Tailoring the properties of cellulose aerogel beads was investigated in the present study by using weak organic acids as coagulants. Three different weak acids were specifically chosen, acetic acid, lactic acid and citric acid. For comparative studies, a strong acid, hydrochloric acid was examined. The production of aerogel beads by conventional dropping technique was controlled and optimized for weak acids. Aerogels were characterized by density analyses, scanning electron microscopy, nitrogen adsorption-desorption analysis, X-ray powder diffractometry and IR spectroscopy. In common, all the aerogel beads showed interconnected nanofibrillar network, high specific surface area, high pore volume, high porosity and meso- and macroporous structure. In particular, when the weakest acid (acetic acid) was used as coagulant in the regeneration bath, the lowest shrinkage was observed. As a result, the cellulose aerogel beads produced from acetic acid showed the highest values of specific surface area (423 m2·g-1) and pore volume (3.6 cm3·g-1). The porous structure can be tuned by the choice of regeneration bath having either strong acid or high concentration of weak acid. The aerogel beads were pure and showed cellulose II crystallinity. Hence this study paves an alternative path way to tailor the properties of cellulose aerogel beads.

Functional group compatibility in an amide bond cleavage reaction with hydrazine was evaluated for 26 functional groups in the functional group evaluation (FGE) kit. Accurate and rapid evaluation of the compatibility of functional groups, such as nitrogen-containing heterocycles important in drug discovery research, will enhance the application of this reaction in drug discovery research. These data will be used for predictive studies of organic synthesis methods based on machine learning. In addition, these studies led to discoveries such as the unexpected positive additive effects of carboxylic acids, indicating that the FGE kit can propel serendipitous discoveries.

Aiming at shedding light on the molecular interactions in deep eutectic solvents (DESs), the DESs based on tetrabutylammonium bromide (TBAB) as hydrogen bond acceptor (HBA) and carboxylic acids (CAs) (formic acid (FA), oxalic acid (OA), and malonic acid (MA)) as hydrogen bond donor (HBD) were investigated by both experimental and theoretical techniques. The thermal behaviors of the prepared DESs were investigated by differential scanning calorimetry (DSC) method. In order to study the hydrogen bond formation between the DESs constituents, the FT-IR analysis was carried out. The large positive deviations of the iso solvent activity lines of ternary HBA + HBD + 2-propanol mixtures determined by the isopiestic technique from the semi-ideal behavior indicate that CAs interact strongly with TBAB and therefore they can form DESs. Molecular dynamics (MD) simulations were performed to present an atomic-scale image of the components and describe the microstructure of DESs. From the MD simulations, the radial distribution functions (RDFs), coordination numbers (CNs), combined distribution functions (CDFs), and spatial distribution functions (SDFs) were calculated to investigate the interaction between the components and three-dimensional visualization of the DESs. The obtained results confirmed the importance of hydrogen bonds in the formation of TBAB/CAs DESs.

We designed and synthesized a ureido-linked zinc bisporphyrinate [Zn2(UBis)]. CD spectra show that this zinc bisporphyrinate has the ability to sense the chirality of chiral carboxylic acids without derivatization. Our studies suggest that the phenyl ring in the linker forms π-π interactions with porphyrin planes and that the carboxylic acid is coordinated to the zinc in the host-guest complex. DFT calculations show that the bisporphyrin adopts a \"Z\"-shaped configuration, and that the ureido group forms hydrogen bonds with carboxylic acids. The combination of π-π interactions, coordination interactions and hydrogen bonding interactions leads to the chirality sensing ability of [Zn2(UBis)].

We report an iron-catalyzed decarboxylative C(sp3)-O bond-forming reaction under mild, base-free conditions with visible light irradiation. The transformation uses readily available and structurally diverse carboxylic acids, iron photocatalyst, and 2,2,6,6-tetramethylpiperidine 1-oxyl (TEMPO) derivatives as oxygenation reagents. The process exhibits a broad scope in acids possessing a wide range of stereoelectronic properties and functional groups. The developed reaction was applied to late-stage oxygenation of a series of bio-active molecules. The reaction leverages the ability of iron complexes to generate carbon-centered radicals directly from carboxylic acids by photoinduced carboxylate-to-iron charge transfer. Kinetic, electrochemical, EPR, UV/Vis, HRMS, and DFT studies revealed that TEMPO has a triple role in the reaction: as an oxygenation reagent, an oxidant to turn over the Fe-catalyst, and an internal base for the carboxylic acid deprotonation. The obtained TEMPO adducts represent versatile synthetic intermediates that were further engaged in C-C and C-heteroatom bond-forming reactions using commercial organo-photocatalysts and nucleophilic reagents.

Soil alkalization is an important environmental factor limiting crop production. Despite the importance of root secretion in the response of plants to alkali stress, the regulatory mechanism is unclear. In this study, we applied a widely targeted metabolomics approach using a local MS/MS data library constructed with authentic standards to identify and quantify root exudates of wheat under salt and alkali stresses. The regulatory mechanism of root secretion in alkali-stressed wheat plants was analyzed by determining transcriptional and metabolic responses. Our primary focus was alkali stress-induced secreted metabolites (AISMs) that showed a higher secretion rate in alkali-stressed plants than in control and salt-stressed plants. This secretion was mainly induced by high-pH stress. We discovered 55 AISMs containing -COOH groups, including 23 fatty acids, 4 amino acids, 1 amino acid derivative, 7 dipeptides, 5 organic acids, 9 phenolic acids, and 6 others. In the roots, we also discovered 29 metabolites with higher levels under alkali stress than under control and salt stress conditions, including 2 fatty acids, 3 amino acid derivatives, 1 dipeptide, 2 organic acids, and 11 phenolic acids. These alkali stress-induced accumulated carboxylic acids may support continuous root secretion during the response of wheat plants to alkali stress. In the roots, RNAseq analysis indicated that 5 6-phosphofructokinase (glycolysis rate-limiting enzyme) genes, 16 key fatty acid synthesis genes, and 122 phenolic acid synthesis genes have higher expression levels under alkali stress than under control and salt stress conditions. We propose that the secretion of multiple types of metabolites with a -COOH group is an important pH regulation strategy for alkali-stressed wheat plants. Enhanced glycolysis, fatty acid synthesis, and phenolic acid synthesis will provide more energy and substrates for root secretion during the response of wheat to alkali stress.

Palladium-catalyzed enantioselective C(sp3)-H functionalization reactions has attracted considerable attention due to its ability for the synthesis of enantiomerically enriched molecules and stimulation of novel retrosynthetic disconnections. Understanding the reaction mechanism, especially the stereochemical process of the reaction, is crucial for the rational design of more efficient catalytic systems. Previously, we developed a Pd(II)/sulfoxide-2-hydroxypridine (SOHP) catalytic system for asymmetric C(sp3)-H functionalization reactions. In this study, we focused on unraveling the chemistry of chiral palladacycles involved in the Pd(II)-catalyzed enantioselective C(sp3)-H functionalization. We have isolated key palladacycle intermediates involved in the enantioselective β-C(sp3)-H arylation of carboxylic acids catalyzed by the Pd(II)/SOHP system. These palladacycles, exhibiting ligand-induced chirality, provided a significant opportunity to investigate the stereochemical process and the ligand effect in this asymmetric C-H functionalization. Our investigation provided direct evidence for the C-H palladation step as the enantioselectivity-determining step, which forms diastereomeric palladacycles that exhibited preservation of chirality in the functionalization step. DFT calculations provided insights into the chiral induction in palladacycle formation. This work highlights the value of chiral palladacycle chemistry in offering mechanistic insights into the Pd(II)-catalyzed asymmetric C(sp3)-H functionalization reactions.

Chloroethenes are widely used as solvent in the metal industry and the dry cleaning industry, but their spillage into soil and groundwater due to improper handling has negatively impacted human health. Bioremediation using microorganisms is one of the technologies to clean up soil and groundwater contaminated with chloroethenes. In this study, we examined the bioremediation of chloroethene-contaminated soil using wine pomace extract (WPE). WPE is a liquid containing seven major carboxylic acids and other substances extracted from grape pomace produced in winemaking. WPE clearly promoted the anaerobic bioremediation of chloroethenes. In the tetrachloroethene (PCE) degradation test that used fractions derived from WPE, the water-eluted fraction containing L-lactic acid, L-tartaric acid, and others promoted the dechlorination of PCE, whereas the methanol-eluted fraction containing mainly syringic acid did not. In another PCE degradation test that used L-lactic acid, L-tartaric acid, and syringic acid test solutions, L-lactic acid and L-tartaric acid enhanced the dechlorination of PCE, but syringic acid did not. The results suggest that L-lactic acid and L-tartaric acid in WPE function as hydrogen donors in the anaerobic microbial degradation of chloroethene. This technology realizes environmental remediation through the effective use of food by-products.

Carboxylic acids are key pharmacophoric elements in many molecules. They can be seen as a problem by some, due to perceived permeability challenges, potential for high plasma protein binding and the risk of forming reactive metabolites due to acyl-glucuronidation. By others they are viewed more favorably as they can decrease lipophilicity by adding an ionizable center which can be beneficial for solubility, and can add enthalpic interactions with the target protein. However, there are many instances where the replacement of a carboxylic acid with a bioisosteric group is required. This has led to the development of a number of ionizable groups which sufficiently mimic the carboxylic acid functionality whilst improving, for example, the metabolic profile of the molecule in question. An alternative strategy involves replacement of the carboxylate by neutral functional groups. This review initially details carefully selected examples whereby tetrazoles, acyl sulfonamides or isoxazolols have been beneficially utilized as carboxylic acid bioisosteres altering physicohemical properties, interactions with the target and metabolism and/or pharmacokinetics, before delving further into the binding mode of carboxylic acid derivatives with their target proteins. This analysis highlights new ways to consider the replacement of carboxylic acids by neutral bioisosteric groups which either rely on hydrogen bonds or cation-π interactions. It should serve as a useful guide for scientists working in drug discovery.

The selection of a \"perfect tool\" for the theoretical determination of acid-base dissociation constants (Ka) is still puzzling. Recently, we developed a user-friendly model exploiting CAM-B3LYP for determining pKa with impressive reliability. Herein, a new challenge is faced, examining a panel of functionals belonging to different rungs of the \"Jacob\'s ladder\" organization, which classifies functionals according to their level of theory. Specifically, meta-generalized gradient approximations (GGAs), hybrid-GGAs, and the more complex range-separated hybrid (RSH)-GGAs were investigated in predicting the pKa of differently substituted carboxylic acids. Therefore, CAM-B3LYP, WB97XD, B3PW91, PBE1PBE, PBEPBE and TPSSTPSS were used, with 6-311G+(d,p) as the basis set and the solvation model based on density (SMD). CAM-B3LYP showed the lowest mean absolute error value (MAE = 0.23) with relatively high processing time. PBE1PBE and B3PW91 provided satisfactory predictions (MAE = 0.34 and 0.38, respectively) with moderate computational time cost, while PBEPBE, TPSSTPSS and WB97XD led to unreliable results (MAE > 1). These findings validate the reliability of our model in predicting carboxylic acids pKa, with MAE well below 0.5 units, using a simplistic theoretical level and a low-cost computational approach.