Use Of Carboxylic Acids Research Articles

On the potential role of naturally occurring carboxylic organic acids as anti-infective agents: opportunities and challenges

Carboxylic organic acids are intermediates of central carbon metabolic pathways (e.g. acetic, propionic, citric, and lactic acid) long known to have potent antimicrobial potential, mainly at acidic pHs. The food industry has been leveraging those properties for years, using many of these acids as preservatives to inhibit the growth of pathogenic and/or spoilage fungal and bacterial species. A few of these molecules (the most prominent being acetic acid) have been used as antiseptics since Hippocratic medicine, mainly to treat infected wounds in patients with burns. With the growth of antibiotic therapy, the use of carboxylic acids (and other chemical antiseptics) in clinical settings lost relevance; however, with the continuous emergence of multi-antibiotic/antifungal resistant strains, the search for alternatives has intensified. This prospective article raises awareness of the potential of carboxylic acids to control infections in clinical settings, considering not only their previous exploitation in this context (which we overview) but also the positive experience of their safe use in food preservation. At a time of great concern with antimicrobial resistance and the slow arrival of new antimicrobial therapeutics to the market, further exploration of organic acids as anti-infective molecules may pave the way to more sustainable prophylactic and therapeutic approaches.

Rh(III)-catalysed C-H annulation of cis-stilbene acids with 2-diazo-1,3-diketones: facile access to 6,7-dihydrobenzofuran-4(5H)-one and α-pyrone scaffolds.

An efficient Rh(III)-catalysed C-H functionalization, tandem annulation of cis-stilbene acids using 2-diazo-1,3-diketones was devised. This protocol solely afforded 6,7-dihydrobenzofuran-4(5H)-ones using alicyclic diazocarbonyls via decarbonylation and α-pyrones with aliphatic diazo compounds. The chameleonic nature of cis-stilbene acid was observed with various diazo compounds by altering the additives. This synthetic method furnished good atom-economy and wide functional group tolerance, and also explained the use of carboxylic acids as a directing group. In addition, a mechanistic investigation of the catalysed reaction using ESI-MS, and the fluorescence properties of α-pyrones were well explored.

An in silico study of sustainable drug pollutants removal using carboxylic acid functionalized-MOF nanostructures (MIL-53 (Al)-(COOH)2): Towards a greener future

Emerging environmental pollutants have become a major environmental challenge due to the highly toxic effluents produced by industries. Among these emerging pollutants, pharmaceutical drugs, which are consumed and are highly soluble, lead to the severe degradation of water resources. To address this issue, adsorptive capturing methods have been considered as a potential solution due to their efficiency and environmental compatibility. This study focuses on the use of carboxylic acid functionalized MIL-53 (Al) (CA/MIL-53 (Al)) for the removal of pharmaceutical pollutants (PhPs) such as acetaminophen, ibuprofen, aspirin and methyl salicylate. The study was conducted employing quantum mechanical (QM), Monte Carlo (MC) and molecular dynamics (MD) simulations. The results of QM analysis exhibited that the functionalization of MIL-53 (Al) with carboxylic acid (CA) groups improved its adsorption affinity. Moreover, the MOF-water-Ibuprofen mixed configurations showed higher chemical reactivity and adsorption capacity. It was demonstrated that the MIL-53 (Al) adsorption characteristics were significantly improved following its functionalization with CA groups. This study highlights the potential of functionalized MOFs as a promising solution for PhPs removal from water resources. The results of this study provide valuable information for further research and the development of new adsorbents for the removal of emerging pollutants in the environment.

Principles of rational processing of red mud with the use of carboxylic acids

Due to the known limitations of economic nature, the global production complex continues to focus on the most accessible technologies of alumina production, leading to the accumulation of solid waste (red mud), which has created the well-known problem of their processing, and its scale and importance continue to grow in connection with the steady increase in the world volume of aluminum production and consumption. The priority of rational use of natural resources allows us to speak about the preference of principles of deep and waste-free processing of mineral raw materials, which are fully applicable to the processing of red mud, as accumulated raw materials of technogenic origin. At the same time, the key point of this approach becomes the hierarchical division of components into groups of technological products, taking into account the processes that ensure this selective-group division. In this regard, the use of carboxylic acids is of notable interest, as they have a known selectivity to the main components of red mud, which allows to separate low-soluble components (iron and silicon compounds) from light and rare-earth metals with minimum consumption rates. An experimental study has shown that flow-through leaching of thermochemically prepared red mud using formic acid provides high and acceptable recoveries of sodium, calcium, scandium, and rare earth metals. This makes it affordable to use the cheapest method of apparatus-free leaching when implementing this approach on an industrial scale. Experimentally determined the differences in the sequence of elution of sodium, calcium, aluminum and rare-earth metals formates during flow leaching, which creates favorable conditions for concentrating components and separate processing of sampled solutions. The regime parameters of the process that provides complete precipitation of aluminum, scandium and rare earth metals during the neutralization of formate solution with milk of lime, resulting in the necessary prerequisites for further concentration of rare earth metals to obtain technologically significant product are determined. The work was carried out with the financial support of the Russian Science Foundation under the Agreement No. 18-19-00577-П of April 28 2021 of grant for fundamental scientific research and exploratory scientific research.

Carboxylic acid catalysis on the imine formation versus aza‐Michael reaction in apolar aprotic solvent

AbstractThe reaction between primary amine and α,β‐unsaturated aldehydes and ketones can produce α,β‐unsaturated imines or aza‐Michael products. However, a theoretical reaction mechanism with the corresponding free energy profile compatible with experimental kinetics in aprotic apolar solvents has not been reported yet. In this work, we have used theoretical calculations to investigate the mechanism behind the 1,2‐addition and 1,4‐addition of benzylamine (BnNH2) to methyl vinyl ketone (MVK) in toluene solution. The calculation of the free energy profile was followed by a microkinetic analysis. According to our results, the experimentally observed formation of the aza‐Michael product is due to more favorable kinetics of the nucleophilic attack of the BnNH2 to the β‐carbon of s‐cis conformation of MVK. Furthermore, acetic acid can be present in MVK as a stabilizer. This contaminant catalyzes the transfer of protons for the formation of the aza‐Michael product and can also catalyze the imine formation. The present analysis indicates that catalysts for proton transfer are essential for the reaction to proceed in aprotic solvent and explain the use of carboxylic acids as an additive in aza‐Michael reactions. In the case of acetic acid, this species has a powerful catalytic effect, which explains why even a trace amount is enough for catalysis. A higher concentration of acetic acid could in principle favor the imine mechanism. However, a high concentration of acetic acid leads to the dimerization of this species, producing a low concentration of the free acid and limiting its ability to produce competitive kinetics for imine formation.

Decarboxylative Claisen Condensations with Substituted Malonic Acid Half Oxyesters

AbstractA decarboxylative Claisen condensation involving substituted malonic acid half oxyesters (SMAHOs) as pronucleophiles has been developed. The addition of their magnesium enolates to various acyl donors allows the synthesis of functionalized α-substituted β-keto esters in moderate to excellent yields (13–96%). In addition to acyl chlorides and acid anhydrides, these conditions proved efficient for the use of carboxylic acids as acylating agents, thus allowing to greatly extend the scope of this transformation (32 examples overall).

<sup>29</sup>Si NMR Investigation of the Effect of Acetic and Oxalic Acids on Portland-Limestone Cement Hydration

The use of carboxylic acids in mix design alters the hydration process of cement, the resulting pore structure of the obtained cement paste, and, consequently, the mechanical properties of concrete. All these changes are directly related to the structure of the calcium silicate hydrate phase. In the present study, the effect of acetic acid and oxalic acid on the hydration of Portland-limestone cement was monitored using solid state 29Si NMR spectroscopy. The results showed that acetic acid facilitated alite and belite hydration, however, the formation of polymerized silicate chains, incorporating Q2p species, begun later than in pure cement paste. Oxalic acid accelerated the polymerization, but slowed down alite and belite hydration. Such behaviors may correspond to decreased porosity (acetic acid addition) and increased strength (oxalic acid addition). Both acids accelerated belite hydration, compared to the pure paste, likely due to an increased acidity of the pore solution. The findings provide structural information about C─S─H phase, to be considered for thaumasite sulfate attack investigations on Portland-limestone cement pastes containing carboxylic acids.

Evaluation of deep eutectic solvent pretreatment towards efficacy of enzymatic saccharification using multivariate analysis techniques

In this paper, deep eutectic solvent (DES) pretreatment of lignocellulosic biomass was analysed using principal component analysis (PCA) and partial least square (PLS) methods to determine correlations between the pretreatment process variables and assess their significance level. The analysis was conducted on the dataset containing 103 experimental observations and 32 variables. Both PCA and selected PLS model (M4) had substantial prediction power and prediction relevance, as exhibited by their good cumulative explained variance (R2cum, 0.787) and cumulative predicted variance (Q2cum, 0.524) for six principal components of PCA model, and explained variance of independent variable (R2Xcum, 0.781), explained variance of dependent variable (R2Ycum, 0.803) and cumulative predicted variance (Q2cum, 0.776) for the best PLS model. The results of PCA and PLS analyses revealed that the most significant variables for DES pretreatment were severity factor , temperature, type of antisolvent, particle size, agitation intensity and type of hydrogen bond donor (HBD) of the DES. The use of carboxylic acid and hydroxy acid HBD was associated with higher glucose yield and shorter duration of saccharification . The models also showed that enzymatic saccharification was more efficient when organic solvent or inorganic salt solution was used as antisolvent for lignocellulose regeneration. Usage of water as antisolvent was associated with reduced glucose yield during saccharification. Another notable outcome of this work was that intensive stirring during pretreatment had negative effect on glucose yield due to the shear thickening properties of DESs. This work provided a systematic analysis of DES pretreatment process of lignocellulosic biomass using PCA and PLS methods that allowed better understanding of the factors affecting the pretreatment process. • Multivariate analysis of PCA and PLS were used to study DES pretreatment. • The models had high predictive accuracy with good R2Xcum, R2Ycum, Q2cum values. • SF, antisolvent, particle size, agitation and HBD had great impact on pretreatment. • Long p-time, low t, AS (organic, inorganic), HBD (–COOH, –OH) favored pretreatment. • High agitation intensity and large particle size led to poor pretreatment.

Exploiting the sp2 character of bicyclo[1.1.1]pentyl radicals in the transition-metal-free multi-component difunctionalization of [1.1.1]propellane.

Strained bicyclic substructures are increasingly relevant in medicinal chemistry discovery research because of their role as bioisosteres. Over the last decade, the successful use of bicyclo[1.1.1]pentane (BCP) as a para-disubstituted benzene replacement has made it a highly valuable pharmacophore. However, various challenges, including limited and lengthy access to useful BCP building blocks, are hampering early discovery research. Here we report a single-step transition-metal-free multi-component approach to synthetically versatile BCP boronates. Radicals derived from commonly available carboxylic acids and organohalides perform additions onto [1.1.1]propellane to afford BCP radicals, which then engage in polarity-matched borylation. A wide array of alkyl-, aryl- and alkenyl-functionalized BCP boronates were easily prepared. Late-stage functionalization performed on natural products and approved drugs proceeded with good efficiency to generate the corresponding BCP conjugates. Various photoredox transformations forging C-C and C-N bonds were demonstrated by taking advantage of BCP trifluoroborate salts derived from the BCP boronates.

Carbene and photocatalyst-catalyzed decarboxylative radical coupling of carboxylic acids and acyl imidazoles to form ketones

The carbene and photocatalyst co-catalyzed radical coupling of acyl electrophile and a radical precursor is emerging as attractive method for ketone synthesis. However, previous reports mainly limited to prefunctionalized radical precursors and two-component coupling. Herein, an N-heterocyclic carbene and photocatalyst catalyzed decarboxylative radical coupling of carboxylic acids and acyl imidazoles is disclosed, in which the carboxylic acids are directly used as radical precursors. The acyl imidazoles could also be generated in situ by reaction of a carboxylic acid with CDI thus furnishing a formally decarboxylative coupling of two carboxylic acids. In addition, the reaction is successfully extended to three-component coupling by using alkene as a third coupling partner via a radical relay process. The mild conditions, operational simplicity, and use of carboxylic acids as the reacting partners make our method a powerful strategy for construction of complex ketones from readily available starting materials, and late-stage modification of natural products and medicines.

Surface Modification of PVDF Membrane Using Formic Acid for Enhance the Hydrophobicity for Desalination

Membrane distillation (MD) is a thermally driven membrane separation process. In recent years, MD is considered as a key technology for desalination applications. It has been proven that it has numerous advantages compared to other desalination processes such as reverse osmosis. The thermal driving force, no osmotic pressure effect on membrane fluxes are among the advantages of this MD process. Membranes fabricated from hydrophobic polymers such as polyvinylidene fluoride (PVDF) can be a great choice for MD for the desalination process. However, MD membranes are still held back by some problems, most notably due to pore wetting effects, thereby limiting their use in treating seawater for desalination propose. This study proposes the use of carboxylic acid to modify the PVDF membrane to increase its hydrophobicity as a solution to avoid wetting in MD for water desalination. As a first step, membrane produced using PVDF pellets under the phase inversion method. Then the membrane underwent modification using 5wt%, 10wt% and 15wt% of formic acid via immersion technique. The characteristics of membrane produced observed by the contact angle, Fourier-transform infrared spectroscopy (FTIR) and membrane performance test. The impact of the concentration of formic acid solution and feed temperature on the membrane was evaluated. The result showed that by modifying the membrane with formic acid resulted in the increase in contact angle from unmodified PVDF membrane, 83.03° to 100.88° when the membrane modified with formic acid with concentration was 10 wt%. It was subsequently shown through FTIR peaks that formic acid successfully modified the PVDF membranes. Highest salt rejection percentage was also obtained with 68.9% when the feed temperature is 60 °C.

Recovery of platinum group metals from spent automotive converters by leaching with organic and inorganic acids and extraction with quaternary phosphonium salts

The paper presents studies on the application of hydrometallurgical recovery of platinum group metals (PGM) from spent automotive converters (SAC), which is not only commercially viable but also important from an ecological perspective. The work proposes an integrated four-stage process, which includes: leaching with oxalic or lactic acids, then leaching with mineral acids from catalyst left after the first stage and next extraction of PGM with phosphonium or ammonium salts: Cyphos IL 101 (trihexyl(tetradecyl)phosphonium chloride), Cyphos IL 104 (trihexyl(tetradecyl)phosphonium bis(2,4,4-trimethylpentyl)phosphinate), and in the final stage, stripping with 0.1 M thiourea in 0.5 M HCl and 3 M HNO3 to recover PGM. The use of carboxylic acids in the first step of leaching reduces the amount of non-precious metals (Fe ions, Mg(II), Zn(II)) leached in the second stage. The highest concentration of the leached Al(III), Fe ions, Mg(II) and Zn(II) was 600, 25, 110 and 45 mg/dm3. To leach PGM from SAC, it was necessary to use stronger acidic solutions (e.g. a mixture of inorganic acids with an oxidant). The concentrations of Pt(IV), Pd(II), Rh(III) in the solutions after the second step of leaching were 34–40, about 3, 4.5–5 mg/dm3, respectively. After two stages of extraction, Rh(III) and Al(III) are left in the raffinate, therefore Pt(IV) and Pd(II) can be separated from Rh(III). Afterward, Pd(II) and Pt(IV) extracted to the organic phases can be separated in the first stage of stripping.

Decarboxylation‐Initiated Intermolecular Carbon‐Heteroatom Bond Formation

AbstractCarboxylic acids are among the most used feedstock chemicals due to their great structural diversity and easy handling. The use of carboxylic acids and their derivatives in decarboxylative couplings has proven to be a valuable tool for the construction of C−C and C‐heteroatom bonds. This synthetic strategy provides a complementary bond disconnection to traditional cross‐coupling methods. In this review, we provide a comprehensive overview of decarboxylation‐initiated intermolecular C‐heteroatom bond formation, outlining several main mechanistic concepts combined with early examples and highlighting the achievements made in the past decade until January 2021. In these reactions, carboxylic acids and their derivatives undergo initial decarboxylation and then react with other heteroatom electrophiles and nucleophiles, thus replacing the carboxylate group with a valuable and prevalent heteroatom functionality.magnified image

Immunoassay-Amplified Responses Using a Functionalized MoS2-Based SPR Biosensor to Detect PAPP-A2 in Maternal Serum Samples to Screen for Fetal Down's Syndrome.

BackgroundDue to educational, social and economic reasons, more and more women are delaying childbirth. However, advanced maternal age is associated with several adverse pregnancy outcomes, and in particular a high risk of Down’s syndrome (DS). Hence, it is increasingly important to be able to detect fetal Down’s syndrome (FDS).MethodsWe developed an effective, highly sensitive, surface plasmon resonance (SPR) biosensor with biochemically amplified responses using carboxyl-molybdenum disulfide (MoS2) film. The use of carboxylic acid as a surface modifier of MoS2 promoted dispersion and formed specific three-dimensional coordination sites. The carboxylic acid immobilized unmodified antibodies in a way that enhanced the bioaffinity of MoS2 and preserved biorecognition properties of the SPR sensor surface. Complete antigen pregnancy-associated plasma protein-A2 (PAPP-A2) conjugated with the carboxyl-MoS2-modified gold chip to amplify the signal and improve detection sensitivity. This heterostructure interface had a high work function, and thus improved the efficiency of the electric field energy of the surface plasmon. These results provide evidence that the interface electric field improved performance of the SPR biosensor.ResultsThe carboxyl-MoS2-based SPR biosensor was used successfully to evaluate PAPP-A2 level for fetal Down’s syndrome screening in maternal serum samples. The detection limit was 0.05 pg/mL, and the linear working range was 0.1 to 1100 pg/mL. The women with an SPR angle >46.57 m° were more closely associated with fetal Down’s syndrome. Once optimized for serum Down’s syndrome screening, an average recovery of 95.2% and relative standard deviation of 8.5% were obtained. Our findings suggest that carboxyl-MoS2-based SPR technology may have advantages over conventional ELISA in certain situations.ConclusionCarboxyl-MoS2-based SPR biosensors can be used as a new diagnostic technology to respond to the increasing need for fetal Down’s syndrome screening in maternal serum samples. Our results demonstrated that the carboxyl-MoS2-based SPR biosensor was capable of determining PAPP-A2 levels with acceptable accuracy and recovery. We hope that this technology will be investigated in diverse clinical trials and in real case applications for screening and early diagnosis in the future.

Investigation of The Reaction Kinetics of Chromium(III) Ions with Carboxylic Acids In Aqueous Solutions and The Associated Effects on Chromium Deposition

Electroplated chromium is an important industrial coating. Both in the decorative and functional field, research is being carried out to develop trivalent chromium electrolytes. In this work, the interaction between CrIII ions and carboxylic acids (malonic acid, malic acid, oxalic acid and glycolic acid) is investigated. The use of carboxylic acids to improve the current efficiency in trivalent chromium plating baths has been known for a long time. But the thermodynamics and kinetics of the associated complexing reactions are not well understood. It is shown that the complexes form at different rates depending on the acid and its concentration and have a varying influence on chromium deposition. For the development of a technical bath, care must be taken to ensure that the molar ratios between chromium and carboxylic acids can be controlled. This is possible with the HPLC method presented here.

Burning season and vegetation coverage influenced the community-level physiological profile of Mediterranean mixed-mesogean pine forest soils

Knowledge of forest soil ecology is necessary to assess vulnerability to disturbances, such as wildfires, and improve its microbial diversity and functional value. Soil microbiota play an important role in forest soil processes and are a key driver of postfire recovery, but they are very vulnerable to heat. According to future scenarios for climate and land-use change, fire regimes will undergo transformations in semiarid terrestrial ecosystems, mainly in the Mediterranean Basin. To develop tools for forest management in fire-prone areas, i.e., fire prevention, we assessed the impact of prescribed burnings on soil microorganisms in Mediterranean mixed pine forests. We hypothesised that low severity fire burns would not influence the functional diversity of soil microorganisms, although the burning season could influence that response due to seasonal variations in its vulnerability. We used the Biolog EcoPlate System to record soil biological indicators and assess the effect of the prescribed burning season (early or late season) on bacterial communities, including the soil–plant interphase. The soil microbiome response differed significantly according to vegetation coverage but prescribed burning season was not directly related. Burning increased the proportions of soil organic matter and soil organic carbon, and also promoted cation-exchange capacity and total phosphorus, which were higher following spring burns. Microbial richness and the Shannon–Weaver diversity index both showed a positive correlation with vegetation cover. However, microbial richness was triggered after burning uncovered patches of vegetation. We also noted differences in the usage pattern for the six substrate groups defined in our study: the use of carboxylic acids, amino acids and carbohydrates was higher in unburned plots and those subject to late burns, whereas amino acids did not predominate in early burn plots.

Effect of Azamethiphos on enzymatic activity and metabolic fingerprints of marine microbial communities from the water column

Salmon production in Chile has increased significantly since the 1990s. However, there have been significant economic losses owing to outbreaks of Caligus rogercresseyi. Pesticides, among them Azamethiphos, are used to mitigate the impact of this sea louse. Azamethiphos can affect non-target species living near salmon farms such as microbial plankton, although there is little information about this. The general objective of this study was to determine the effect of different concentrations of the pesticide Azamethiphos on the metabolism of microbial plankton communities (<100 μm) in two contrasting zones, one without salmon farming and the other with a high level of aquaculture activity. Several methodological approaches were used, including the enzymatic activity of β-glucosidase and malate dehydrogenase (MDH), fingerprinting techniques (EcoPlates for bacteria and FF microplate for marine fungi) and the estimation of microbial aerobic respiration. We found greater degradation of the pesticide Azamethiphos in the salmon culture zone (~72.4%) than in an area not previously used in salmon production (~26.1%). The response of microbial β-glucosidase activity to Azamethiphos is highly variable, but there is a tendency toward more activity in the smaller size fractions (5–25 μm and 0.22–3 μm) when exposed to high Azamethiphos concentrations. We also detected a highly variable response in microbial MDH activity. The most widely used carbon substrates by bacterioplankton and marine fungi are those related to carbohydrate metabolism. We also found increased use of carboxylic acids and amino acids in the treatments with higher concentrations of Azamethiphos. Enzyme activity, together with metabolic fingerprints, could be used as an indicator of perturbations in marine microbial communities.

Polysulfone membranes with CNTs/Chitosan biopolymer nanocomposite as selective layer for remarkable heavy metal ions rejection capacity

Chitosan (CHIT) biopolymer has a remarkable adsorption capacity for heavy metal ions. The incorporation of multiwall carbon nanotubes (CNTs) into the CHIT matrix should enhance the water permeability and separation performance of the CHIT. The use of carboxylic acid functionalised multiwall carbon nanotubes (CNTS-COOH) as an additive is aimed at adding the COOH functional group to the CHIT matrix without blocking its adsorption sites. Therefore, two nanocomposites CNTs-COOH/CHIT and CNTs/CHIT are used as a selective layer on top of polysulfone (PS) to form CNTs-COOH/CHIT/PS and CNTs/CHIT/PS membranes. To the best of our knowledge, the efficiency of the CNTs-COOH/CHIT nanocomposite as a selective layer on polysulfone sheet to enhance the membrane’s rejection for metal ions is reported for the first time. Both fabricated membranes are investigated in terms of morphology, wettability, surface charge, porosity and water permeability. CNTs-COOH/CHIT/PS membrane recorded water flux rate 64.4 L m−2 h−1 at transmembrane pressure 22 bar, where CNTs/CHIT/PS membrane recorded 57.15 L m−2 h−1 at transmembrane pressure 22 bar. Heavy metal ions rejection capabilities of both membranes are evaluated at various pHs and transmembrane pressures. Both CNTs-COOH/CHIT/PS and CNTs/CHIT/PS membranes effectively reject Cu+2, Ni+2, Pb+2, Cd+2, and Co+2 ions from aqueous solutions. At pH 3, CNTs-COOH/CHIT/PS and CNTs/CHIT/PS membranes presented significant rejection ranged 71–92.2% for examined metal ions. Where at pH range (6–8), Co+2 rejection reached up to 92.2% and 89.6% by CNTs /CHIT/PS and CNTs-COOH/CHIT/PS membranes, respectively. Overall, the CNTs-COOH/CHIT/PS membrane shows metal ions rejection superior to that of the CNTs/CHIT/PS membrane.

Biochar and compost as gentle remediation options for the recovery of trace elements-contaminated soils

The use of organic-based amendments for gentle remediation options (GRO), i.e. the stabilization of trace elements (TE) in polluted soils and the reduction of their impact on soil microbial and biochemical features, has been constantly growing in last 10 years. To verify the effectiveness of biochar and compost in such context, biochar (1 and 3% w/w), compost (3% w/w) and their combination (compost 2% + biochar 2% w/w) were added to two sub-alkaline soils (FS and MS) contaminated with Sb (41–99 mg kg−1 respectively), As (~18 mg kg−1), and trace metals such as Ni (103–172 mg kg−1 respectively) and Cr (165–132 mg kg−1 respectively). Most of the treatments (especially 3% biochar) reduced labile TE pools (water-soluble and exchangeable) and increased their residual (non-extractable) fractions (e.g. +48, 56, 66, and 68% of residual Sb, As, Cr and Ni in MS-treated soil compared to the untreated control). The amendments addition had both stimulating and inhibiting effects on the activity of soil microbial communities, as shown by the Biolog community level physiological profiles. However, in both soils, 3% biochar produced the highest increase of metabolic potential as well as the use of carboxylic acids and polymers by the soil microbial communities. Likewise, soil dehydrogenase (DHG), β-glucosidase (β-GLU) and urease (URE) activities were significantly enhanced in FS and MS soils treated with 3% biochar (e.g. +77, 48, and 17% for DHG, URE and β-GLU in FS-3% biochar with respect to untreated FS). Overall, the results from this study showed that the amendments investigated (particularly 3% biochar) can be effectively used for GRO of sub-alkaline soils, being able to reduce labile TE and to increase the metabolic potential and actual biochemical activities of the respective soil microbial communities. The manifold environmental implications of such effects are discussed.

Direct Use of Carboxylic Acids in the Photocatalytic Hydroacylation of Styrenes To Generate Dialkyl Ketones.

A general protocol for the hydroacylation of styrenes from aliphatic carboxylic acids is reported. These reactions proceed via β-scission of a phosphoranyl radical that is accessed by photoredox catalysis, followed by addition of the resulting acyl radical to the styrenyl olefin. We show that phosphine tunability is critical for efficient intermolecular coupling due to competitive quenching of the photocatalyst by the olefin. Primary, secondary, and structurally rigid tertiary carboxylic acids all generate valuable unsymmetrical dialkyl ketones.