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Layered Ruddlesden-Popper (RP) neodymium nickelate oxide, Nd 2 NiO 4+δ , is considered a potential cathode material in solid oxide fuel cells. In this study, the equilibrium properties of NNO were investigated by using quasi-equilibrium oxygen release to contract the isothermal equilibrium diagram "lg pO 2 – (4+δ) – T". Furthermore, the kinetic properties of NNO were studied by oxygen partial pressure relaxation to determine the equilibrium oxygen exchange rate (R 0), chemical diffusion coefficient in oxide (D chem), and surface exchange rate constant (k chem). The Brønsted-Evans-Polanyi-type linear free energy relationship was shown to exist between the standard Gibbs energy of the reaction and the activation energy of the reaction rate constant. [ABSTRACT FROM AUTHOR]

Advancements in synthetic organic chemistry are closely related to understanding substrate and catalyst reactivities through detailed mechanistic studies. Traditional mechanistic investigations are labor‐intensive and rely on experimental kinetic, thermodynamic, and spectroscopic data. Linear free energy relationships (LFERs), exemplified by Hammett relationships, have long facilitated reactivity prediction despite their inherent limitations when using experimental constants or incorporating comprehensive experimental data. Data‐driven modeling, which integrates cheminformatics with machine learning, offers powerful tools for predicting and interpreting mechanisms and effectively handling complex reactivities through multiparameter strategies. This review explores selected examples of data‐driven strategies for investigating organic reaction mechanisms. It highlights the evolution and application of computational descriptors for mechanistic inference. [ABSTRACT FROM AUTHOR]

In this work, the magnetic and thermodynamic properties of dilute magnetic semiconductor quantum dots of cylindrical geometry are investigated. The eigenvalue of the quantum system we are considering is obtained by solving the one-electron Schrödinger equation within the framework of the effective mass approach. Then, taking into account the energy spectrum, expressions for thermodynamic quantities and magnetic susceptibility are obtained. The behavior of these expressions depending on temperature is studied using the parameters B , x , R 0 and L 0 . Based on the results obtained, it is established that the average energy, free energy, heat capacity, entropy and magnetic susceptibility at low temperatures depend on the parameter x . Also at low temperatures, when x = 0 , the average energy and free energy exhibit a linear relationship. With increasing temperature, this dependence becomes nonlinear. For x ≠ 0 , the dependence of the average energy and free energy on temperature is a rapidly increasing nonlinear function. In addition, when x ≠ 0 , magnetic susceptibility reaches a maximum at low temperatures. The peak height increases with x and disappears when x = 0 . The peak of magnetic susceptibility decreases as the magnetic field increases when x ≠ 0 and shifts toward higher temperatures. The specific heat forms a Schottky peak at low temperatures and asymptotically approaches C v = 3 k B at high temperatures. [ABSTRACT FROM AUTHOR]

The presence of bound water in clay has a significant impact on the physical and chemical properties of clay, particularly its strength, permeability, and creep behavior. In this paper, the bound water in clay has been studied from the perspective of water potential. Initially, the adsorption isotherms of powders and consolidated samples for Na- and Ca-bentonite and illite were measured, and the bound water content was determined by subtracting the capillary water in the isotherms, with the capillary water being calculated by mercury intrusion porosimetry tests. The results indicated that bound water is independent of the void ratio and pore structure of clay, which is consistent with previous studies. Then, metadynamics was conducted to determine the adsorption free energy landscapes of the three clays, and the lowest suctions of the three clay minerals were determined to be −1.7 , −5.4 , and −2.1 GPa , respectively. Finally, through a comparison of the simulations and experiments in this study and in the literature, three important conclusions were drawn. Firstly, the lowest water potential for montmorillonite exhibits a linear relationship with the hydration free energy of exchangeable cations. Secondly, the critical water potential for tightly bound water is determined as the first inflection point in the relationship between water potential and water content, and the critical value of montmorillonite is found to be correlated to the valence of exchangeable cations. Lastly, the boundary between loosely bound water and capillary water is determined as the starting point of capillary water formation. Overall, this research highlights the importance of considering water potential as a key factor in understanding the behavior of bound water in clay. [ABSTRACT FROM AUTHOR]

The high reactivity of 2‐methylene‐1,2‐dihydropyridines also known as 2‐methylpyridinium derived N‐heterocyclic olefins (2‐pyNHOs) has been recognized in organic synthesis, yet a quantification of their nucleophilicity is lacking. Herein we used stopped‐flow photometry to determine the nucleophilicity of a series of 2‐pyNHOs from the kinetics of their reactions with quinone methides and benzhydrylium ions as reference electrophiles in four organic solvents at 20 °C. The kinetic data was evaluated by using the Mayr‐Patz equation, lg k(20 °C)=sN(N+E), which gave nucleophilicity parameters N (and sN). With N in the range of 19.4–21.2 (in DMSO), 2‐pyNHOs exceed the reactivity of classical enamines, such as pyrrolidino‐cyclopent‐1‐ene. The addition of 2‐pyNHOs to quinone methides resulted in the formation of zwitterionic adducts with pyridinium and phenolate moieties. Subsequent tautomerization yielded entirely neutral pyridine‐2(1H)‐ylidene‐phenol species in several cases. Formation of the zwitterionic adducts from 2‐pyNHOs and neutral electrophiles was almost equally fast in the polar solvents acetonitrile and DMSO, but proceeded one to two orders of magnitude slower in the less polar solvents dichloromethane or THF. [ABSTRACT FROM AUTHOR]

Legacy brominated flame retardants, including polybrominated diphenyl ethers (PBDEs), have been classified as persistent organic pollutants and replaced with novel brominated flame retardants (NBFRs). The octanol–water partition coefficients (log KOW) of NBFRs have been computationally estimated, but the log KOW values provided by these methods can differ by 1 to 3 orders of magnitude. Given the importance of this parameter in fate and toxicity models, we indirectly measured the log KOW values of eight NBFRs by their capacity factor (k′) on a reversed‐phase high‐performance liquid chromatography (HPLC) C18 column by isocratic elution and compared these measured values with those estimated by nine computational models. Log KOW values were obtained for the NBFRs 1,2‐bis(2,4,6‐tribromophenoxy) ethane, pentabromobenzene, pentabromoethylbenzene, pentabromotoluene, 2‐ethylhexyl 2,3,4,5‐tetrabromobenzoate, allyl 2,4,6‐tribromophenylether, 2,3‐dibromopropyl‐2,4,6‐tribromophenyl ether, and bis(2‐ethylhexyl) tetrabromophthalate. A training set of phthalates, polychlorinated biphenyls, PBDEs, and halogenated benzenes were chosen to obtain the log k′–log KOW calibration for the NBFRs. The computational models KowWIN, XLogP3, EAS‐E Suite, COSMOtherm, DirectML, and Abraham polyparameter linear free energy relationships all predicted the log KOW values of the calibration compounds to within 1 order of magnitude without significant bias. The median of these models predicted log KOW values for the calibration compounds that were close to those known in the literature with root mean square error (RMSE) = 0.224 and for the NBFRs that were close to those measured by HPLC (RMSE = 0.334). Environ Toxicol Chem 2024;43:2105–2114. © 2024 SETAC [ABSTRACT FROM AUTHOR]

Steric manipulation is a known concept in molecular recognition but there is currently no linear free energy relationship correlating sterics to the stability of receptor‐anion complexes nor to the reactivity of the bound anion. By analogy to Tolman cone angles in cation coordination chemistry, we explore how to define and correlate cone angles of organo‐trifluoroborates (R−BF3−) to the affinities observed for cyanostar‐anion binding. We extend the analogy to a rare investigation of the anion's reactivity and how it changes upon binding. The substituent on the anion is used to define the cone angle, θ. A series of 10 anions were studied including versions with ethynyl, ethylene, and ethyl substituents to tune steric bulk across the sp, sp2 and sp3 hybridized α‐carbons bearing 0, 1 and 2 hydrogen atoms. A linear relationship between affinity and cone angle is observed for anions bearing substituents larger than the −BF3− headgroup. This correlation predicted affinities of two new anions to within ±5 %. We explored how complexation affects the reactivity of fluoride exchange. The yield of fluoride transfer from R−BF3− to Lewis acid triphenylborane is correlated with cone angle. We predict that other rigid macrocycles, like commercially available bambusuril, could follow these trends. [ABSTRACT FROM AUTHOR]

Porous carbons have potential to facilitate energy‐efficient separation of CO2 from post‐combustion flue gas. However, the complicated interplay between chemical and textural properties has prevented a comprehensive understanding of selective CO2 adsorption. This study demonstrates how dual cation activation of carbons serves as a synthetic platform to help modulate porosity independent of nitrogen content. For samples derived from nitrogen‐poor precursors, surface areas deviated significantly (2200–4500 m2 g−1) at a constant total nitrogen content (2.3 ± 0.3 at %). Surface area changed less for samples derived from nitrogen‐rich precursors (400–675 m2 g−1 at 23.1 ± 0.1 at % N). Rigorous structure‐function and thermodynamic analysis of these carbons not only helped to uncover the nature of the different adsorption sites, but also established a fundamental linear free energy exchange relationship. This coupled with material property correlations informed the properties that facilitated selective capture of CO2. Critically, for these physisorptive carbons, selectivity is almost entirely a function of relative porosity and chemical adsorbent‐adsorbate interactions play a negligible role. [ABSTRACT FROM AUTHOR]

Transition-metal-catalyzed nitrene transfer reactions are typically performed in organic solvents under inert and anhydrous conditions due to the involved air and water-sensitive nature of reactive intermediates. Overall, this study provides insights into the iron-based ([FeII(PBI)3](CF3SO3)2 (1), where PBI = 2-(2-pyridyl)benzimidazole), catalytic and stoichiometric aziridination of styrenes using PhINTs ([(N-tosylimino)iodo]benzene), highlighting the importance of reaction conditions including the effects of the solvent, co-ligands (para-substituted pyridines), and substrate substituents on the product yields, selectivity, and reaction kinetics. The aziridination reactions with 1/PhINTs showed higher conversion than epoxidation with 1/PhIO (iodosobenzene). However, the reaction with PhINTs was less selective and yielded more products, including styrene oxide, benzaldehyde, and 2-phenyl-1-tosylaziridine. Therefore, the main aim of this study was to investigate the potential role of water in the formation of oxygen-containing by-products during radical-type nitrene transfer catalysis. During the catalytic tests, a lower yield was obtained in a protic solvent (trifluoroethanol) than in acetonitrile. In the case of the catalytic oxidation of para-substituted styrenes containing electron-donating groups, higher yield, TON, and TOF were achieved than those with electron-withdrawing groups. Pseudo-first-order kinetics were observed for the stoichiometric oxidation, and the second-order rate constants (k2 = 7.16 × 10−3 M−1 s−1 in MeCN, 2.58 × 10−3 M−1 s−1 in CF3CH2OH) of the reaction were determined. The linear free energy relationships between the relative reaction rates (logkrel) and the total substituent effect (TE, 4R-PhCHCH2) parameters with slopes of 1.48 (MeCN) and 1.89 (CF3CH2OH) suggest that the stoichiometric aziridination of styrenes can be described through the formation of a radical intermediate in the rate-determining step. Styrene oxide formation during aqueous styrene aziridination most likely results from oxygen atom transfer via in situ iron oxo/oxyl radical complexes, which are formed through the hydrolysis of [FeIII(N•Ts)] under experimental conditions. [ABSTRACT FROM AUTHOR]

In this study, the application of linear free energy relationships (LFER) to log K aH + data in water at 25°C of deprotonation of protonated fused ring systems like benzimidazolium cations is carried out. With a good comparison of the sites of substituents with reference to a functional group in the benzene ring and the imidazolium ring, an excellent Hammett correlation is observed for the deprotonation of (log K aH + ) of protonated fused ring systems like benzimidazolium cations. The three substituents OH, MeO, and Me at position 4 in benzimidazole satisfy the correlation with σI values. A positive Hammet ρ value of 1.93 indicates that electron-withdrawing substituents facilitate the deprotonation. Under the same conditions, a Taft ρ* value of 1.11 is obtained for the deprotonation of 2-substituted benzimidazolium cations. The available log K aH + data in 5% aqueous ethanol at 30° C of 2-methyl benzimidazolium cations and 2-(hydroxyethyl) benzimidazolium cations also follow Hammett correlation. The lower Hammett ρ value of 0.89 for 2-(hydroxyethyl) benzimidazolium cation series than that of 1.78 for 2-methyl benzimidazolium cation series is explained in terms of strong intramolecular hydrogen bonding in 2-(hydroxyethyl) benzimidazolium cations, which resists easy deprotonation. Deprotonation of 1-substituted benzimidazolium cations does not follow the Hammett relationship, for which possible explanations are given. [ABSTRACT FROM AUTHOR]

[Display omitted] • The surface modification can significantly raise the limiting potential with −1.24 V (Ti 2 NF 2) to −0.21 V (Ti 2 BSe 2). • hybridization of the σ 2 p and π* 2 p with Ti 3 d orbitals leads to the evident splitting and downshifting of the σ and π* orbitals. • The work function plays a crucial role to predict the NRR performance by the Gibbs free energy change of the rate-determining step, which can be regulated through the surface termination of MXenes. The electrochemical conversion of nitrogen to ammonia provides an encouraging method to substitute the traditional Haber-Bosch process, owing to its high efficiency and mild reaction conditions. The search for high-performance catalysts and comprehension of catalytic mechanisms remains significant challenges. Herein, we conduct a systematic theoretical calculation of the NRR performance and mechanism of 24 Ti 2 XT 2 (X = B, C, N; T = F, Cl, Br, I, O, S, Se, Te) MXenes with a T -vacancy to explore the influence of surface functional terminations and non-metallic center elements. Our findings demonstrate that surface functionalization significantly reduces the limiting potential by altering the rate-determining step. This change ranges from −1.24 V (Ti 2 NF 2) to −0.21 V (Ti 2 BSe 2), signifying the remarkable efficacy of modification of the surrounding environment of the exposed transition metal active center in promoting electrocatalytic performance. Detailed investigation of the charge density difference and orbital interaction reveals that the different NRR performance originates from the surface termination and non-metallic atoms regulate the electronic properties of the active Ti atoms. We also introduce the free energy change of *NNH 2 (Δ G *NNH2) as a descriptor to predict the performance of NRR, which exhibits satisfactory linear relationship with free energy change of different intermediates and displays favourable volcano plot with limiting potential. Moreover, we highlight the pivotal role of work function in tuning the energy barrier of the rate-determining step, which can be regulated through the surface modification of MXenes. Our study not only offers a comprehensive understanding of the crucial impact of surface modification on the catalytic activities of defective MXenes, but also provides a rational perspective for designing efficient NRR catalysts. [ABSTRACT FROM AUTHOR]

The interactions between ether naphthotube and a series of dication guests in organic solution were investigated. It was found that ether naphthotube formed stable host‐guest complexes selectively with these guests in a 1 : 1 stoichiometric ratio with association constants ranging from 102 to 106 M−1, which were confirmed by 1H‐NMR spectra and ITC experiments. The host‐guest interactions are driven by enthalpy change as the entropic factors are unfavorable. Positive correlations between ΔH and ΔS have been observed in the host‐guest complexes. Furthermore, the para‐substitution of the guests can significantly affect the binding affinities through a combination of field/inductive and resonance effects by following a linear free energy relationship. Based on the host‐guest complexes composed of ether naphthotube and organic cations, two interlocked [2]rotaxanes were prepared by cationization reaction and Huisgen cycloaddition between the cations and the stopper components. The ether naphthotube‐based host‐guest complexes are useful for creating sophisticated interlocked molecules. [ABSTRACT FROM AUTHOR]

This study describes the development and evaluation of six new models for predicting physical–chemical (PC) properties that are highly relevant for chemical hazard, exposure, and risk estimation: solubility (in water SW and octanol SO), vapor pressure (VP), and the octanol–water (KOW), octanol–air (KOA), and air–water (KAW) partition ratios. The models are implemented in the Iterative Fragment Selection Quantitative Structure–Activity Relationship (IFSQSAR) python package, Version 1.1.0. These models are implemented as Poly-Parameter Linear Free Energy Relationship (PPLFER) equations which combine experimentally calibrated system parameters and solute descriptors predicted with QSPRs. Two other ancillary models have been developed and implemented, a QSPR for Molar Volume (MV) and a classifier for the physical state of chemicals at room temperature. The IFSQSAR methods for characterizing applicability domain (AD) and calculating uncertainty estimates expressed as 95% prediction intervals (PI) for predicted properties are described and tested on 9,000 measured partition ratios and 4,000 VP and SW values. The measured data are external to IFSQSAR training and validation datasets and are used to assess the predictivity of the models for "novel chemicals" in an unbiased manner. The 95% PI intervals calculated from validation datasets for partition ratios needed to be scaled by a factor of 1.25 to capture 95% of the external data. Predictions for VP and SW are more uncertain, primarily due to the challenges in differentiating their physical state (i.e., liquids or solids) at room temperature. The prediction accuracy of the models for log KOW, log KAW and log KOA of novel, data-poor chemicals is estimated to be in the range of 0.7 to 1.4 root mean squared error of prediction (RMSEP), with RMSEP in the range 1.7–1.8 for log VP and log SW. Scientific contribution New partitioning models integrate empirical PPLFER equations and QSARs, allowing for seamless integration of experimental data and model predictions. This work tests the real predictivity of the models for novel chemicals which are not in the model training or external validation datasets. [ABSTRACT FROM AUTHOR]

The use of experimental parameters to quantify solvent properties, for example in linear free energy relationships, is well established and several scales of solvent acidity, basicity and polarity/polarizability have been developed. The success of this approach raises questions of which molecular properties contribute to particular solvent parameters and whether these contributions are found in all parameters representing a particular solvent property. In the present study, Catalan's hydrogen bond basicity and acidity parameters, SB and SA, and Gutmann's acceptor number, AN, a measure of a solvent's Lewis acidity, are correlated with molecular properties derived from computational chemistry. The results are compared with the results of similar correlations with Kamlet and Taft's β and α Solvent Scales, Gutmann's donor number DN) and Abraham's B and A solute scales. The results show that measures of solvent basicity, SB, β and DN all correlate strongly with the partial charge on the most negative atom in the solvent molecule and the energy of the donor orbital and, in all cases, the parameter values for hydrogen-bonded solvents are anomalous. Abraham's B, a measure of solute hydrogen basicity, depends only on the partial charge on the most negative atom and there is no anomaly in the values for solutes that, in the pure state, form hydrogen-bonded liquids. Similarly, all measures of solvent acidity, SA, α and AN, and Abraham's A, a measure of solute hydrogen bond acidity, depend on the partial charge on the most positive hydrogen on the molecule. [ABSTRACT FROM AUTHOR]

The prevalence of chirality, or, handedness in biological world is a fundamental phenomenon and a characteristic hallmark of life. Thus, understanding the origin of enantio-selection, i.e., the sense and magnitude of asymmetric induction, has been a long-pursued goal in asymmetric catalysis. Herein, we demonstrated a polarizability-derived electronic effect that was shown to be capable of rationalizing a broad range of stereochemical observations made in the field of asymmetric catalysis. This effect provided a consistent enantio-control model for the prediction of major enantiomers formed in a ruthenium-catalyzed asymmetric transfer hydrogenations of ketones. Direct and quantitative linear free energy relationships between substrates' local polarizabilities and observed enantio-selectivity were also revealed in three widely known asymmetric catalytic systems covering both reductions and oxidations. This broadly applicable polarizability-based electronic effect, in conjunction with conventional wisdom mainly leveraging on steric effect considerations, should aid rational design of enantio-selective processes for better production of chiral substances. Polarizability, a property that is closely related to softness in the classic theory of Hard and Soft Acids and Bases (HSAB), has been largely overlooked in connecting with enantio-selection in the past. Here, the authors show local polarizability-based electronic effects can rationalize a wide range of stereochemical outcomes in widely-known asymmetric catalytic reactions. [ABSTRACT FROM AUTHOR]

This article, published in the journal Synlett, examines the regioselectivity of metal-catalyzed aryne reactions. Arynes are reactive compounds used to synthesize valuable species, but these reactions often result in mixtures of regioisomeric products. The article discusses the regioselectivity of free arynes and the use of electronically influencing groups to induce regioselectivity. It also explores the lack of a regioselectivity model for metal-bound arynes and the potential for ligands to control regioselectivity in aryne transformations. The authors conducted experiments using different ligands and aryne precursors to determine their impact on regioselectivity, finding that factors such as ligand size, electron donation, and steric encumbrance of the aryne influence regioselectivity. The study demonstrates the potential of ligand control in inducing regioselectivity and provides insights into the factors governing metallated aryne selectivity. [Extracted from the article]

Kinetics of the reactions of colored carbanions (reference nucleophiles) with S‐(trifluoromethyl)dibenzothiophenium ions (Umemoto's reagents) and hypervalent trifluoromethyl‐substituted iodine compounds (Togni's reagents) have been determined photometrically using stopped‐flow techniques. The second‐order rate constants k2(20 °C) for the reactions of Umemoto's sulfonium ions (generation I and II) with the reference nucleophiles in DMSO follow the correlation lg k2(20 °C)=sN(N+E) and can be used to determine the electrophilicity parameters E of these trifluoromethylating reagents. It is shown that the conditions reported for the reactions of Umemoto's generation I reagents with a variety of C‐nucleophiles are in line with the electrophilicity parameter E≈−13 determined for these reagents. Though Togni's hypervalent iodine‐based trifluoromethylation reagents do not follow this linear free energy relationship, the kinetics of their reactions with carbanions indicate that they cover the same reactivity range as Umemoto's generation I and II reagents. [ABSTRACT FROM AUTHOR]

A noncovalent organocatalytic concerted addition of phenol to glycal is developed for the stereoselective and regioselective construction of biologically important phenolic 2‐deoxyglycosides, featuring wide substrate tolerance. The method relies on an anion‐bridged dual hydrogen bond interaction which is experimentally proved by Nuclear Magnetic Resonance (NMR), Ultraviolet and visible (UV–vis), and fluorescence analysis. Experimental evidence including kinetic analysis, Kinetic Isotope Effect (KIE) studies, linear free energy relationship, Hammett plot, and density functional theory (DFT) calculations is provided for a concerted mechanism where a high‐energy oxocarbenium ion is not formed. In addition, the potential utility of this method is further demonstrated by the synthesis of biologically active glycosylated flavones. The benchmarking studies demonstrate significant advances in this newly developed method compared to previous approaches. [ABSTRACT FROM AUTHOR]

Rare Earth Elements (REE) phosphates (monazite, xenotime, and rhabdophane) are critical REE-bearing minerals typically formed in hydrothermal and magmatic ore deposits. The thermodynamic properties of those REE minerals are crucial to understanding the solubility, speciation, and transport of REE complexes. However, the standard-state Gibbs free energy of formation (∆G°f) values reported for these minerals in the literature vary by up to 25 kJ mol−1. Here, we present linear free energy relationships that allow the evaluation and estimation of the ∆G°f values at 25 °C and 1 bar for the three minerals from the ionic radius (rREE3+) and the non-solvation Gibbs free energy contribution to the REE3+ aqua ion (∆G°n, REE3+): ∆G°f,monazite − 399.71 rREE3+ = 1.0059 ∆G°n,REE3+ − 2522.51; ∆G°f,xenotime − 344.08 rREE3+ = 0.9909 ∆G°n,REE3+ − 2451.53; and ∆G°f,rhabdophane − 416.17 rREE3+ = 1.0067 ∆G°n, REE3+ − 2688.86. Moreover, based on the new dataset derived for REE end-members, we re-fitted the binary Margules parameter (W) from previous theoretical calculations into linear correlations: W + 0.00204 ∆G°'n,monazite = 39.3549 ∆V + 0.0641; W + 0.00255 ∆G°'n,xenotime = 25.4885 ∆V − 0.0062. The internally consistent thermodynamic properties of these REE phosphates are incorporated into the computer program Supcrtbl, which is available online at Zhu's research website. [ABSTRACT FROM AUTHOR]

Imidazolidine‐4‐thiones (ITOs) are cyclic, secondary amines that were considered as potential prebiotic organocatalysts for light‐driven α‐alkylations of aldehydes by bromoacetonitrile (BAN). Recent studies showed that the initially supplied ITOs represent the pre‐catalyst because they undergo S‐alkylation with BAN to give 4‐(alkylthio)‐3‐imidazolines (TIMs). Given that the same reagent mix that undergoes light‐driven α‐alkylations is also effective in the dark, we synthesized ten ITO‐ or TIM‐derived enamines of aldehydes and characterized their nucleophilic reactivities by kinetic studies in acetonitrile. The experimental second‐order rate constants k2 for reactions of enamines with benzhydrylium ions (reference electrophiles) were evaluated by the Mayr‐Patz equation, lg k2(20 °C)=sN(N+E). The determined nucleophilicities N (and sN) reveal the reactivity profiles of these enamines under prebiotically relevant conditions as well as their potential for use in organocatalytic synthesis. [ABSTRACT FROM AUTHOR]

Background: Machine learning algorithms that can quickly and easily estimate skin permeability (Kp) are increasingly being used in drug delivery research. The linear free energy relationship (LFER) developed by Abraham is a practical technique for predicting Kp. The permeability coefficients and Abraham solute descriptor values for 175 organic compounds have been documented in the scientific literature. Purpose: The purpose of this project was to use a publicly available dataset to make skin permeability predictions using the random forest and XBoost regression techniques. Methods: We employed Pandas-based methods in JupyterLab to predict permeability coefficient (Kp) from solute descriptors (excess molar refraction [E], combined dipolarity/polarizability [S], overall solute hydrogen bond acidity and basicity [A and B], and the McGowan's characteristic molecular volume [V]). Results: The random forest and XG Boost regression models established statistically significant association between the descriptors and the skin permeability coefficient. [ABSTRACT FROM AUTHOR]

Environmental context: Rare earth elements (REEs) are technologically critical elements released into the environment by various anthropogenic activities, and whose ecotoxicological impacts are still largely unknown. REE binding to natural organic matter (NOM) is key to understand their fate and bioavailability in the environment. With this work, it is now possible to predict REE binding to NOM in various environments using various speciation software (ECOSAT, ORCHESTRA, Visual MINTEQ). Rationale: Understanding rare earth element (REE) speciation in different natural environments is important to evaluate their environmental risks because different chemical species of an element may have different bioavailability and toxicity. REEs have a great affinity for particulate and dissolved organic matter, particularly fulvic and humic acids (HAs). Thus, the use of humic ion binding models may help to understand and predict the behaviour and speciation of these species in surface waters, groundwaters and soils. Methodology: In this work, we used previously published experimental datasets to parameterise the NICA–Donnan model for REEs binding with HAs, using the model optimisation tool PEST-ORCHESTRA. We propose using linear free energy relationships (LFERs) to constrain the number of parameters to optimise. Results: We determined a coherent NICA–Donnan parameter set for the whole REEs series being compatible with available generic NICA–Donnan parameters for other metals. The impact of pH, ionic strength and REE/HA ratio as well as the presence of competitors (Fe3+, Al3+ and Cu2+) on model results is analysed. Discussion: We consolidate confidence in our derived NICA–Donnan parameters for REEs by comparing them with the Irving–Rossotti LFER. We also show the general applicability of this relationship to predict and constrain metal-binding parameters for the NICA–Donnan model. We discuss observed shortcomings and provide suggestions for potential improvement of NICA–Donnan modelling. Environmental context. Rare earth elements (REEs) are technologically critical elements released into the environment by various anthropogenic activities, and whose ecotoxicological impacts are still largely unknown. REE binding to natural organic matter (NOM) is key to understand their fate and bioavailability in the environment. With this work, it is now possible to predict REE binding to NOM in various environments using various speciation software (ECOSAT, ORCHESTRA, Visual MINTEQ). This article belongs to the collection Dedication to Prof. Edward Tipping. [ABSTRACT FROM AUTHOR]

The consistency principle represents a physicochemical condition requisite for ideal protein folding. It assumes that any pair of amino acid residues in partially folded structures has an attractive short-range interaction only if the two residues are in contact within the native structure. The residue-specific equilibrium constant, K, and the residue-specific rate constant, k (forward and backward), can be determined by NMR and hydrogen-deuterium exchange studies. Linear free energy relationships (LFER) in the rate-equilibrium free energy relationship (REFER) plots (i.e., log k vs. log K) are widely seen in protein-related phenomena, but our REFER plot differs from them in that the data points are derived from one polypeptide chain under a single condition. Here, we examined the theoretical basis of the residue-based LFER. First, we derived a basic equation, ρij = ½(φi + φj), from the consistency principle, where ρij is the slope of the line segment that connects residues i and j in the REFER plot, and φi and φj are the local fractions of the native state in the transient state ensemble (TSE). Next, we showed that the general solution is the alignment of the (log K, log k) data points on a parabolic curve in the REFER plot. Importantly, unlike LFER, the quadratic free energy relationship (QFER) is compatible with the heterogeneous formation of local structures in the TSE. Residue-based LFER/QFER provides a unique insight into the TSE: A foldable polypeptide chain consists of several folding units, which are consistently coupled to undergo smooth structural changes. [ABSTRACT FROM AUTHOR]

The expansion of possible areas of use of modern gas chromatography is largely determined by the thermal stability of stationary liquid phases (SLP), which allows the separation of complex mixtures of high-boiling compounds. A way to increase the thermal stability of nonpolar and weakly polar polysiloxane SLPs is to introduce rigid fragments into the polysiloxane chain. Currently, there is an extensive set of columns with thermostable SLPs, which, in some cases, have the index "ms". However, in most cases, the nature of these phases and the methods for preparing the columns are not disclosed. In this work, using the linear free energy relationship (LFER) model, we compared the selectivity of a number of proprietary columns with in-house columns in which the siloxane–silarylene phase and the column preparation methods themselves are known. Various types of intermolecular interactions are considered within the framework of the LFER model. [ABSTRACT FROM AUTHOR]

In the present work, the dispersive surface free energy was calculated by Dorris-Gray method for 30 samples of adsorbents modified with chiral supramolecular structures of uracil, 6-methyluracil, 5-hydroxy-6-methyluracil, 5-fluorouracil, thymine, melamine, cyanuric and barbirutic acids, and perylene-3,4,9,10-tetracarboxylic dianhydride. It was shown that the homologous series of n-alkanes is better suited for measuring dispersive surface free energy than the homologous series of alcohols. It was established that the classical Dorris-Gray method does not allow obtaining well interpretable data for the objects studied. This is due to a noticeable effect that inductive interactions of a polar surface as an inductor with nonpolar alkane molecules have on the calculated values. We suggested to modify the Dorris-Gray method, making it possible to obtain data on the dispersive component of the free energy of adsorption. It was shown that the changes in dispersive surface free energy as a result of the modification correlate well with data on the structure and properties of supramolecular ensembles of the modifiers used. The results obtained can be used to predict the enantioselectivity of chiral adsorbents.

To provide a more straightforward protocol, we envisioned that a boron-catalyzed carboxylic acid enolate formation approach, previously developed by some of us, [28] would enable direct -trifluoromethylthiolation of carboxylic acids (Scheme 1c). Direct -Trifluoromethylthiolation of Carboxylic Acids Enabled by Boron Catalysis Carboxylic acid, boron catalyst, trifluoromethylthiolation, data science, drug modification, fluorine compounds Keywords: carboxylic acid; boron catalyst; trifluoromethylthiolation; data science; drug modification; fluorine compounds EN carboxylic acid boron catalyst trifluoromethylthiolation data science drug modification fluorine compounds 2210 2214 5 10/31/23 20231127 NES 231127 Graph Incorporation of fluorine atoms and fluoro-functional groups in a molecule has been essential for the development of pharmaceuticals and agrochemicals. [Extracted from the article]

With an increase in production and application of various engineering nanomaterials (ENMs), they will inevitably be released into the environment. Adsorption of various organic chemicals onto ENMs will impact on their environmental behavior and toxicology. It is unrealistic to experimentally determine adsorption equilibrium constants (K) for the vast number of organics and ENMs due to high cost in expenditure and time. Herein, appropriate molecular dynamics (MD) methods were evaluated and selected by comparing experimental K values of seven organics adsorbed onto graphene with the MD-calculated ones. Machine learning (ML) models on K of organics adsorption onto graphene and black phosphorus nanomaterials were constructed based on a benchmark data set from the MD simulations. Lasso models based on Mordred descriptors outperformed ML models built by support vector machine, random forest, k-nearest neighbor, and gradient boosting decision tree, in terms of cross-validation coefficients (Q2 > 0.90). The Lasso models also outperformed conventional poly-parameter linear free energy relationship models for predicting logK. Compared with previous models, the Lasso models considered more compounds with different functional groups and thus have broader applicability domains. This study provides a promising way to fill the data gap in logK for chemicals adsorbed onto the ENMs. [ABSTRACT FROM AUTHOR]

The possibilities and problems to predict excited‐state acidities and basicities in water with electronic structure calculations combined with a continuum solvation model are investigated for a test set of photoacids and photobases. Different error sources, like errors in the ground‐state pKa values, the excitation energies in solution for the neutral and (de‐)protonated species, basis set effects, and contributions beyond implicit solvation are investigated and their contributions to the total error in pKa∗ are discussed. Density functional theory in combination with the conductor like screening model for real solvents and an empirical linear Gibbs free energy relationship are used to predict the ground‐state pKa values. For the test set, this approach gives more accurate pKa values for the acids than for the bases. Time‐dependent density‐functional theory (TD‐DFT) and second‐order wave function methods in combination with the conductor like screening model are applied to compute excitation energies in water. Some TD‐DFT functionals fail for several species to predict correctly the order of the lowest excitations. Where experimental data for absorption maxima in water is available, the implicit solvation model leads with the applied electronic structure methods in most cases for the excitation energies in water to an overestimation for the protonated and to an underestimation for the deprotonated species. The magnitude and sign of the errors depend on the hydrogen bond donating and accepting ability of the solute. We find that for aqueous solution this results generally in an underestimation in the pKa changes from the ground to the excited state for photoacids and an overestimation for photobases. [ABSTRACT FROM AUTHOR]

Below we present the results of these investigations organized by aryl iodide structure as follows: 1) 4-Substituted aryl iodides, 2) 2- and 3-substituted aryl iodides, 3) 2-substituted 4-iodoanisole derivatives, 4) 2-substituted iodoveratrole derivatives, and 5) additional miscellaneous electron-rich aryl iodides. E SB p/2 sb values are presented for all aryl iodides and I SB p sb values (in blue in the figures) are presented only for those aryl iodides that display quasireversible electrochemistry. Keywords: hypervalent iodine; electrochemistry; linear free-energy relationships; sustainable catalysis; oxidation EN hypervalent iodine electrochemistry linear free-energy relationships sustainable catalysis oxidation 3019 3025 7 08/31/23 20230915 NES 230915 Graph Aryl iodide electrocatalysis provides a conceptual platform to combine the inherent sustainability of electrochemical oxidation with the mechanistic diversity available to hypervalent iodine-mediated transformations. [4] As a result, the application of aryl iodide electrochemistry is often limited to ex-cell applications in which anodic aryl iodide oxidation is temporally separated from substrate functionalization, which prevents undesired side reactions but obviates the potential for electrocatalysis. [Extracted from the article]

Hammond's postulate, which relates the rate of formation of an unstable intermediate to the energy of this intermediate, has widely been used to determine stabilities of carbocations. However, the rates of formation of highly stabilized carbocations R+ by ionization of R−X are only weakly or not at all correlated with their stabilities, because the corresponding activation energies are strongly affected by intrinsic barriers. In this article we will show that consideration of the rate of the reverse reaction allows one to define the range in which Hammond's postulate holds and when its predictive power fades as the role of intrinsic barriers is gaining importance. The ambiguity of the term "carbocation stability" is discussed. Kinetic data and quantum chemical calculations show that vinyl cations are not extraordinarily high energy intermediates, but that high intrinsic barriers account for their slow formation from vinyl halides and their rather slow reactions with nucleophiles. [ABSTRACT FROM AUTHOR]

This document explores the application of machine learning in supramolecular chemistry, specifically in the field of analytical chemistry. It discusses the concept of linear free energy relationships (LFERs) and their historical development, including the Brønsted equations and Hammett plots. The document introduces multivariate LFERs, which consider multiple variables to provide deeper insight into structure-reactivity relationships. It emphasizes the potential of machine learning in generating models that predict chemical observables and encourages chemists to embrace this powerful predictive tool. [Extracted from the article]

The acidity constants (pKa) of bromocresol purple in various water-dioxane mixtures were determined. The proposed approaches allow prediction of pKa values of bromocresol purple in any mixture of water-dioxane. The results were discussed in terms of the solvent characteristic. The pKa values of the investigated indicator were found to be largely dependent on the ratio of dioxane. This result is confirmed by linear correlation between mol fraction of dioxane and acidity constant due to the solvation of bromocresol purple with both water and dioxane molecules in all binary mixtures. The results showed non-linear relationship between pKa values and reciprocal relative permittivity that indicates both the electrostatic and non-electrostatic which affecting on the acidity constant. A linear solvation free energy relationship was used to study the effects of solvent and solute properties on the acidity constants in some dioxane solvent mixtures. The pKa values were correlated with the Kamlet-Taft solvatochromic parameters of mixtures from water with dioxane. It was mainly affected by non-electrostatic solute-solvent interactions. The KAT multi-parameter correlations represent significant improvements with regard to single-or dual-parameter models with highest F-static. [ABSTRACT FROM AUTHOR]

This work built a molecular‐level kinetic model for hydrocarbon catalytic cracking, incorporating the catalyst acidity as the parameter to estimate reaction rates. The n‐decane and 1‐hexene co‐conversion catalytic cracking process was chosen as the studying case. The molecular reaction network was automatically generated using a computer‐aided algorithm. A modified linear free energy relationship was proposed to estimate the activation energy in a complex reaction system. The kinetic parameters were initially regressed from the experimental data under several reaction conditions. On this basis, the product composition was evaluated for three catalytic cracking catalysts with different Si/Al. The Bronsted acid and Lewis acid as the key catalyst properties were correlated with kinetic parameters. The built model can calculate the product distribution, gasoline composition, and molecular distribution at different reaction conditions for different catalysts. This sensitive study shows that it will facilitate the model‐based optimization of catalysts and reaction conditions according to product demands. [ABSTRACT FROM AUTHOR]

The roles of substituent and solvent effects in promoting the 4π electrocyclization of N‐alkenylnitrones to give azetidine nitrones have been investigated by experimental examination of relative rates, activation energies, and linear free energy relationships. These transformations are synthetically important because they favor the formation of a strained heterocyclic ring with imbedded functionality and stereochemical information for versatile derivatization. Mechanistic investigations, including Hammett studies, solvent‐dependent Eyring studies, and solvent isotope effects, provide insight into the steric and electronic factors that control these electrocyclizations and identify trends that can be used to advance this approach towards the rapid synthesis of complex azetidines. [ABSTRACT FROM AUTHOR]

Large-scale drug screening is currently the basis for the identification of new chemical entities. This is a rather laborious approach, because a large number of compounds must be tested to cover the chemical space in an unbiased fashion. However, the structures of targetable proteins have become increasingly available. Thus, a new era has arguably been ushered in with the advent of methods, which allow for structure-based docking campaigns (i.e., virtual screens). Solute carriers (SLCs) are among the most promising drug targets. This claim is substantiated by the fact that a large fraction of the 400 solute carrier genes is associated with human diseases. The ability to dock large ligand libraries into selected structures of solute carriers has set the stage for rational drug design. In the present study, we show that these structure-based approaches can be refined by taking into account how solute carriers operate. We specifically address the feasibility of targeting solute carriers with allosteric modulators, because their actions differ fundamentally from those of ligands, which bind to the substrate binding site. For the pertinent analysis we used transition state theory in conjunction with the linear free energy relationship (LFER). These provide the theoretical framework to understand how allosteric modulators affect solute carrier function. [ABSTRACT FROM AUTHOR]

Cyclopropanes that carry an electron-accepting group react as electrophiles in polar, ring-opening reactions. Analogous reactions at cyclopropanes with additional C2 substituents allow one to access difunctionalized products. Consequently, functionalized cyclopropanes are frequently used building blocks in organic synthesis. The polarization of the C1–C2 bond in 1-acceptor-2-donor-substituted cyclopropanes not only favorably enhances reactivity toward nucleophiles but also directs the nucleophilic attack toward the already substituted C2 position. Monitoring the kinetics of non-catalytic ring-opening reactions with a series of thiophenolates and other strong nucleophiles, such as azide ions, in DMSO provided the inherent SN2 reactivity of electrophilic cyclopropanes. The experimentally determined second-order rate constants k2 for cyclopropane ring-opening reactions were then compared to those of related Michael additions. Interestingly, cyclopropanes with aryl substituents at the C2 position reacted faster than their unsubstituted analogues. Variation of the electronic properties of the aryl groups at C2 gave rise to parabolic Hammett relationships. [ABSTRACT FROM AUTHOR]

Analytic expressions for the three- and four-particle correlation functions of the hard disk fluid in terms of geometric functionals have been derived using the combined geometric/thermodynamic idea of Boublik [Fluid Phase Equilib. 316, 1 (2012)]. To assess the approximate result, extensive Monte Carlo simulations were performed to obtain the triplet correlation function, g3, over a wide range of densities. We then focussed on the rolling contact configurations that are required in the second-order thermodynamic perturbation theory of patchy colloid models. The analytic approximation is shown to perform very well, and the simulation data have therefore been parametrized using Boublik's functional form for their subsequent use. [ABSTRACT FROM AUTHOR]

Large-scale drug screening is currently the basis for the identification of new chemical entities. This is a rather laborious approach, because a large number of compounds must be tested to cover the chemical space in an unbiased fashion. However, the structures of targetable proteins have become increasingly available. Thus, a new era has arguably been ushered in with the advent of methods, which allow for structure-based docking campaigns (i.e., virtual screens). Solute carriers (SLCs) are among the most promising drug targets. This claim is substantiated by the fact that a large fraction of the 400 solute carrier genes is associated with human diseases. The ability to dock large ligand libraries into selected structures of solute carriers has set the stage for rational drug design. In the present study, we show that these structure-based approaches can be refined by taking into account how solute carriers operate. We specifically address the feasibility of targeting solute carriers with allosteric modulators, because their actions differ fundamentally from those of ligands, which bind to the substrate binding site. For the pertinent analysis we used transition state theory in conjunction with the linear free energy relationship (LFER). These provide the theoretical framework to understand how allosteric modulators affect solute carrier function.

Predicting the logarithm of hexadecane/air partition coefficient (L) for organic compounds is crucial for understanding the environmental behavior and fate of organic compounds and developing prediction models with polyparameter linear free energy relationships. Herein, two quantitative structure activity relationship (QSAR) models were developed with 1272 L values for the organic compounds by using multiple linear regression (MLR) and support vector machine (SVM) algorithms. On the basis of the OECD principles, the goodness of fit, robustness and predictive ability for the developed models were evaluated. The SVM model was first developed, and the predictive capability for the SVM model is slightly better than that for the MLR model. The applicability domain (AD) of these two models has been extended to include more kinds of emerging pollutants, i.e., oraganosilicon compounds. The developed QSAR models can be used for predicting L values of various organic compounds. The van der Waals interactions between the organic compound and the hexadecane have a significant effect on the L value of the compound. These in silico models developed in current study can provide an alternative to experimental method for high-throughput obtaining L values of organic compounds. Ø Six molecular descriptors were utilized for establishing MLR and SVM models. Ø For predictive ability, the SVM model performs slightly better than the MLR one. Ø The ADs for MLR and SVM models cover more kinds of organosilicon compounds. Ø The van der Waals interactions can influence the L value significantly. [Display omitted] [ABSTRACT FROM AUTHOR]

Diazocyclopentadiene reacts with benzhydrylium ions (Ar2 CH+) to give 2,5-dibenzhydryl-substituted diazocyclopentadienes. The kinetics have been determined photometrically in dichloromethane under pseudo-first-order conditions using diazocyclopentadiene in excess. Plots of the second-order rate constants (log k 2) versus the electrophilicity parameters E of the benzhydrylium ions gave the nucleo-philicity parameter N = 4.84 and susceptibility s N = 1.06 for diazo-cyclopentadiene according to the correlation log k (20 °C) = s N (E + N). Diazocyclopentadiene thus has a similar nucleophilic reactivity as pyrrole. Previously reported electrophilic substitutions of diazocyclopentadiene are rationalized by these parameters and new reaction possibilities are predicted. [ABSTRACT FROM AUTHOR]

Transition metal intermediates bearing M−X σ‐bonds are ubiquitous in metal‐mediated C−X bond transformations. Thermodynamic knowledge of M−X bond cleavage is crucial to explore relevant reactions; but little was accumulated till present due to lack of suitable determination methods. We here report the first systematic study of the Pd−X bond homolysis dissociation free energies [BDFE(Pd−X)] of representative [(tmeda)Pd(4‐F−C6H4)X] (tmeda=N,N,N′,N′‐tetramethylethylenediamine, X=OR or NHAr) in DMSO on the basis of reliable measurement of their bond heterolysis energies (ΔGhet(Pd−X)). Despite ΔGhet(Pd−O)s of palladium‐phenoxides are generally found about 8 kcal/mol smaller than ΔGhet(Pd−N)s of palladium‐amidos, their BDFE(Pd−X)s are observed comparable. The structure‐property relationship was investigated to disclose an enhancement effect of electron‐withdrawing groups on BDFE(Pd−X)s. Linear free energy relationship analysis revealed that Pd−X bonds are more sensitive than X−H bonds to structural variation. The energetic propensity of reductive elimination from arylpalladium complexes was evaluated by combinatorial use of BDFE(Pd−X)s and BDFE(C−X)s, indicating an overall thermodynamic bias to C−N bond formation. [ABSTRACT FROM AUTHOR]

Series of photochromic 1,2‐bis(thienyl)ethenes possessing perfluorocyclopentene backbones, either hydrogen or methyl groups at the β‐positions of the thiophenes, and a variety of substituents in their α'‐positions were prepared, which cover the range from electron‐donating to electron‐withdrawing (Me, −CH2OH, −OTBS, −TMS, −Br, 1,3‐dioxan‐2‐yl, pyridin‐4‐yl, −CH2OH, −COOH). As a linear free energy relationship the spectroscopic Hammett equation gives fair to excellent fits to the excitation energy of the absorption maxima of the ring‐opened as well as the ring‐closed forms of the BTEs, when Hammett substituent constants σp were replaced by Brown's modified substituent constants σp+ and σp−. Vice versa, hitherto unknown Hammett‐Brown substituent constants can be estimated from the UV spectra. Furthermore, we compared the experimentally measured absorption maxima with values which we calculated by three different methods (DFT STEOM‐DLPNO‐CCSD/def2‐TZVPP, TD‐DFT ωB97X‐D3/6‐31G*, TD‐DFT ωB97X‐D3/6‐311++G**). [ABSTRACT FROM AUTHOR]

Linear Free Energy Relationships (LFER) logKj = a⋅logKi between the stability constants (logK) of the Mn+L complexes of ith and jth metal ions Mn+ (Ca2+, Cd2+, Co2+, Cu2+, Fe2+, La3+, Mg2+, Mn2+, Ni2+, Pb2+, Th4+, VO2+, Y3+, Zn2+) with diverse organic ligands (L) in water were analyzed. From these 432 LFER it follows that each metal ion can be described by one parameter - thermodynamic ionic radius r, and the stability constants of two metal ions Mi and Mj with a ligand L are related by the simple relationship logKj = (ri/rj)logKi. Predictive performance of this relationship was tested on 228 metal ion pairs which were not used for the radii estimations, and the number of ligands varied from 20 to 221 for these metal ion pairs. Root mean squared error RMSE and squared determination coefficient R d e t 2 of the logK predictions vary from 0.50 to 2.0 for 186 test sets and from 0.849 to 0.500 for 218 test sets, respectively. [ABSTRACT FROM AUTHOR]

Methods for extrapolating measured in vitro intrinsic clearance to a whole‐body biotransformation rate constant (kB) have been developed to support modeled bioaccumulation assessments for fish. The inclusion of extrapolated kB values into existing bioaccumulation models improves the prediction of chemical bioconcentration factors (BCFs), but there remains a tendency for these methods to overestimate BCFs relative to measured values. Therefore, a need exists to evaluate the extrapolation procedure to assess potential sources of error in predicted kB values. We examined how three different approaches (empirically based, composition based, and polyparameter linear free energy relationships [ppLFERs]) used to predict chemical partitioning in vitro (liver S9 system; KS9W), in blood (KBW), and in whole fish tissues (KFW) impact the prediction of a chemical's hepatic clearance binding term (fU) and apparent volume of distribution (VD), both of which factor into the calculation of kB and the BCF. Each approach yielded different KS9W, KBW, and KFW values, but resulted in fU values that were of similar magnitude and remained relatively constant at log octanol–water partition ratios (KOW) greater than 4. This is because KBW and KS9W values predicted by any given approach exhibit a similar dependence on log KOW (i.e., regression slope), which results in a cancelation of "errors" when fU is calculated. In contrast, differences in KBW values predicted by the three approaches translate to differences in VD, and by extension kB and the BCF, which become most apparent at log KOW greater than 6. There is a need to collect KBW and VD data for hydrophobic chemicals in fish that can be used to evaluate and improve existing partitioning prediction approaches in extrapolation models for fish. Environ Toxicol Chem 2023;42:33–45. © 2022 SETAC [ABSTRACT FROM AUTHOR]

The octanol–air partition ratio (KOA) describes the partitioning of a chemical between air and octanol and is often used to approximate other partitioning phenomena in environmental chemistry (e.g., blood–air, atmospheric particulate matter–air, polyurethane foam-air). Such partitioning processes often occur at environmental temperatures other than 25 °C. Enthalpies Δ H OA ∘ or internal energies Δ U OA ∘ of phase transfer are used to express the temperature dependence of the KOA. Existing poly-parameter linear free energy relationships (ppLFERs) for predicting Δ H OA ∘ were developed using a relatively small dataset. In this work we utilize a recently developed comprehensive KOA database to create and curate a Δ U OA ∘ dataset containing 195 chemicals and use this dataset in the development of new predictive equations. Using the QSAR development platform QSARINS we evaluate the use of Abraham descriptors, other molecular descriptors, and the log10KOA at 25 °C as variables in different multilinear regression equations for Δ U OA ∘ . The Δ U OA ∘ of neutral organic chemicals can be reliably predicted using only the log10KOA (RMSEEXT = 6.86 kJ·mol−1, R adj 2 = 0.94), only the solute's hydrogen acidity A and the logarithm of the hexadecane–air partition ratio L (RMSEEXT = 7.23 kJ·mol−1, R adj 2 = 0.93), or A and log10KOA (RMSEEXT = 6.76 kJ·mol−1, R adj 2 = 0.95). [ABSTRACT FROM AUTHOR]

Determining the contaminants reduction rate by dissolved ferrous iron (Fe(II) aq) bound to iron oxides is curial for evaluating the abiotic attenuation of contaminants in aquifers. However, few studies have assessed the contaminants reduction rate controlled by thermodynamic parameters in heterogeneous systems with different iron oxides. In this study, a linear free energy relationship (LFER) was established between the nitrobenzene reduction rate and the thermodynamic driving force (reduction potential (E H) and pH) in Fe(II) aq -goethite-hematite co-existing systems. Results showed that the reduction rate of nitrobenzene correlated with the E H of the heterogeneous system. The standard reduction potential (E H 0 mix) of the mixed iron oxides could be obtained by a proportionate linear combination of the single iron oxide system E H 0. Based on this, the E H of the heterogeneous systems could be calculated theoretically by combining E H 0 mix and the Nernst equation. Furthermore, a parallel LFER with the slope of 1 was established to associate the nitrobenzene reduction rate with E H and pH. The intercept term was related to the adsorption capacity of different iron oxides towards Fe(II) aq. The Fe(II) aq saturation adsorption capacity of hematite was 1.5 times higher than that of goethite. After normalizing the nitrobenzene reduction rate to the Fe(II) aq saturation adsorption capacity, the maximum difference in intercept terms was reduced from 37% to 15%. These findings would provide an important and feasible methodological support for the quantitative evaluation of abiotic attenuation of contaminants in groundwater. • Parallel LFERs correlate the reduction rate of contaminants with E H and pH. • E H of different iron oxides-Fe(II) aq systems can be theoretically calculated. • Intercept of LFERs depend on the interaction between iron oxides and Fe(II) aq. [ABSTRACT FROM AUTHOR]

Machine learning (ML) including Abraham descriptors from polyparameter linear free energy relationships (pp-LFERs) has been a popular method for the adsorption coefficient (K d) prediction. However, Abraham descriptors from pp-LFERs are concentration-dependent and the significance of these descriptors can change over different adsorbate concentrations. Ignoring concentration effects on the adsorption process and K d prediction will hinder the understanding of interactions among solutes, solvents and adsorbents at different equilibrium concentration (C e) ranges. Therefore, our study first systematically investigated the concentration effects on micropollutant adsorption to carbon-based adsorbents using ML with Abraham descriptors. Concentration-selection approach, as a new data-splitting approach, divided the whole dataset according to the different C e ranges. This concentration-selection approach performed better than the data-splitting approach used in previous studies. After the ML models were built in different C e subsets, Shapley values were calculated to quantify input descriptor contributions. The results indicated specific surface area (BET) was the only critical factor when C e was in the highest range. The importance of Abraham descriptors increased gradually when C e decreased. Total pore volume (V t) was a far less important feature than BET for K d prediction. Critical factors identified at different C e ranges for K d prediction provide a guidance for novel carbon-based adsorbent design. [Display omitted] • Concentration selection outcompeted group selection during training model. • Specific surface area was the only important factor when adsorbate concentration was high. • Importance of Abraham descriptors increased when adsorbate concentration decreased. • Total pore volume alone was a far less important feature than specific surface area for adsorption coefficient prediction. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ultra-high temp sterilization reduces spoilage in coconut milk with minimal aroma loss. • Coconut milk aroma analyzed using Electronic nose, gas chromatography, and spectrometry. • Odor attributes and volatiles correlation analyzed via chromatography and sensory tasting. • Substance changes in heat-treated coconut milk revealed via relative odor activity value. Coconut milk products are susceptible to bacterial damage, necessitating sterilization methods that often compromise nutrient and aroma integrity. This study investigates the effects of different thermal sterilisation methods on coconut milk aroma using headspace gas chromatography-ion mobility spectrometry (HS-GC-IMS) and headspace solid-phase microextraction gas chromatography-mass spectrometry (HS-SPME-GC-MS). We assessed the impact of pasteurisation (PAS, 70 °C, 25 min), high-temperature sterilisation (HTS, 121.1 °C, 15 min), and ultra-high temperature sterilisation (UHT, 130 °C, 5 s) through clustered heat maps and correlation analyses. Significant differences were observed (p < 0.05), with 37 and 52 substances detected by HS-GC-IMS and HS-SPME-GC-MS, respectively, identifying 12 key aroma compounds. UHT treatment primarily reduced 8 acids, maintaining a compositional structure and sensory profile similar to raw coconut milk. PAS and HTS treatments decreased the sensory intensity of overall coconut milk aroma, creamy, and floral notes, correlating with the presence of 2-heptanol, nonanal, 4-methylvaleric acid, and 2-tridecanone. These methods increased cooked notes, associated with 5-methyl-3-heptanone, 3-butyn-1-ol, hydroxyacetone, and acetoin. Rancidity was linked to acids such as isobutyric acid, isovaleric acid, and heptanoic acid, with high temperatures effectively reducing these compounds. Prolonged temperature changes in PAS and HTS accelerated lipid oxidative degradation and the Maillard reaction, involving free fatty acids in the formation of alcohols, aldehydes, esters, and lactones. These findings provide a theoretical basis for studying coconut milk flavour deterioration. [ABSTRACT FROM AUTHOR]