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Carboxylic acids (CAs) represent a large group of important molecules participating in various biologically significant processes. Analytical study of these compounds is typically performed by liquid chromatography (LC) combined with various types of detection. However, their analysis is often accompanied by a wide variety of problems depending on used separation system or detection method. The dominant ones are: i) poor chromatographic behavior of the CAs in reversed-phase LC; ii) absence of a chromophore (or fluorophore); iii) weak ionization in mass spectrometry (MS). To overcome these problems, targeted chemical modification, and derivatization, come into play. Therefore, derivatization still plays an important and, in many cases, irreplaceable role in sample preparation, and new derivatization methods of CAs are constantly being developed. The most commonly used type of reaction for CAs derivatization is amidation. In recent years, an increased interest in the isotopic labeling derivatization method has been observed. In this review, we comprehensively summarize the possibilities and actual trends in the derivatization of CAs that have been published over the past decade. [Display omitted] • Liquid chromatography coupled with mass spectrometry is predominant combination. • Amidation is the most used type of derivatization reaction. • Chiral derivatization stagnates in this field. • Stable isotope labeling is favorably used in analysis of large number of analytes. • Development of greener derivatization reagents for carboxylic acids is needed. [ABSTRACT FROM AUTHOR]

[Display omitted] 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. [ABSTRACT FROM AUTHOR]

[Display omitted] • A 3 B type asymmetric metallo phthalocyanines were synthesized. • These phthalocyanines contain carboxylic acid and tert -butyl groups. • Photophysical and photochemical properties of phthalocyanines were investigated. • Phthalocyanines displayed desirable singlet oxygen, photodegradation and fluorescence properties. In this study, A 3 B type asymmetric magnesium(II), zinc(II) and indium(III)chloro phthalocyanine derivatives bearing carboxylic acid and tert -butyl groups were synthesized and their photochemical, photophysical and aggregation properties for photodynamic therapy (PDT) application were investigated. In the first part of the study; phthalonitriles, which are the starting materials, were synthesized and then different phthalocyanine compounds were obtained from the synthesized phthalonitriles in the second part. The synthesized compounds were characterized using different techniques. At the same time, the photophysical and photochemical properties of the synthesized compounds were also investigated. The calculated singlet oxygen quantum values in DMSO are 0.30 for MgPc , 0.72 for ZnPc , and 0.62 for InPc in and these values in DMF are 0.25 for MgPc , 0.68 for ZnPc , and 0.60 for InPc after photochemical studies. The obtained results proved that the contribution of the substituents increased the therapeutic efficacy. Finally, our results show that all Pc derivatives have displayed desirable singlet oxygen, photodegradation, fluorescence and aggregation properties for PDT studies. [ABSTRACT FROM AUTHOR]

[Display omitted] • First UV absorption spectrum of acrylic acid/acrylate in water reported. • Absorbance decreased log linearly with wavelength with no minor absorption bands. • Long pathlength UV–Vis allows study of compounds with low molar absorptivities. • Acrylate weakly absorbs solar radiation relevant to aqueous environmental systems. Acrylic acid is an important compound widely used in industry with multiple commercial applications, and it is also a key intermediate in the marine organosulfur cycle. However, the fundamental ultraviolet (UV) absorption spectrum of acrylic acid or its conjugate base, acrylate (pK a = 4.25 at 20 °C) have not been determined in water. In this paper, we determined the absorption spectrum of acrylate in aqueous solution at pH 7.2 and 20 °C between 207 and 400 nm. The molar absorptivity decreased rapidly from 3958 M−1 cm−1 at 207 nm to a non-detectable value at wavelengths greater than 330 nm, with weak absorption at wavelengths greater than 290 nm (e.g., ɛ 290nm 2.7 M−1 cm−1). No discernable absorption bands were observed in the absorption spectrum. Excellent agreement was observed when comparing absorption spectra obtained (1) with two different spectrophotometers and (2) with standards prepared from either newly purchased sodium acrylate or from acrylate obtained from the base hydrolysis of dimethylsulfoniopropionate. Wavelength-dependent molar absorptivities were constant at pH 7.2 over a range of acrylate concentrations from 25 to 135 μM. The absorption spectrum red shifted when the solution pH increased from 2.8 to 8.2, with an isosbestic point observed at 214 nm indicating two exchangeable species in solution. Our study provides the first detailed UV absorption spectra of acrylic acid and acrylate in aqueous solution, with important implications regarding the detection and study of these compounds in environmental settings and commercial applications. [ABSTRACT FROM AUTHOR]

A wide range of carboxylic acids, amides, and esters were synthesized from aryl iodide utilizing sodium oleate as surfactant in presence of a simple Pd(OAc) 2 catalyst in water under ambient temperature and CO pressure. Applying this protocol, several drug molecules such as niacin, and mefenamic acid alike compound were synthesized in good yields. [Display omitted] Palladium acetate [Pd(OAc) 2 ] catalyzed reaction of aryl iodide utilizing sodium oleate as surfactant was demonstrated in water under ambient temperature and carbon monoxide pressure. Aryl carboxylic acid with different electron withdrawing and donating substituents, and multi -substituted acid derivatives were synthesized in good to excellent isolated yields. Notably, this protocol was also applicable for one pot synthesis of various amide and ester derivatives. Several drug molecules such as niacin, and mefenamic acid alike compound were also obtained in good, isolated yields. [ABSTRACT FROM AUTHOR]

[Display omitted] • A mild and efficient palladium-catalyzed carbonylation procedure toward the preparation of (fluoro)malonate derivatives has been developed. • Various (fluoro)malonate compounds were prepared in good to excellent yields with broad functional group tolerance. • The reaction can be scaled-up and performed under atmospheric pressure. Traditional procedures toward 2-fluoromalonates tend to meet overfluorination. Herein, we describe a mild and efficient palladium-catalyzed carbonylative strategy for the synthesis of dialkyl 2-fluoromalonate derivatives avoided the mentioned challenges. By this new procedure, a range of malonates and difluoromalonate derivatives were prepared with good functional-group tolerance and excellent chemoselectivity. This procedure can also be applied in the late-stage carbonylation of various bioactive molecules. Furthermore, a low-pressure experiment and two scale-up reactions were performed smoothly in good to excellent yield. [ABSTRACT FROM AUTHOR]

Abstract In this paper, the contact configuration of single molecular junction is controlled through side group, which is explored by electrochemical jump-to-contact STM break junction. The conductance values of 2-methoxy-1,3-benzenedicarboxylic acid (2-M-1,3-BDC) is around 10–3.65 G0, which is different from that of 5-methoxy-1,3-benzenedicarboxylic acid (5-M-1,3-BDC) with 10–3.20 G0. Interestingly, the conductance value of 2-M-1,3-BDC is the same as that of 1,3-benzenedicarboxaldehyde (1,3-BDCA), while single molecular junctions of 5-M-1,3-BDC and 1,3-benzenedicarboxylic acid (1,3-BDC) give out similar conductance value. Since 1,3-BDCA binds to the Cu electrode through one oxygen atom, the dominated contact configuration for 1,3-BDC is through two oxygen atoms. The different conductance values between 2-M-1,3-BDC and 5-M-1,3-BDC can be attributed to the different contact configurations caused by the position of the side group. The current work provides a feasible way to control the contact configuration between the anchoring group and the electrode, which may be useful in designing future molecular electronics.

The research including used anew adsorbent substance collected from sandstorms which arrived to Mosul city to study adsorption of Benzoic acid and some substituted and application of kinetics Models (pseudo first and second order reaction ) Elovich model kinetics and determination of thermodynamic function for adsorption process as well as the probability sticking for acids molecules on surface (S*)and the appareant activation energy , the isothermic constants were determined for frendlich ,Langmir,Tempkin at different temperature and factors affecting on adsorption process ,the results gives indicates that the physical mechanism which predominate and some times physical and chemical the adsorption was increased and desorption decreased ,this process non spotonous and need lower energy to happened

Introduction. The possibility of using monocarboxylic acids as a lubricant composition additive, and the effect of their concentration in lubricant on the evolution of the friction factor of a brass-steel couple, as well as the morphology of the film surface under friction is considered. The work objective is to study the effect of the concentration of carboxylic acids in the lubricant composition on the evolution of the friction factor of copper – steel alloy.Materials and Methods. Tribological studies of a brass-steel friction couple in aqueous solutions of monocarboxylic acids with the concentrations of 0.025; 0.05; 0.1; 0.2; 0.5 mol/l are carried out. Using scanning electron microscopy, we have studied the morphology of the servovite film surface that is formed on a steel disk after frictional interaction of a brasssteel couple in aqueous solutions of acids with the concentration of 0.1 mol/l.Research Results. Tribological characteristics of the brasssteel tribocoupling in aqueous solutions of carboxylic acids of various concentrations are studied. The optimum acid concentration in the lubricant composition is specified. Herewith, a selective transfer and a wearless friction regime are implemented under friction of the brass 59–steel 40X couple. A decrease in the friction ratio to 0.009 and 0.007 is found out under friction in aqueous solutions of valeric and caproic acids, respectively. The formation of an anti-friction film on the steel surface is identified through the scanning electron microscopy. It is established that the film formed in an aqueous solution of caproic acid has a denser structure in comparison with the film formed under friction in aqueous solutions of butyric and caproic acids.Discussion and Conclusions. Thus, the tribological studies of a brass-steel friction couple in aqueous acid solutions show that the optimum molar acid concentration in the lubricant composition is 0.1 mol/l. At this acid concentration, the values of the friction factor characteristic of the wearless mode are attained.

A large library of derivatives based on the scaffold of 2-(benzylsulfinyl)benzoic acid were synthesised and tested as atypical inhibitors against four different isoforms of human carbonic anhydrase (hCA I, II, IX and XII, EC 4.2.1.1). The exploration of the chemical space around the main functional groups led to the discovery of selective hCA IX inhibitors in the micromolar/nanomolar range, thus establishing robust structure-activity relationships within this versatile scaffold. HPLC separation of some selected chiral compounds and biological evaluation of the corresponding enantiomers was performed along with molecular modelling studies on the most active derivatives.

Smooth surfaces are conducive to improving the lubrication of gears in mechanical systems. In this study, chemical mechanical polishing (CMP) was used to process 18CrNiMo7-6 case hardening steel, a typical material for gears. The results reveal that compared with formic acid and oxalic acid, citric acid can be used as a suitable complexing agent without causing apparent corrosion, probably due to the fact of its relatively stable adsorption. A synergistic effect exists between citric acid and H2O2. At pH 3, with 0.067 M citric acid and 1 wt% H2O2, a satisfactory CMP performance (i.e., a 514 nm/min material removal rate (MRR) and a 0.85 nm surface roughness Sa) was achieved. After polishing, no observable defects were found on the surface, and no discernible processing damage occurred to the substrate. In terms of the CMP’s mechanism, iron is first oxidized to Fe2+ and Fe3+, which then react with citric acid to form complexes. On the one hand, most of the complexes may stay on the surface to prevent further corrosion and, thus, the surface quality is excellent. On the other hand, the complexes may reduce the surface integrity and, thus, the MRR is high. The findings open new avenues for attaining ultra-smooth steel surfaces with CMP through controlling corrosive wear.

The X-ray crystal structure determination of the glutaric acid-amide derivative, 4-ClC6H4N(H)C(=O)(CH2)3C(=O)OH (1), is described. The backbone of the molecule adopts an extended, all-trans configuration but the terminal carboxylic acid and phenyl resides are twisted out of the plane through the bridging atoms, as seen in the torsion angles of O(carboxylic acid)–C(m)–C(m)–C(m) [13.9(5)°] and C(m)–N–C(p)–C(p) [47.1(4)°]; m = methylene and p = phenyl. The most striking feature of the molecular packing is the formation of supramolecular tapes mediated by carboxylic acid-O–H⋯O(carbonyl) and amide-N–H⋯O(amide) hydrogen bonding.

We propose an approach for monitoring the concentration of dissociated carboxylic acid species in dilute aqueous solution. The dissociated acid species are quantified employing inline Raman spectroscopy in combination with indirect hard modeling (IHM) and multivariate curve resolution (MCR). We introduce two different titration-based hard model (HM) calibration procedures for a single mono- or polyprotic acid in water with well-known (method A) or unknown (method B) acid dissociation constants p K a. In both methods, spectra of only one acid species in water are prepared for each acid species. These spectra are used for the construction of HMs. For method A, the HMs are calibrated with calculated ideal dissociation equilibria. For method B, we estimate p K a values by fitting ideal acid dissociation equilibria to acid peak areas that are obtained from a spectral HM. The HM in turn is constructed on the basis of MCR data. Thus, method B on the basis of IHM is independent of a priori known p K a values, but instead provides them as part of the calibration procedure. As a detailed example, we analyze itaconic acid in aqueous solution. For all acid species and water, we obtain low HM errors of < 2.87 × 10−4mol mol−1 in the cases of both methods A and B. With only four calibration samples, IHM yields more accurate results than partial least squares regression. Furthermore, we apply our approach to formic, acetic, and citric acid in water, thereby verifying its generalizability as a process analytical technology for quantitative monitoring of processes containing carboxylic acids. [ABSTRACT FROM AUTHOR]

Herein, cobalt embedded in nitrogen-doped porous carbon (Co@NC) was developed as a robust heterogeneous catalyst for the dehydrogenative coupling of primary alcohols and hydroxides. With Co@NC as the first earth-abundant metal/carbon composite material for this transformation, numerous aromatic and aliphatic carboxylic acids were efficiently afforded. Notably, the newly prepared Co@NC was fabricated in a facile and straightforward manner and reused up to 15 recycle rounds without activity decay. It is also worth emphasizing that the catalyst recycling was realized via magnetic separation with no special treatment or activation. Additionally, further experiments elucidated the pivotal role of the cobalt and nitrogen elements dispersed in the carbon matrix as well as the hierarchical porosity (micro-/meso-pores) in the catalytic activity and recyclability. Considering the active sites of Co@NC, we envisioned that the Co–N species was the most active site, while other active sites such as Co–O, Co0 species and free N-doped carbon were also present, but demonstrating lower activity or stability in comparison with the Co–N species. Additional mechanistic investigations were carried out to gain more insights into the possible reaction pathways. We found that the aldehyde was identified as a crucial intermediate, and two possible pathways were proposed for this catalytic process. Image 1 • Co embedded in nitrogen-doped porous carbon as a robust heterogeneous catalyst. • The 1st earth-abundant metal/carbon material for the alcohol dehydrogenation to acids. • Recyclable for 15 times by magnetic separation without special treatment/activation. • Unique porous structure and well-dispersion of Co and N within the carbon matrix. • Investigation of active catalytic sites and reaction pathways. [ABSTRACT FROM AUTHOR]

Oxidation of primary alcohols to carboxylic acids is a fundamental transformation in organic chemistry, yet despite its simplicity, extensive use, and relationship to pH, it remains a subject of active research for synthetic organic chemists. Since 2013, a great number of new methods have emerged that utilize transition-metal compounds as catalysts for acceptorless dehydrogenation of alcohols to carboxylates. The interest in this reaction is explained by its atom economy, which is in accord with the principles of sustainability and green chemistry. Therefore, the methods for the direct synthesis of carboxylic acids from alcohols is ripe for a modern survey, which we provide in this review. 1 Introduction 2 Thermodynamics of Primary Alcohol Oxidation 3 Oxometalate Oxidation 4 Transfer Dehydrogenation 5 Acceptorless Dehydrogenation 6 Electrochemical Methods 7 Outlook [ABSTRACT FROM AUTHOR]

Pollen tube growth is inhibited and promoted by long- and short-chain carboxylic acids, respectively, but is not affected by formic acid. For auxin- and gibberellin-induced elongation of in vitro cultured epicotyl segments of adzuki bean (Vigna angularis), a series of carboxylic acids showed similar effects as that on pollen tube growth except that formic acid showed the strongest promotive effect. The effects of formic acid and GA3 on IAA-induced elongation were additive and both were strongly inhibited by inhibitors of cellulose synthesis (coumarin) and microtubule formation (colchicine). Formic acid, possibly by incorporation into the segments, prolonged the promotion by IAA and GA3 of the elongation of epicotyl segments. Based on these results and later advances in our understanding of metabolism and the role of formic acid in protecting against oxidative stress, a possible role of formic acid on stem elongation is discussed. [ABSTRACT FROM AUTHOR]

Previous studies have found that alkylated polycyclic aromatic hydrocarbons (alkyl-PAHs) were more abundant in petrogenic sources (e.g., crude oil and its refined products) than pyrogenic sources of incomplete combustion. While urinary hydroxylated metabolites of unsubstituted PAHs have been widely used as biomarkers of PAHs exposures, little information is available as to the occurrence of alkyl-PAH metabolites. In this study, we have detected carboxylic acid metabolites of alkyl-naphthalene (2-NAPCA) and alkyl-phenanthrene (2-PHECA) in 314 urine samples repeatedly collected from 45 Los Angeles residents before, during, and after they spent ten weeks in Beijing in summers of 2014–2017. We found that traveling from Los Angeles to Beijing led to 348% (95% CI: 243 to 485%) and 209% (95% CI: 149 to 282%) increases in 2-NAPCA and 2-PHECA concentrations, respectively, which returned to baseline levels after participants came back to Los Angeles. The concentration ratio between 2-PHECA and hydroxy-phenanthrenes was significantly (p

In order to compete with petroleum-based fuel and chemicals, engineering a robust biocatalyst that can convert renewable feedstocks into biorenewable chemicals, such as carboxylic acids, is increasingly important. However, product toxicity is often problematic. In this study, the toxicity of the carboxylic acids hexanoic, octanoic, and decanoic acid on Saccharomyces cerevisiae was investigated, with a focus on octanoic acid. These compounds are completely inhibitory at concentrations of magnitude 1 mM, and the toxicity increases as chain length increases and as media pH decreases. Transciptome analysis, reconstruction of gene regulatory network, and network component analysis suggested decreased membrane integrity during challenge with octanoic acid. This was confirmed by quantification of dose-dependent and chain length-dependent induction of membrane leakage, though membrane fluidity was not affected. This induction of membrane leakage could be significantly decreased by a period of pre-adaptation, and this pre-adaptation was accompanied by increased oleic acid content in the membrane, significantly increased production of saturated lipids relative to unsaturated lipids, and a significant increase in the average lipid chain length in the membrane. However, during adaptation cell surface hydrophobicity was not altered. The supplementation of oleic acid to the medium not only elevated the tolerance of yeast cells to octanoic acid but also attenuated the membrane leakiness. However, while attempts to mimic the oleic acid supplementation effects through expression of the Trichoplusia ni acyl-CoA Δ9 desaturase OLE1(TniNPVE desaturase) were able to increase the oleic acid content, the magnitude of the increase was not sufficient to reproduce the supplementation effect and increase octanoic acid tolerance. Similarly, introduction of cyclopropanated fatty acids through expression of the Escherichia coli cfa gene was not helpful for tolerance. Thus, we have provided quantitative evidence that carboxylic acids damage the yeast membrane and that manipulation of the lipid content of the membrane can increase tolerance, and possibly production, of these valuable products.

Due to the environmental impact caused by incorrect disposal and the non-biodegradability of synthetic polymers, the packaging sector seeks renewable raw materials. An alternative is the utilization of natural renewable polymer, such as thermoplastic starch (TPS), mixed with synthetics. However, the chemical incompatibility between these two materials leads to the use of a compatibilizer agent. Even though the compatibilizer effect of carboxylic acid on TPS blends have been studied, the correlation between the carboxylic acid and the starch source has not been investigated yet. Thus, this study focuses on the effects of added carboxylic acids (myristic (C14) and stearic (C18) acid) and the starch sources (corn, cassava, and potato) on the properties and microstructure of blends with TPS/PP (70/30). The results suggested that the compatibilizer effect of acids depends on the starch source and the length of the acid chain, where cassava blends with C14 showed better results. Acid insertion increased tensile strength and deformation at break, but reduced the elastic modulus, indicating a plasticizer effect. This behavior was related to the formation of amylose and lipid complexes (endogenous or added) during heating. Torque reduction and Tg displacement were also observed for acid blends. The SEM images showed two different morphological dispersions and a non-gelatinization effect due to the acid insertion. Results suggested that acids act differently according to the starch source. [ABSTRACT FROM AUTHOR]

The development of robust and cheap photocatalyst systems for visible-light induced organic substrate transformations is a significant uprising research topic at the crossroads of green chemistry and modern synthetic methodology. Atom economy, efficiency and selectivity are key parameters for the future practical applicability of the specific processes catalyzed. In this context, we report a simple and sustainable oxygen-dependent route for oxidizing various aromatic and aliphatic aldehydes to the corresponding carboxylic acids at room temperature under visible light and sunlight irradiation mediated by cobalt phthalocyanine tetrasulfonic acid (CoPcS) supported on reduced graphene oxide (RGO). Remarkably, products are obtained with (81–100)% conversion and 100% selectivity. [ABSTRACT FROM AUTHOR]

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., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2024 Choi, Nawachi, Saito, Kondo, Morimoto and Ohshima.)

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.

Here we report the challenging O-trifluoromethylation of carboxylic acids via the formation and activation of acyloxy(phenyl)trifluoromethyl-λ 3 -iodanes. The method provides an easy access to various potentially valuable and hitherto elusive trifluoromethyl carboxylic esters. A remarkably wide range of substrates with commonly encountered functional groups are compatible with this reaction, including aromatic and aliphatic carboxylic acids, as well as Food and Drug Administration (FDA) approved drugs and pharmaceutically relevant molecules. The reaction mechanism and the origins of the enhanced reactivity by zinc chloride (ZnCl 2 ) were discussed from experimental evidence and density functional theory (DFT) calculation., (© 2024 Wiley‐VCH GmbH.)

A new electrochemical transformation is presented that enables chemists to couple simple alkyl carboxylic acid derivatives with an electrophilic amine reagent to construct C(sp 3 )-N bond. The success of this reaction hinges on the merging of cooperative electrochemical reduction with nickel catalysis. The chemistry exhibits a high degree of practicality, showcasing its wide applicability with 1°, 2°, 3° carboxylic acids and remarkable compatibility with diverse functional groups, even in the realm of late-stage functionalization. Furthermore, extensive mechanistic studies have unveiled the engagement of alkyl radicals and iminyl radicals; and elucidated the multifaceted roles played by i Pr 2 O, Ni catalyst, and electricity., (© 2024 Wiley-VCH GmbH.)

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.

The mechanisms of Csp2–H activation of aldehydes to yield carboxylic acids catalyzed by NHPI have been investigated with M06‐2X‐D3/ma‐def2‐TZVP method and basis set in the Universal Solvation Model Based on Solute Electron Density (SMD). The computational results suggest that the activation of NHPI, rather than aldehydes, would be finished by triplet O2 with lower energy barrier. The obtained radicals PINO and HOO˙ could help to achieve this Csp2–H activation of aldehydes, then triplet O2 would continue to react with generated intermediate to obtain Criegee intermediate radical; the following H‐shift reactions happened to produce Criegee intermediate; finally, SN2 reaction would help to yield the final product carboxylic acid. Meanwhile, the obtained carboxylic acid radical captures one proton to yield carboxylic acid. The localized orbital locator (LOL) isosurfaces of pi orbitals, and electron spin density isosurface graphs could reveal the single electron transfer process. The results would provide valuable insights into these types of interactions and related ones. [ABSTRACT FROM AUTHOR]

Many mosquito behaviours that are critical for survival and reproduction depend upon timely responses to chemical cues. Of interest are the effects of volatile organic compounds like carboxylic acids (CAs) that are released by potential blood meal hosts. Short chain CAs are among the primary attractants for host‐seeking females and influence host selection in vector species. Although the behavioural relevance of CA's has been established, less is known about the molecular receptive events that evoke responses to specific compounds, with the Ir family of chemoreceptors being broadly implicated in their detection. In this study, we demonstrate that Or orthologs from two vector species, Aedes aegypti (L.) and Aedes albopictus (Skuse), are selectively activated by straight chain carboxylic acids and that these responses are attenuated by the commercial insect repellant N,N‐Diethyl‐meta‐toluamide. Our results suggest that multiple chemoreceptors, representing diverse families, are able to mediate molecular responses to CAs and may therefore underlie important behaviours that directly impact disease‐transmission cycles. [ABSTRACT FROM AUTHOR]

Cellulose nanofibers (CNFs) have received considerable attention as reinforcing fillers due to their excellent and versatile properties, including physical, morphological, and chemical features. Despite many advantages of CNFs, the hydrophilic nature of CNFs significantly limits their use as fillers. In this study, CNFs were modified by esterification with two kinds of carboxylic acids: valeric acid (VA) and hexanoic acid (HA). The degree of substitutions (DS) of VA-CNF and HA-CNF was 2.78 ± 0.04 and 2.61 ± 0.02, respectively. The dispersibility in an isopropanol solvent showed the controlled hydrophilicity of the modified CNFs. Moreover, the water contact angles of VA-CNF and HA-CNF were 79.2 ± 3.1° and 85.0 ± 1.7°, respectively, while the neat CNF was just 18.9 ± 1.6°. The thermogravimetric analysis (TGA) revealed that the modified CNFs have much better thermal stability than the neat CNFs. Also, the CNF films showed uniform-sized nano-porous structures after the modifications of CNFs. Combined with well-improved hydrophobicity, these multi-faceted results suggest that our esterification technique of CNFs can be applied in a wide range of eco-friendly materials applications. [ABSTRACT FROM AUTHOR]

Microbial conversion of lignocellulosic substrates to fuel and platform chemical intermediates offers a sustainable route to establish a viable bioeconomy. However, such approaches face a series of key technical, economic, and sustainability hurdles, including: incomplete substrate utilization, lignocellulosic hydrolysate, and/or end-product toxicity, inefficient product recovery, incompatible cultivation requirements, and insufficient productivity metrics. Development of a production host with native traits suitable for high productivity conversion of lignocellulosic substrates under process-relevant conditions offers a means to bypass the above-described hurdles and accelerate the development of microbial biocatalyst deployment. Clostridium tyrobutyricum, a native producer of short chain fatty acids, displays a series of characteristics that make it an ideal candidate for conversion of lignocellulosic substrates and thus represents a promising host for microbial production of diverse carboxylate-derived product suites. Herein, recent progress and future directions in the development of this bacterium as an industrial microbial cell factory, with emphases on the utilization of lignocellulosic substrates and metabolic engineering approaches, is reviewed.

With increasing global power demand, thermal energy storage technology could play a role ensuring a sustainable energy supply in power generation from renewable energy sources and power demand concentration. Hydrates have high potential as phase change materials (PCMs) for the use as a thermal energy storage medium. To develop thermal energy storage technology using a hydrate-based material, further investigation of thermophysical properties and the selection of a suitable hydrate are required. Tetrabutylphosphonium oxalate (TBPOx) ionic semiclathrate hydrate contains oxalic acid in salt form, as a guest compound, which is classified as carboxylic acid group with low environmental impact. In the present study, the phase equilibrium temperature and the dissociation heat of TBPOx hydrate were measured. The highest equilibrium temperature of the solid hydrate formed was 9.4°C at the mass fraction 0.35 of TBPOx in aqueous solution. The largest dissociation heat was 186.0 ± 0.5 kJ·kg−1 at the mass fraction of 0.35. Comparing with other PCMs with close phase equilibrium temperatures, TBPOx hydrate is superior in safety and sustainability. These results indicate that TBPOx hydrate would be suitable as the thermal storage medium for the general air conditioning systems.

ABSTRACT The phagocytic cells of the innate immune system are an essential first line of antimicrobial defense, and yet Candida albicans, one of the most problematic fungal pathogens, is capable of resisting the stresses imposed by the macrophage phagosome, eventually resulting in the destruction of the phagocyte. C. albicans rapidly adapts to the phagosome by upregulating multiple alternative carbon utilization pathways, particularly those for amino acids, carboxylic acids, and N-acetylglucosamine (GlcNAc). Here, we report that C. albicans recognizes these carbon sources both as crucial nutrients and as independent signals in its environment. Even in the presence of glucose, each carbon source promotes increased resistance to a unique profile of stressors; lactate promotes increased resistance to osmotic and cell wall stresses, amino acids increased resistance to oxidative and nitrosative stresses, and GlcNAc increased resistance to oxidative stress and caspofungin, while all three alternative carbon sources have been shown to induce resistance to fluconazole. Moreover, we show mutants incapable of utilizing these carbon sources, in particular, strains engineered to be defective in all three pathways, are significantly attenuated in both macrophage and mouse models, with additive effects observed as multiple carbon pathways are eliminated, suggesting that C. albicans simultaneously utilizes multiple carbon sources within the macrophage phagosome and during disseminated candidiasis. Taking the data together, we propose that, in addition to providing energy to the pathogen within host environments, alternative carbon sources serve as niche-specific priming signals that allow C. albicans to recognize microenvironments within the host and to prepare for stresses associated with that niche, thus promoting host adaptation and virulence. IMPORTANCE Candida albicans is a fungal pathogen and a significant cause of morbidity and mortality, particularly in people with defects, sometimes minor ones, in innate immunity. The phagocytes of the innate immune system, particularly macrophages and neutrophils, generally restrict this organism to its normal commensal niches, but C. albicans shows a robust and multifaceted response to these cell types. Inside macrophages, a key component of this response is the activation of multiple pathways for the utilization of alternative carbon sources, particularly amino acids, carboxylic acids, and N-acetylglucosamine. These carbon sources are key sources of energy and biomass but also independently promote stress resistance, induce cell wall alterations, and affect C. albicans interactions with macrophages. Engineered strains incapable of utilizing these alternative carbon pathways are attenuated in infection models. These data suggest that C. albicans recognizes nutrient composition as an indicator of specific host environments and tailors its responses accordingly.

Intracellular parasites such as Trypanosoma cruzi need to acquire valuable carbon sources from the host cell to replicate. Here, we investigated the energetic metabolism of T. cruzi during metacyclogenesis through the determination of enzymatic activities and quantification by HPLC of glycolytic and Krebs cycle short-chain carboxylic acids. Altered concentrations in pyruvate, acetate, succinate, and glycerate were measured during the growth of epimastigote in the complex medium BHI and their differentiation to trypomastigotes in the chemically defined medium, TAU3AAG. These alterations should represent significant differential metabolic modifications utilized by either form to generate energy. This paper is the first work dealing with the intracellular organic acid concentration measurement in T. cruzi parasites. Although it confirms the previous assumption of the importance of carbohydrate metabolism, it yields an essential improvement in T. cruzi metabolism knowledge.

Dronic acid derivatives, important drugs against bone diseases, may be synthesized from the corresponding substituted acetic acid either by reaction with phosphorus trichloride in methanesulfonic acid as the solvent or by using also phosphorous acid as the P-reactant if sulfolane is applied as the medium. The energetics of the two protocols were evaluated by high-level quantum chemical calculations on the formation of fenidronic acid and benzidronic acid. The second option, involving (HO)2P-O-PCl2 as the nucleophile, was found to be more favorable over the first variation, comprising Cl2P-O-SO2Me as the real reagent, especially for the case of benzidronate.

Carbon dioxide (CO2) is an important and appealing C1 building block in chemical synthesis due to its nontoxicity, abundance, availability and sustainability. Tremendous progress has been achieved in the chemical transformation of CO2 into high value-added organic chemicals. However, the asymmetric synthesis with CO2 to form enantioenriched molecules, especially the catalytic process, has lagged far behind. The enantioselective incorporation of CO2 into organic compounds is highly desirable, as the corresponding chiral products, such as carboxylic acids and amino acids, are common structural units in a vast array of natural products and biologically active compounds. Herein, we discuss recent progress toward the enantioselective incorporation of CO2 into organic molecules, which mainly rely on three strategies: 1) kinetic resolution or desymmetrization of epoxides with CO2 to form chiral cyclic carbonates and polycarbonates; 2) nucleophilic attack of O- or N-nucleophiles to CO2 in tandem with asymmetric C−O bond formation to prepare chiral cyclic carbonates and carbamates; 3) direct enantioselective nucleophilic attack of organometallic reagents to CO2 with asymmetric C−C bond formation. Finally, challenges and future outlook in this area are also presented. [ABSTRACT FROM AUTHOR]

Thermophysical properties, namely, density (?) and speed of sound (u) of binary mixtures of 1-butyl-3- methylimidazolium methyl sulphate [BMIM][MeSO4] ionic liquid (IL), with acetic acid or propionic acid have been measured in the mole fraction range from 0.1 to 1.0 at temperature ranging from 293.15 to 313.15 K at a 5 K interval, under atmospheric pressure of 101 kPa. From these measured values, the derived thermodynamic parameters, such as, isentropic compressibility (ks), deviation in isentropic compressibility (ks), excess molar volume (Vm E) and intermolecular free length (Lf) have been calculated. It is observed that Vm E and ks decrease with increasing the temperature. Furthermore, these values are negative in the whole range of binary compositions. The measured data and variations in derived thermodynamic values suggest that significant interactions occur when the IL forms a binary mixture with carboxylic acids. These derived thermodynamic parameters (Vm E, Lf and ks) are correlated byusing the Redlich-Kister polynomial equation to generate binary factors and standard errors. [ABSTRACT FROM AUTHOR]

The accumulation of short-chain carboxylic acids (SCCAs), such as acetic acid (C2), propionic acid (C3), butyric acid (C4), and valeric acid (C5), produced by acetogens in the anaerobic digestion (AD) process hampers the maintenance of stable AD processes in biomethane production. The conversion of various SCCAs to the corresponding alcohols can be a good solution not only for utilizing abandoned or harmful SCCAs and producing useful alcohols but also for increasing the efficiency of the biogas production process. ACT01_02765 (acyl-CoA transferase) from Megasphaera hexanoica quickly and easily converted C2-C8 carboxylic acids into the corresponding alcohols in Escherichia coli with AdhE2 (alcohol dehydrogenase) from Clostridium acetobutylicum. E. coli (ACT01_02765 and AdhE2) converted carboxylic acids to the corresponding alcohols with a conversion yield that was approximately 40 times higher and a conversion rate that was approximately 10–50 times faster than those of E. coli (Ptb-Buk and AdhE2). The enzymatic machinery in E. coli (ACT01_02765 and AdhE2) is effective for carboxylic acids of different carbon chain lengths, resulting in the production of propanol, butanol, pentanol, hexanol, heptanol, and octanol. [ABSTRACT FROM AUTHOR]

We present an economical and facile catalytic reduction process of carboxylic acids for the synthesis of alcohols. This pyridine‐catalyzed strategy operates through addition of carboxylic acids with methyl propiolate followed by NaBH4 reduction or unexpected ester exchange, providing the corresponding primary alcohols and esters, respectively. A range of carboxylic acids bearing other reductive groups (e. g. halogen, cyano, nitro, ester and double bond) are accessed with uniformly high chemoselectivity. The use of environmentally benign, convenient and safe procedure also makes this catalytic protocol attractive for practical application. [ABSTRACT FROM AUTHOR]

Controlled‐molecular‐weight‐distribution polymerization of sodium citrate in aqueous solution is successfully performed by Kolbe electrolysis reaction. It can be carried out in aqueous solution and no initiator and catalyst need to be added specially in this new polymerization procedure. The molecular weight of polymerization product linear rises with increasing conversion rate, and its distribution is maintained relatively narrowly (Mw/Mn < 1.55). The molecular weight and its distribution are obviously affected by a couple of elements, such as reaction temperature, as well as the kinds and amount of addition neutral salt ions in electrolysis solution. Kolbe electrolysis can realize the controlled‐molecular‐weight‐distribution polymerization of sodium citrate monomer effectively, which expands the scope of non‐olefin monomers used for controlled‐molecular‐weight‐distribution polymerization. [ABSTRACT FROM AUTHOR]

A novel post-synthetic method combining the microwave (MW)-assisted dealumination and hydrothermal (HT) alkaline treatment for obtaining mesoporous Y zeolite catalysts is presented. In the first-step MW-assisted dealumination of the pristine Y zeolite, both the mineral acid (i.e. hydrochloric acid, HCl) and organic carboxylic acids (e.g. oxalic and diethylenetriaminepentaacetic acid) were used (all at 0.16 M), and their effects on the physical and chemical properties of the resulting modified zeolites (after the identical HT alkaline treatment using 0.2 M sodium hydroxide solution) are studied in detail by comprehensive characterisation of the bulk silicon-to-aluminium (SAR) ratio, crystallinity and textural properties. The findings show that, in the developed sequential method, (i) HCl was only effective to achieve the hydrolysis of the zeolite, (ii) carboxylic acids with the function of chelation was very capable of extracting Al species and creating mesopores, and (iii) the mesopores formation is a function of the number of coordination sites in the carboxylic acid. The hierarchical feature of the mesopores in the modified zeolites (using carboxylic acids) was probed by the model reaction of aldol condensation of 1-heptanal with benzaldehyde for the selective formation of jasminaldehyde. The normalised selectivity to jasminaldehyde (with respect to the strong acidity) was proportionally related to the specific mesopores volume of the zeolites, revealing hierarchical porous networks in the relevant modified Y zeolites and indicating the effect of hierarchical mesopores in the zeolites on their catalytic performance. [ABSTRACT FROM AUTHOR]

The waterborne polyurethane (WPU) with different carboxylic acid group contents were prepared by a prepolymer method, adopting polycarbonate diol (PCDL) as soft segments and isophorone diisocyanate (IPDI) as hard segments. The different amounts of 2,2-dimethylolbutyric acid (DMPA) as hydrophilic chain extender were introduced into polyurethane molecular for studying the effect on microstructure and properties. The solid content, pH value and viscosity measurement were used to characterize the performance of WPU emulsion. The fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), thermogravimetric (TG), differential scanning calorimetry (DSC), dynamic mechanical analysis (DMA), water contact angle tester and mechanical testing machine were utilized to measure the structure, crystallization performance, thermal stability, low temperature flexibility, wetting performance and mechanical properties of WPU films, respectively. The test value of impact, adhesive, flexibility and pencil hardness on tinplate of WPU coatings were obtained for observing film properties. The results indicated that the emulsification effect increase with the increased DMPA contents. The decomposition temperature of WPU films perform a slight decrease and the WPU films have excellence low temperature flexibility with the increased DMPA contents. The hydrophilic property of WPU films mainly are about 80°and the tensile strength value of 7 wt% WPU reaches 45 MPa and elongation at break at 420%. [ABSTRACT FROM AUTHOR]

TiO2 catalysts were synthesized via simple sol–gel method using different carboxylic acids. The synthesized materials were characterized by UV–Vis spectroscopy (DRS), X-ray diffraction (XRD), N2 physisorption and X-ray photoelectron spectroscopy (XPS). The photocatalytic activity of the samples was evaluated in the degradation of phenol under visible and solar light. The prepared catalysts using the carboxylic acids showed an improvement in the characteristics of TiO2. Particularly, the catalyst prepared with citric acid, showed a single pure anatase phase with a small crystallite size (of around 9.4 nm), larger surface area (81 m2/g) and narrower band gap (2.94 eV) compared to the non-modified TiO2 and the reference Degussa P25. Moreover, the results showed that using citric acid, a high conversion of phenol under visible light of around 46% was achieved and a complete degradation under sunlight in a shorter time of around 90 min. [ABSTRACT FROM AUTHOR]

Silk fabrics were treated by β-cyclodextrin (β-CD) in the presence of citric acid (CA) as crosslinking agent and sodium hypophosphite (SHP) as catalyst using pad dry cure technique. CA is expected to react with β-CD and hydroxyl groups of silk fibroin via esterification reaction. Four independent factors including curing time, curing temperature, β-cyclodextrin, and citric acid concentrations were selected, and effects of these factors on the weight gain of the samples were examined. Fourier transformed infrared spectrometer (FTIR), weight gain, differential scanning calorimetry (DSC), Thermal gravimetric (TGA) and differential thermal analysis (DTA), and field-emission scanning electron microscope (FE-SEM) were employed to confirm the changes of the silk fabrics. The effect of crosslinking reaction on the color changing of samples was investigated by measurement yellowness index of the treated fabrics. The results revealed that the weight gain could reach up to 22% when fabric was treated with 50 g/L β-CD, 100 g/L CA under 170°С for 3 min. FTIR and thermal analysis demonstrated that β-CD had been grafted onto silk fabric successfully. [ABSTRACT FROM AUTHOR]

(Z)-6-(4-Chloro-5 H -1,2,3-dithiazol-5-ylidene)-4-methylcyclohexa-2,4-dien-1-one, readily prepared from 4,5-dichloro-1,3,4-dithiazolium chloride and p -cresol, reacts with benzene-1,2-diamine to give N -(2-aminophenyl)-2-hydroxy-5-methylbenzimidoyl cyanide. The latter, in acidic media, cyclizes to give, depending on the reaction conditions, 2-methylbenzofuro[2,3- b ]quinoxaline, 2-(1 H -benzo[ d ]imidazol-2-yl)-4-methylphenol or 2-(3-aminoquinoxalin-2-yl)-4-methylphenol. [ABSTRACT FROM AUTHOR]

Physicochemical properties comprising densities (ρ), speed of sound (u) and refractive indices ( n) for [EMIM]⁺[EtSO4]⁻, pentanoic acid, 2-methylpropanoic acid and binary mixtures containing {[EMIM]⁺[EtSO4]⁻ + pentanoic or 2-methylpropanoic acid} were determined across the entire mole fraction range of concentrations from 0.1 to 1.0 at T = 288.15 K to 313.15 K, under atmospheric pressure. The following thermodynamic properties: excess molar volumes ( V m E ), isentropic compressibility k s and deviation in isentropic compressibility Δ k s were computed from the measured ρ and u values. Furthermore, V m E together with Δ k s for the binary systems were negative over the entire mole fraction range at fixed temperature but increases with increasing temperature. The Redlich-Kister polynomial equation was used to correlate the derived properties with resulting values. The results obtained from this study have been discussed in terms of intermolecular interactions, H-bonding, ionic interactions and dipole moments in the binary mixtures of the ionic liquid and carboxylic acids. [ABSTRACT FROM AUTHOR]