent interactions in the R-configured transition state.

Manganese Complex-Catalyzed (De)hydrogenative Cyclization toward the Selective Synthesis of 2-Substituted and 2,3-Disubstituted 4-Quinolones.

Herein, we describe bifunctional NNO-Mn(I)-catalyzed switchable synthesis of 3-benzyl-2-phenylquinolin-4(1H)-one and 2-phenylquinolin-4(1H)-one and their derivatives via (de)hydrogenative annulation of a host of alcohols with diverse amino acetophenones. To expand the versatility of our catalytic protocol, we conducted postsynthetic modification featuring bioactive compounds and synthesized 4-quinolones with antibiotic properties. Control and kinetic experiments were carried out to validate the mechanistic analysis, demonstrating that C-alkylation is preferred over N-alkylation in the synthesis of both heterocycles.

Reactivity study of 3,3-dimethylbutanal and 3,3-dimethylbutanone: kinetics, reaction products, mechanisms, and atmospheric implications

Abstract. 3,3-dimethylbutanal (33DMbutanal, (CH3)3CCH2C(O)H) and 3,3-dimethylbutanone (33DMbutanone, (CH3)3CC(O)CH3) are carbonyl compounds that could play a key role in tropospheric chemistry. To better understand the effects of carbonyl compounds in the atmosphere, a kinetic and mechanistic study was conducted on the degradation of 33DMbutanal and 33DMbutanone with atmospheric oxidants (Cl atoms, OH and NO3 radicals). The kinetic experiments were performed at 710 ± 30 Torr and at room temperature (298 ± 5 K) using a relative method and Fourier transform infrared (FTIR) spectroscopy to monitor the reactions. The rate coefficients (k in units of cm3molec.-1s-1) obtained were kCl+33DMbutanal = (1.27 ± 0.08) × 10−10, kCl+33DMbutanone = (4.22 ± 0.27) × 10−11, and kOH+33DMbutanone = (1.26 ± 0.05) × 10−12. The reaction products were also determined using FTIR spectroscopy and gas chromatography–mass spectrometry (GC-MS). The main products observed were carbonyl compounds, including acetone, formaldehyde, and 2,2-dimethylpropanal. In the presence of NO, nitrated compounds were also formed, and, at high NO2 concentrations, peroxyacetyl nitrate (PAN) and peroxy-3,3-dimethylbutyryl nitrate were identified. Other unquantified compounds were multifunctional organic compounds and organic acid of low volatility. Both 33DMbutanal and 33DMbutanone degrade rapidly near emission sources with minimal impact on radiative forcing. However, they may contribute to tropospheric ozone (O3), with a photochemical ozone creation potential (POCP) range of 15–69, and secondary organic aerosol (SOA) formation, potentially worsening air quality and contributing to photochemical smog.

Evaluating the Origins of Aerobic Oxidation Catalysiswith TAM-3, a MOF with Accessible Co(II) Sites and Large Pores

Metal-organic frameworks(MOFs) are attractive platforms that mergeconcepts of homogeneous and heterogeneous catalysis. Catalyst designand optimization are enabled by an array of synthetic methods thatoffer independent control over the local chemical structure of lattice-embeddedmetal ions (i.e., ligand identity and geometry) and the long-rangematerials properties (i.e., porosity). Establishing the origin ofcatalytic activity in MOF-promoted reactions remains a significantchallenge: The relative rates of catalyst turnover and substrate diffusiondictate the extent to which interstitial sites are accessible andoperational in catalysis. To minimize the contributions of surfacesites in catalysis, materials with large pore dimensions are oftensought, however, the impact of pore expansion on the origins of catalyticactivity is similarly challenging to establish. Here, we describeTAM-3, a Co­(II) based MOF with accessible metal sites supported bya facially coordinating tris-tetrazole ligand set.TAM-3 features large channel-like pores (17 × 23 Å) andpromotes aerobic C–H oxidation and olefin epoxidation. Usinga set of simple kinetics experiments, based on the analysis of kineticisotope effects and olefin oxidation diastereoselectivities, we demonstratethat despite the large pores, interstitial metal ions do not significantlycontribute to the observed substrate oxidation. This study highlightsthe importance of conducting kinetic experiments to assess the originof apparent catalytic activity with MOFs and the challenge of harnessingreactive oxidants with microporous catalyst materials.

Nanoparticles for improving biogas production and effluent biofertilizer

The impact of nanoparticles (NP) mixtures (Fe + Ni + Co, Fe + Ni, Fe + Co, and Ni + Co) on the anaerobic digestion (AD) of cow manure was examined through kinetic modelling (Modified Gompertz, Logistic, and First-order kinetic) and experimental observations. The NPs mixture significantly enhanced biogas production rate and yield potential. The variation between predicted and actual biogas yields was smaller with the Modified Gompertz model (1.37% to 5.30%) and First-order kinetic model (0.04% to 3.83%) compared to the Logistic model (1.99% to 7.04%). Additionally, digestates containing NPs showed strong fertility properties (5.16% to 5.36%). The combined use of kinetic models and experiments offers an effective way to quantify the influence of NPs mixture on AD performance, aiding in industrial application.

Microwave‐assisted Ag‐IL for extraction separation of α‐olefins: Mechanistic insights and process intensification

Abstract The actual applications of extraction methods for α‐olefins separation are limited by their long time and high energy consumption. Hence, this study employs microwave technology to intensify the extraction process using Ag‐based ionic liquid (Ag‐IL), where the influence of microwave irradiation and the mechanism of microwave‐assisted ionic liquid extraction (MAILE) are investigated, along with a comprehensive techno‐economic analysis of process feasibility. The results of COSMO‐RS and DFT simulations demonstrate the dominant role of π‐complexation in identifying Ag‐IL with high selectivity, indicating the possible enhancement caused by microwave irradiation. The subsequent kinetic experiments show that compared with conventional routes, the MAILE accelerated the extraction process by approximately 89.72%. As a result, the total annual cost of unit product of the overall process is reduced by 6.43% according to techno‐economic analysis by Aspen Plus, indicating that MAILE is a cost‐effective, scalable, and sustainable approach to α‐olefin separation, offering process efficiency and environmental sustainability.

Degradation of aqueous 3-tertbutyl-4-hydroxyanisole with co-existing propyl gallate by zero-valent iron activated persulfate: Kinetic study and products identification

Degradation of aqueous 3-tertbutyl-4-hydroxyanisole with co-existing propyl gallate by zero-valent iron activated persulfate: Kinetic study and products identification

Synthesis of hyperbranched polyamidoamine-modified chitosan aerogel and its efficient adsorption of Cr(VI) from aqueous solution.

Synthesis of hyperbranched polyamidoamine-modified chitosan aerogel and its efficient adsorption of Cr(VI) from aqueous solution.

1H-NMR and molecular networking-guided dereplication of phloroglucinol meroterpenoids from Cleistocalyx operculatus buds as neuraminidase inhibitors.

1H-NMR and molecular networking-guided dereplication of phloroglucinol meroterpenoids from Cleistocalyx operculatus buds as neuraminidase inhibitors.

Immobilization and release behaviors of uranium mediated by the redox processes between manganese oxides and dissolved organic matter: Effects of pH and goethite.

Immobilization and release behaviors of uranium mediated by the redox processes between manganese oxides and dissolved organic matter: Effects of pH and goethite.

Regiodivergent and Enantioselective Hydroboration of Dienol Ethers.

Transition metal-catalyzed asymmetric hydroboration of alkenes is one of the most straightforward methods for the synthesis of chiral organoboron compounds and has been well-established. While significant progress has been made in the catalytic enantioselective hydroboration of simple dienes, the development of regiodivergent and enantioselective hydroboration of more challenging substrates such as heteroatom-substituted or trisubstituted dienes remains limited. Here we disclose a cobalt-catalyzed regiodivergent and enantioselective hydroboration of dienol ethers using a commercially available Co(acac)2 catalyst and chiral ligands. The reaction exhibits good functional group compatibility and broad substrate scope, selectively affording 1,2-, 4,1-, 1,4-, and 4,3-hydroboration products in good yields and high regio- and enantioselectivities (up to >99%). Mechanistic studies including deuterium-labeling, kinetic, and UV-Vis experiments suggest the involvement of Co-H species as active catalysts in the reactions. The powerful conversion capabilities of the products are demonstrated by various downstream transformations and the efficient preparation and late-stage elaboration of bioactive compounds.

Multistage Activation Barriers in the Chiral Metallosupramolecular Polymerization of Alkynylplatinum(II) Complexes.

In the process of supramolecular polymerization, kinetic barriers are pivotal in dictating the polymerization pathway and dynamics, thereby intricately modulating both the binding rate and the mechanism involved in the formation of supramolecular polymers. Here, the multistage activation barriers associated with dynamic pathway complexity are reported in the helical metallosupramolecular polymerization of chiral terpyridine-based alkynylplatinum(II) complexes (R-L1-Pt and S-L1-Pt) in a DMSO and H2O mixture (6:4 v/v). The kinetic experiments reveal the presence of a kinetically favored aggregate (Agg-I) that initially forms and subsequently converts to another, more stable kinetic aggregate (Agg-II), accompanied by helicity inversion. Finally, the kinetic aggregate transforms into a thermodynamically favored form (Agg-III) through an additional metal-to-metal ligand charge transfer (MMLCT). The average rate constants (k1 and k2) in nucleation and elongation steps, as well as the activation barriers associated with both kinetic and thermodynamic aggregates, are determined using the Finke-Watzky (F-W) two-step model and the Eyring-type plot method, respectively, confirming that the process follows Eyring behavior. Notably, the activation barrier of the formation of Agg-III is the highest observed. Additionally, the activation barrier is modulated by the addition of Agg-III seeds.