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The quest for sustainable synthesis of carboxylic acids has led to the exploration of innovative routes and catalysts for the oxidative cleavage of carbon−carbon double bonds, prevalent in bio‐derived molecules. This process involves multiple steps including epoxidation, hydrolysis and vicinal diol cleavage, often catalysed by unsustainable homogeneous or noble‐metal catalysts. In this study, we present the utilization of Fe‐ZSM‐5 as a versatile bifunctional catalyst capable of catalysing both hydrolysis and vicinal diol cleavage steps, utilizing propylene oxide as model compound and H2O2 as oxidizing agent. The prepared Fe‐ZSM‐5 features the zeolite intrinsic Lewis and Brønsted acidity functions, essential for the hydrolysis step, as well as high fractions of monomeric FeOx species, crucial for the subsequent vicinal diol cleavage, leading to streamlined carboxylic acids formation in a one‐pot, two‐step process. Moreover, by combining Fe‐ZSM‐5 with TS‐1, renowned for its epoxidation activity, we demonstrate the complete cascade reaction in one pot, under mild conditions, starting from ethylene. Our study expands the utility of cost‐effective zeolite‐based catalysts enriched with abundant Fe metal for the one‐pot oxidative cleavage of C=C double bonds, offering a promising pathway towards sustainable carboxylic acid synthesis. [ABSTRACT FROM AUTHOR]

5‐Hydroxymethylfurfural (5‐HMF) is an important biomass‐based platform compound that links biomass feedstocks with petrochemical refinery products. In this work, we developed a novel approach using triethylbenzylammonium chloride (TEBAC)‐based acidic deep eutectic solvents (ADESs) to synthesize 5‐HMF through the dehydration of fructose. Our approach demonstrates significant improvements in both 5‐HMF yield and process efficiency compared to conventional solvent systems. Under optimal experimental conditions (90 °C, 4.5 h), a maximum 5‐HMF yield of 97.77±3.20 % was achieved at a TEBAC:acetic acid ratio of 2 : 3 with 1 wt % fructose loading, which represents a notable advancement over other methods. Notably, our system inhibits the formation of by‐products such as levulinic acid (LA) and formic acid (FA), which are commonly detected in other dehydration processes. Additionally, higher 5‐HMF yields of 76.67±0.33 % and 73.51±1.14 % were achieved with 10 wt % and 20 wt % fructose loadings, respectively, further highlighting the scalability of the process. The acidity of ADESs was found to significantly affect the dehydration rate and yield, as demonstrated through Hammett's acidity function analysis. The key innovation of our study lies in the strategic selection of hydrogen bond donors and acceptors in the DES, enabling both high efficiency and selectivity in 5‐HMF production. These findings provide a promising pathway for large‐scale biomass conversion with reduced by‐product formation. [ABSTRACT FROM AUTHOR]

The self-cleaning effect of titanium dioxide coatings is based on the photocatalytic oxidative ability and the phenomenon of photoinduced superhydrophilicity. Doping with metals is used to enhance the photocatalytic activity; however, its influence on the surface hydrophilicity remains to be studied. In this work, the effect of the heterovalent doping of titanium dioxide anatase on its hydrophilic properties has been investigated in detail. Thin xM–TiO2 films, where the M symbol denotes Nb5+, Sc3+, and Al3+, with dopant concentrations of 0.0–1.0 at % have been obtained on glass substrates from solutions of corresponding sols by the deep coating method. The phase composition, surface dopant content, lattice microstress, surface acidity, and electron work function values have been determined and analyzed for three series of doped samples as functions of dopant concentrations. The surface hydrophilicity of xM–TiO2 nanocoatings has been estimated by measuring water contact angle and surface free energy values. It has been shown that doping with niobium ions affects the wettability of titanium dioxide, while its hydrophilic state remains unchanged upon doping with scandium and aluminum ions. It has been found that the incorporation of niobium ions into anatase drastically increases the hydrophilicity of the surface with a simultaneous change in its acidity and work function. At the same time, as Nb content increases, the electronic factor prevails. The kinetic dependences obtained for the photoinduced water contact angles have shown an increase in the surface hydrophilicity of all investigated coatings irrespective of a dopant type within the studied dopant concentration range, thereby indicating their self-cleaning ability. At the same time, the final UV-induced hydrophilic state depends on a dopant type. The maximum surface hydrophilicity is achieved upon UV irradiation of TiO2 doped with Nb regardless of its content. UV-irradiated Al-doped TiO2 coatings exhibit small contact angles, while the photoinduced surface hydrophilicity of Sc-doped titanium dioxide films decreases with increasing scandium concentration. [ABSTRACT FROM AUTHOR]

The conditions for the smart colorimetric determination of cetylpyridinium chloride and sodium dodecyl sulfate by reaction with Coomassie brilliant blue G (CBBG) have been proposed. The nature of the absorption and fluorescence spectra of aqueous solutions of CBBG as a function of acidity has been investigated. A variety of reagent forms and associations with ionic surfactants have been demonstrated. The composition of the associates formed in the CBBG–cationic surfactant system has been established. The increase in the analytical signal of the cationic surfactant and the stabilization of the colloid-chemical state of the system during reactions in the organized medium of the nonionic surfactant Triton X-100 has been demonstrated. These effects are realized through association in premicellar solutions and as a result of the solubilization of components in Triton X-100 micellar solutions. The addition of long-chain cationic surfactants to the reagent occurs with the replacement of the heteroatom proton. The absorption of CBBG–cationic surfactant associates solutions increases with the length of the cationic surfactant hydrocarbon chain. Ethanol additives decrease the aggregation of CBBG. The technique of cationic surfactant determination has been tested in the analysis of the pharmaceutical. The results show that the simplicity of analytical signal registration with satisfactory correctness and acceptably high sensitivity of determination is an advantage of the developed technique. [ABSTRACT FROM AUTHOR]

Although bismuth is a low toxic metal compared to other heavy metals, but its continuous accumulation in living tissues is considered a serious issue for health and environment. The present investigation aims to test the adsorption technique for removing bismuth ions from polluted aqueous medium via pomegranate peels as low-cost medium in an adsorption unit of batch-type at various operating parameters. The obtained results showed that pomegranate peels have a remarkable efficiency in to recover Bi+3 ions from polluted water, reaching approximately 75% at 38 ppm initial bismuth concentration, agitation speed of 350 rpm, 2.4 h contact time, acidity function of 7.5 g dose of pomegranate peel, and 20 °C temperature. Isothermal and kinetic studies indicated that the Langmuir and pseudo-second order models are the closest to describing the adsorption. Furthermore, the adsorption was spontaneous, physical, and of low entropy according to thermodynamic, while the adsorption capacity was 2.26 mg/g. In order to dispose of the residual waste in an environmentally safe manner, it was investigated to convert them into a rodenticide. The pomegranate peels loaded with bismuth ions showed a clear and effective effect against laboratory rats of Sprague Dawley type, and the lethal half dose (LD50) calculated was very close to what was mentioned in the literature. [ABSTRACT FROM AUTHOR]

A number of phosphomolybdic acid dispersed on SBA-15 catalysts with structural defects and strong acidity were synthesized and applied for the production of ultralow sulfur diesel. The oxygen defect concentration in the catalysts was quantitatively determined by the Rietveld refinement method. These catalysts contained many Brønsted (B) and Lewis (L) acid sites (648 to 1479 μmol g−1) depending on the heteropolyacid content and the thermal treatment. The Mo5+/Mo6+ ratio calculated by XPS technique varied from 0.21 to 0.27%, indicating the creation of oxygen defects in the Keggin unit. The area under the IR absorption band at 980 cm−1 (characteristic of the Mo＝O bond) in the FTIR spectra of different catalysts was found to be inversely proportional to the variation of L acidity as a function of temperature, indicating that oxygen defects are the origin of the L acidity. In the oxidation reaction for removing dibenzothiophene, DBT, from a model diesel, the DBT conversion correlated well with the oxygen defect concentration and total surface acidity, confirming that the surface acidity and oxygen defects played key roles in DBT adsorption and oxidation. Almost 100% DBT conversion was achieved on the best 30 wt% H3PMo12O40/SBA-15 catalyst under the optimal reaction conditions (reaction time 60 min, reaction temperature 70 °C, H2O2/DBT molar ratio 6–8, catalyst concentration 2–2.5 mg ml−1, and hydrogen peroxide to formic acid molar ratio 1.5). A novel mechanism of the DBT oxidative removal in a biphasic system involving the participation of the neighboring L and B acid sites, oxygen defects, and the formation of peroxometallic and superoxometallic species was proposed. [ABSTRACT FROM AUTHOR]

Investigating proton transport at the interface in an excited state facilitates the mechanistic investigation and utilization of nanomaterials. However, there is a lack of suitable tools for in-situ and interfacial analysis. Here we addresses this gap by in-situ observing the proton transport of graphene quantum dots (GQDs) in an excited state through reduction of magnetic resonance relaxation time. Experimental results, utilizing 0.1 mT ultra-low-field nuclear magnetic resonance relaxometry compatible with a light source, reveal the light-induced proton dissociation and acidity of GQDs' microenvironment in the excited state (Hammett acidity function: –13.40). Theoretical calculations demonstrate significant acidity enhancement in –OH functionalized GQDs with light induction (p K a * = –4.62, stronger than that of H2SO4). Simulations highlight the contributions of edge and phenolic –OH groups to proton dissociation. The light-induced superacidic microenvironment of GQDs benefits functionalization and improves the catalytic performances of GQDs. Importantly, this work advances the understanding of interfacial properties of light-induced sp2–sp3 carbon nanostructure and provides a valuable tool for exploring catalyst interfaces in photocatalysis. Understanding interfacial proton transport in an excited state is crucial for catalytic and diagnostic applications of nanomaterials. Here, the authors combine ultra-low-field NMR relaxometry with a light source to study the light-induced proton dissociation of graphene quantum dots. [ABSTRACT FROM AUTHOR]

The tumor microenvironment is increasingly acknowledged as a critical contributor to cancer progression, mediating genetic and epigenetic alterations. Beyond diverse cellular interactions from the microenvironment, physicochemical factors such as tumor acidosis also significantly affect cancer dynamics. Recent research has highlighted that tumor acidosis facilitates invasion, immune escape, metastasis, and resistance to therapies. Thus, noninvasive measurement of tumor acidity and the development of targeted interventions represent promising strategies in oncology. Techniques like contrast-enhanced ultrasound (CEUS) can effectively assess blood perfusion, while ultrasound-stimulated microbubble cavitation (USMC) has proven to enhance tumor blood perfusion. We therefore aimed to determine whether CEUS assesses tumor acidity and whether USMC treatment can modulate tumor acidity. Firstly, we tracked CEUS perfusion parameters in MCF7 tumor models and compared them with in vivo tumor pH recorded by pH microsensors. We found that the peak intensity and area under curve of tumor contrast-enhanced ultrasound correlated well with tumor pH. We further conducted USMC treatment on MCF7 tumor-bearing mice, tracked changes of tumor blood perfusion and tumor pH in different perfusion regions before and after the USMC treatment to assess its impact on tumor acidity and optimize therapeutic ultrasound pressure. We discovered that USMC with 1.0 Mpa significantly improved tumor blood perfusion and tumor pH. Furthermore, tumor vascular pathology and PGI2 assays indicated that improved tumor perfusion was mainly due to vasodilation rather than angiogenesis. More importantly, analysis of glycolysis-related metabolites and enzymes demonstrated USMC treatment can reduce tumor acidity by reducing tumor glycolysis. These findings support that CEUS may serve as a potential biomarker to assess tumor acidity and USMC is a promising therapeutic modality for reducing tumor acidosis. [ABSTRACT FROM AUTHOR]

Background: Elettaria cardamomum possesses a variety of beneficial effects. Thus, we aimed to investigate cardamom essential oilloaded nanostructured lipid carrier (CEO-NLC) gastro-protective effects in an ethanol-induced gastric ulcer in a rat model. Materials and Methods: Forty male albino rats of the Wistar strain were assigned into eight groups. Pretreatment of animal groups with the low (300 mg/kg) and high (600 mg/kg) doses of CEO-NLC alleviates the pathological damage. It significantly reduces the ulcer areas induced by ethanol in rats, reducing pH, gastric-free, and total acidity measurements. Omeprazole 20 mg/kg was utilized as a reference medication to compare its effect with CEO-NLC. Results: Treatment with CEO-NLC increases total antioxidant capacity and suppresses oxidative damage of the stomach by lowering malonaldehyde (MDA) levels. Furthermore, inflammatory infiltration in groups treated with CEO-NLC is alleviated by decreasing the release of pro-inflammatory cytokines, including IL-6 and TNF-α and increasing anti-inflammatory IL-10. Administration of CEO-NLC, either at prophylactic or therapeutic doses, significantly reduces gastrin levels. Conclusion: CEO-NLCs demonstrated curative effects in inhibiting ethanolinduced gastric damage, which is related to suppressing gastric inflammation and oxidative stress. Thus, CEO-NLC might enhance the management of gastric ulcers. [ABSTRACT FROM AUTHOR]

Viili, a Finnish ropy fermented milk, is traditionally manufactured through spontaneous fermentation, by mesophilic lactic acid bacteria and yeast-like fungi, or back-slopping. This study evaluated four natural viili starters as sources of lactic acid bacteria for dairy production. Back-slopping activation of the studied viili samples was monitored through pH and titratable acidity measurements and enumeration of mesophilic lactic acid bacteria. Sixty lactic acid bacteria isolates were collected, molecularly identified, and assayed for acidification performance, enzymatic activities, production of exopolysaccharides (EPSs), presence of the histidine decarboxylase (hdcA) gene of Gram-positive bacteria, and production of bacteriocins. A neat predominance of Lactococcus lactis emerged among the isolates, followed by Enterococcus faecalis, Enterococcus faecium, Enterococcus durans, Enterococcus lactis, and Lactococcus cremoris. Most isolates exhibited proteolytic activity, whereas only a few enterococci showed lipase activity. Five isolates identified as L. cremoris, L. lactis, and E. faecalis showed a good acidification performance. Most of the isolates tested positive for leucine arylamidase, whereas only one E. durans and two L. lactis isolates were positive for valine arylamidase. A few isolates also showed a positive reaction for beta-galactosidase and alpha- and beta-glucosidase. None of the isolates produced EPSs or bacteriocins. The hdcA gene was detected in five isolates identified as L. lactis and E. faecium. A few L. cremoris and L. lactis isolates for potential use as starter or adjunct cultures for dairy processing were finally identified. [ABSTRACT FROM AUTHOR]

Soil exchangeable acidity (EA) is an indicator of aluminium toxicity potential in acidic soils. Predicting the distribution and dynamics of EA is needed for the identification and management of acidic soils. In this study, we used datasets of 355 pedons from across Ghana and the Cubist rule‐based algorithm to generate pedotransfer functions (PTFs) of EA. Eight soil properties (pH, organic carbon, calcium, sodium, magnesium, total exchangeable bases, cation exchange capacity [CEC] to clay ratio and soil depth) were used to predict EA. We first used the whole dataset to construct generic PTFs and then stratified the dataset based on World Reference Base‐Reference Soil Groups (WRB‐RSGs) to generate soil‐specific PTFs. Goodness‐of‐fit statistics comprising the root mean squared error (RMSE), Lin's concordance correlation coefficient (ρC$$ {\rho}_C $$) and coefficient of determination (R2) were used to evaluate the prediction accuracy and reliability of the developed PTF models on both calibration and validation datasets. The Fluvisols EA‐PTF exhibited lower performance metrics in the validation (RMSE = 0.17 cmolc kg−1, ρC$$ {\rho}_C $$ = 0.19, R2 = 0.24), whereas the EA‐PTFs for all other WRB‐RSGs and whole dataset had above‐average performance metrics in the validation (0.05 ≤ RMSE ≤ 0.97 cmolc kg−1; 0.34 ≤ ρC$$ {\rho}_C $$ ≤ 0.94; 0.52 ≤ R2 ≤ 0.96). Soil pH sufficed for predicting EA in soils with pH above 5.0, but in soils with a pH < 5.0, the levels of exchangeable bases (e.g., Na+, K+, Mg2+, Ca2+), CEC to clay ratio (CCR) and soil depth improved the prediction of EA. The developed EA‐PTFs are useful for estimating the missing values of EA in soil databases. [ABSTRACT FROM AUTHOR]

Monofunctional Pt(II) complexes with potent efficacy to overcome the drawbacks of current platinum drugs represent a promising therapeutic approach for triple negative breast cancer (TNBC). A heterocyclic-ligated monofunctional Pt(II) complex PtL with a unique action of mode was designed and investigated. PtL induced DNA single-strand breaks and caused genomic instability in TNBC cells. Mechanism studies demonstrated that PtL disrupted lysosomal acidity and function, which in turn triggered lysosome-dependent cell death. Furthermore, PtL showed convincing suppression in the tube forming and cell migratory abilities against the metastatic potential of TNBC cells. The synthesis and investigation of PtL revealed its potential value as an anti-TNBC drug and extended the family of monofunctional Pt(II) complexes. [ABSTRACT FROM AUTHOR]

In the present study, 12-tungestocobaltic acid, H5CoW12O40, was immobilized on nano silica from rice husk (CoW@NSiO2) to develop a novel, efficient, heterogeneous and recyclable nano catalyst for the synthesis of β-enaminones. It is apparent from acidity and cyclic voltammetric measurements that, the catalyst is electroactive and undergoes reversible redox transitions, as well as it is contains strong acid sites and mobile protons. As evidenced from mechanistic investigations, CoW@NSiO2 can catalyze the synthesis of β-enaminones with two simultaneous ways: electron transfer and Brønsted acid mechanisms. In order to confirm the synthesis of enaminones through simultaneous mechanisms of electron transfer and acidity, the model reaction was carried out in the presence of K5Co as an electroactive catalyst and CoW@NSiO2 with electron scavenger as an acid catalyst. The results showed that the reaction proceeded simultaneously through both mechanisms. There is evidence that the electron transfer property of this catalyst is most pronounced in this type of organic reactions. The catalyst demonstrated outstanding performance, and the methodology proved to be versatile, yielding excellent results across a wide range of substrates. It is worth mentioning that aliphatic amines were well-tolerated in the process and produced β-enaminone compounds with excellent yields and short reaction times. Also, reactions with dimedone, a cyclic 1,3-diketone, delivered moderate product yields. Additionally, the catalyst showed remarkable recyclability, maintaining its activity for a minimum of five consecutive cycles without any noticeable decline. Notably, the cyclic voltammetric and acidity measurements revealed that the catalyst's electron transfer property and Brønsted acidity remained unchanged after five runs. [ABSTRACT FROM AUTHOR]

Raman spectra of aqueous sodium borate solutions, with and without excess NaOH, NaCl, and LiCl, have been obtained from perpendicular and parallel polarization measurements acquired using a custom-built sapphire flow cell over the temperature range 25 to 300 °C at 20 MPa. The solvent-corrected reduced isotropic spectra include a large well-defined band at 865 cm−1 which overlaps with the boric acid B(OH)3 band at 879 cm−1, and becomes increasingly intense at elevated temperatures. This band does not correspond to the spectrum of any other previously reported aqueous polyborate ions, all of which have symmetric stretching bands at frequencies below that of borate, [B(OH)4]−, at 745 cm−1. Based on the classic high-temperature potentiometric titration study by R. E. Mesmer, C. F. Baes and F. H. Sweeton, Acidity measurements at elevated temperatures. VI. Boric acid equilibriums, Inorg. Chem., 1972, 11, 537–543, the new band was postulated to arise from a diborate ion, [B2(OH)7]− or [B2O(OH)5]−. Ab initio density functional theory (DFT), together with chemical modelling studies, suggest that it is most likely [B2(OH)7]−. Thermodynamic formation quotients derived from the peak areas showed variations with ionic strength as well as charge-balance discrepancies, which suggest one or more unidentified minor equilibrium species may also be present. The most likely candidate is the divalent diborate species [B2O2(OH)4]2− which is also predicted to have a band near 865 cm−1 and is postulated to be present as a sodium ion pair. These are the first quantitative Raman spectra ever reported for borate-rich solutions under such conditions and provide the first spectroscopic evidence of a diborate species at PWR reactor coolant temperatures. [ABSTRACT FROM AUTHOR]

Based on the concept of the proton hydrate-anion complex [H(H2O)n]+A−, equations are proposed that characterize the catalytic activity of the proton in aqueous solutions of three acids: sulfuric, hydrochloric, and chloric. The equations are based on the linear dependence of the value of "excessive acidity" on the logarithm of the relative stoichiometric concentration of water Х = f(log C*w) in acid solutions with a predominance of water (Н2О/НА > 1). Using the directly proportional dependence of the Hammett function (–H0) on the sum of parameters (log C*H+ + mX), two-parameter equations were obtained for calculating the complex function of acidity –Hw0 = log C*H+ + Blog C*w (standard state—pure water, C0w). The equations make it possible to calculate the function Hw0 at a given acid concentration, having only data on the concentrations of the proton CH+ and water Hw0, i.e. avoiding the use of the ratio of the activity coefficients of the components included in parameter X. The function Hw0 collectively reflects the participation of proton and water in the acidity of the medium, practically reproduces the experimental values of H0 obtained by different authors in the concentration range from pure water to 68 wt % (H2SO4), 40% (HCl), 70% (HClO4), combines the pH and H0 scales. It is concluded that the Blog Hw0 contribution, which characterizes the participation of water in the hydration shells of ions, is determined by their nature and plays no less important role in characterizing the acidity of the medium than the proton itself. The final tables of the concentration dependence of the values Hw0 for each of the acids are given. The paper represents a methodological review, since it is based on a critical analysis of experimental literature data. [ABSTRACT FROM AUTHOR]

In this work, vanadium replaced molybdenum atoms generating catalysts with general formulae H3+nPMo12-nVnO40 (n = 0,1, 2 and 3), which were used in the acetalization of alkyl alcohols with terpene aldehyde (β-citronellal and methyl alcohol were model substrates). The initial focus was evaluating how the vanadium load impact the catalytic activity of phosphomolybdic acids and trying to link this effect with their structural properties. A comparison of performance achieved by the catalysts revealed that among phosphomolybdic acids (i.e., with V1, V2, and V3 atoms/per anion), the vanadium monosubstituted phosphomolybdic acid was the most active and selective toward the formation of β-citronellyl acetal. The effects of main reaction variables such as time, temperature, catalyst load, type of alcohol, and vanadium load on conversion and selectivity of the reactions were investigated. Remarkably, while in methyl alcohol, only acetal was formed, in the presence of other alkyl alcohols terpene ethers (geranyl and β-citronellyl) were also obtained. Their highest activity of H4PMo11VO40 was attributed to the greatest Brønsted acidity strength, as demonstrated by the acidity measurements and infrared spectroscopy analysis. This catalyst has advantages over traditional liquid mineral acid catalysts and provides an alternative route to synthesize acetal and terpene ethers. [ABSTRACT FROM AUTHOR]

Synthesised N-substituted heterocyclic derivatives have ubiquitous applications in fine chemicals, pharmaceuticals, organic electronic materials, and agrochemicals. Numerous reports of photocatalytic C–N coupling in aid of a 5 W visible light source are documented in the literature which facilitates the cost reducibility, reusability, and promising methods for reaction. In this present work, we have designed and synthesised a benzimidazole-based sulphonic acid functionalized porphyrin photocatalyst (BSAFPPc) and confirmed by analytical techniques such as FT-NMR, FT-IR, and SEM/EDX. The BSAFPPc demonstrated an optical energy gap of 1.12 eV by using DRS. Further, the acidic potential was scrutinized by the Hammett acidity function which is H0 = 0.99. The BSAFPPc was used for the C–N coupling of morpholine, and inactivated aryl halides comprising electron-donating (–NH2, –OMe, –CH3) and withdrawing groups (–CHO, –NO2). This photocatalytic reaction produced an excellent practical yield from 60 to 90%. Further, the scope was extended to benzimidazole, pyrrole, indole and 1,2,4-triazole. The reaction has been experimented in an in-house homemade reactor system in a presence of a 5 W visible light source in an additive-free environment at ambient conditions. The photocatalyst was durable up to six photocatalytic cycles. The photocatalyst maintained its heterogenous nature which was asserted by the leaching test. [ABSTRACT FROM AUTHOR]

A selective and greener route in the synthesis of various alkyl acrylates was achieved by highly conjugated porphyrin entangled with 1,2,4-triazole-based ionic liquid photocatalyst (CPTILP). The process of acrylic acid (AA) esterification was carried out by exposure to 5 W LED light under ambient conditions in a laboratory-based photocatalytic reactor. The CPTILP photocatalyst was synthesized and characterized by different techniques such as 1H NMR and FT-IR. Additionally, its acidic nature and bandgap energy was analyzed by Hammett acidity function and Diffuse Reflectance spectra using a UV–Visible spectrophotometer. The screening of CPTILP photocatalyst for esterification specified that the protocol was quite effective to acquire the desired product with an admirable (75%) yield, using 20 mg photocatalyst, 1:1.5 ratio (AA: ROH) under 5 W light in 20 h at room temperature. This is the first photocatalytic methodology avoiding polymerization of acrylic acid without using any solvent and inhibitors at ambient conditions. After completion of the reaction, CPTILP was easily recovered from the reaction mixture by filtration and reused for the next cycle for 6 successive runs with a competitive yield. With the optimum conditions, industrially important alkyl acrylates were obtained with moderate to good yield, compared to existing protocols, using methanol to 1-hexanol. The simple protocol using CPTILP opens a new window to the researchers and industry for the production of alkyl acrylates, without forming any by-product under very mild photocatalytic reaction conditions. [ABSTRACT FROM AUTHOR]

Tumor extracellular acidity and chemoresistance are regarded as the main obstacles to achieving optimal chemotherapeutic efficacy in tumor therapy. Herein, a new kind of acid-cascade P-S-Z nanoparticles (NPs) is developed to relieve extracellular acidosis and enhance chemotherapy without causing drug resistance. The P-S-Z NPs selectively accumulate in tumors and then regulate the release of S-Z NPs containing syrosingopine (Syr) and acid-activated prodrug ZMC1-Pt depending on the extracellular acidity. Benefiting from their small size and positive surface charge, S-Z NPs are easily internalized by tumor cells in deep tumor tissue, facilitating the release of Syr to inhibit lactic acid excretion and ultimately enhance cell acidosis. The prolonged intracellular acidosis not only inhibits tumor cell proliferation, but also continuously triggers the activation of ZMC1-Pt prodrug, a platinum-based chemotherapeutic drug that effectively eliminates cancer cells and restores wild-type p53 function to prevent tumor chemoresistance. As a proof of concept, this is a promising strategy to transfer the adverse effect of intracellular acidosis to facilitate chemotherapy. This well-designed delivery system effectively kills tumor cells without causing significant tumor drug resistance, thus opening a new window to treat cancer. The drug delivery nanoparticles (P-S-Z NPs) obtained by co-loading syrosingopine (Syr) and acid-activated prodrug ZMC1-Pt are developed to relieve extracellular acidosis and enhance chemotherapy without causing tumor drug resistance. This nanoplatform with great biocompatibility can selectively accumulate in tumors, then regulate extracellular acidity and restore the functions of wild-type p53 to prevent the emergence of chemoresistance. [Display omitted] [ABSTRACT FROM AUTHOR]

In this review, we discuss gas phase experimentation centered on the measurement of acidity and proton affinity of substrates that are useful for understanding catalytic mechanisms. The review is divided into two parts. The first covers examples of organocatalysis, while the second focuses on biological catalysis. The utility of gas phase acidity and basicity values for lending insight into mechanisms of catalysis is highlighted. [ABSTRACT FROM AUTHOR]

In this work, vanadium-substituted cesium phosphomolybdate salts with general formulae Cs3+nPMo12−nVnO40 (n = 0, 1, 2, and 3) were synthesized and evaluated in the acetalization of benzaldehyde with alkyl alcohols. All the catalysts were characterized through Raman, infrared, and ultraviolet–visible spectroscopies, powder X-ray diffraction patterns, isotherms of N2 desorption/adsorption, and measurements of acidity strength. The catalytic activity of cesium phosphomolybdovanadate salts was evaluated in the acetalization reactions of benzaldehyde with alkyl alcohols. Among the salts tested, the Cs4PMo11V1O40 was the most active and selective catalyst in the conversion of benzaldehyde to methyl benzyl acetal and benzoic acid, which was obtained without the use of an oxidant agent. The impact of the main reaction parameters on the conversion and selectivity was evaluated by varying the content of vanadium per heteropolyanion, catalyst load, temperature, and alkyl alcohols. The greatest activity of the Cs4PMo11V1O40 salt was assigned to the highest Brønsted acidity strength, as demonstrated by the acidity measurements and analysis of their surface properties. This solid catalyst has advantages over traditional liquid homogenous catalysts, such as low corrosiveness, a minimum generation of residues and effluents, and easy recovery/reuse. In addition, its synthesis route is easier and quicker than solid-supported catalysts and comprises a potential alternative route to synthesize acetals. [ABSTRACT FROM AUTHOR]

It has been about 36 years since the first published paper about the calorimetry and adsorption (Cal-Ad) method by Prof. Drago. These separated methods are very old and important characterization tools for different molecules and materials, as recognized in chemistry. The idea of coupling these two techniques arose from the need to have more information about the thermodynamic parameters of a catalyst. The Cal-Ad method provides a measure of the magnitude (Ki), strength (−∆Hi), and quantity (ni) of sites present in a catalyst. The original idea is based on the application of the donor-acceptor concept using the Electrostatic Covalent Model, ECW in the areas of catalysis and material chemistry. Particularly, enthalpy measurements of acidity are directly related to the activity of various catalysts in a variety of reactions. Currently, more than twenty-five catalysts have been carefully characterized by this method in addition to spectroscopic and other thermal methods. Thus, this review seeks to present the fundamentals of the method and show different applications of the characterized catalysts for a variety of reactions in order to use these data as an alternative to choose a catalyst for an acid-dependent type reaction. [ABSTRACT FROM AUTHOR]

In this research, two novel dicationic Brönsted acidic ionic liquids based on diethylamine were synthesized and characterized by various spectroscopic techniques such as Fourier transform infrared spectroscopy, Proton NMR (1H NMR), Carbon-13 NMR (13C NMR), Mass spectrometry as well as Hammett acidity function. The obtained results showed that the dicationic ionic liquid (DIL) to be efficient catalyst in the synthesis of 1, 8-dioxooctahydroxanthenes, 14-aryl-14H-dibenzo [a, j] xanthenes and 1, 8-dioxodecahydroacridines under solvent-free conditions. In addition, two DILs were investigated for their antibacterial activity against gram-positive and gram-negative bacterial strains by the agar diffusion method. Ease of preparation and handling of the catalyst, high yield of products in short reaction times, reusability of the catalyst, as well as high antibacterial activity of DILs are the main advantages of the present method. [ABSTRACT FROM AUTHOR]

The particles of heterogeneous catalysts differ greatly in size, morphology, and most importantly, in activity. Studying these catalyst particles in batch typically results in ensemble averages, without any information at the level of individual catalyst particles. To date, the study of individual catalyst particles has been rewarding but is still rather slow and often cumbersome1. Furthermore, these valuable in-depth studies at the single particle level lack statistical relevance. Here, we report the development of a droplet microreactor for high-throughput fluorescence-based measurements of the acidities of individual particles in fluid catalytic cracking (FCC) equilibrium catalysts (ECAT). This method combines systematic screening of single catalyst particles with statistical relevance. An oligomerization reaction of 4-methoxystyrene, catalyzed by the Brønsted acid sites inside the zeolite domains of the ECAT particles, was performed on-chip at 95 °C. The fluorescence signal generated by the reaction products inside the ECAT particles was detected near the outlet of the microreactor. The high-throughput acidity screening platform was capable of detecting ~1000 catalyst particles at a rate of 1 catalyst particle every 2.4 s. The number of detected catalyst particles was representative of the overall catalyst particle population with a confidence level of 95%. The measured fluorescence intensities showed a clear acidity distribution among the catalyst particles, with the majority (96.1%) showing acidity levels belonging to old, deactivated catalyst particles and a minority (3.9%) exhibiting high acidity levels. The latter are potentially of high interest, as they reveal interesting new physicochemical properties indicating why the particles were still highly acidic and reactive. [ABSTRACT FROM AUTHOR]

This work is focused on the age-old challenge of developing optical sensors for acidity measurements in low-pH aqueous solutions (pH < 5). We prepared halochromic (3-aminopropyl)amino-substituted quinoxalines QC1 and QC8 possessing different hydrophilic–lipophilic balance (HLB) and investigated them as molecular components of pH sensors. Embedding the hydrophilic quinoxaline QC1 into the agarose matrix by sol-gel process allows for fabrication of pH responsive polymers and paper test strips. The emissive films thus obtained can be used for a semi-quantitative dual-color visualization of pH in aqueous solution. Being exposed to acidic solutions with pH in the range of 1–5, they rapidly give different color changes when the analysis is performed in daylight or under irradiation at 365 nm. Compared with classical non-emissive pH indicators, these dual-responsive pH sensors allow for an increase in the accuracy of pH measurements, particularly in complex environmental samples. pH indicators for quantitative analysis can be prepared by the immobilization of amphiphilic quinoxaline QC8 using Langmuir–Blodgett (LB) and Langmuir–Schäfer (LS) techniques. Compound QC8 possessing two long alkyl chains (n-C8H17) forms stable Langmuir monolayers at the air–water interface, and these monolayers can be successfully transferred onto hydrophilic quartz and hydrophobic polyvinylchlorid (PVC) substrates using LB and LS techniques, respectively. The 30-layer films thus obtained are emissive, reveal excellent stability, and can be used as dual-responsive pH indicators for quantitative measurements in real-world samples with pH in the range of 1–3. The films can be regenerated by immersing them in basic aqueous solution (pH = 11) and can be reused at least five times. [ABSTRACT FROM AUTHOR]

Sulphonic acid‐functionalized polymeric ionic liquids (PILs) were synthesized and applied into catalytic conversion of cellulose into levulinic acid (LA). The structure, thermal stability, and Hammett acidity function (H0) of PILs were characterized and all were more thermostable than those of small‐molecular ionic liquids (IL). At the optimum reaction conditions, the LA yield was maximized to 79.4 % by catalyst [Pim]CH3SO3. More importantly, catalyst [Pim]CH3SO3 performed well in other biomass conversion, such as cellobiose, starch and rice husk. The product LA can be easily extracted by methyl isobutyl ketone from the reaction mixture. The PILs with high catalytic activity were easily recycled with an LA yield up to 68.9 % even after five cycles. These sufficient PILs will offer new approaches for transforming biomass to platform chemicals. [ABSTRACT FROM AUTHOR]

In this study, a comparison of the intra-regional variation in the quality of Argan oil and pomace collected from 12 cooperatives in the Essaouira region (Morocco) during the COVID-19 period was carried out. All studied Argan pomaces together with the extraction solvents showed a significant difference (p < 0.05) in the total phenolic compounds, flavonoids, and tannins contents. The proteins, residual oils, total sugars, and total reducing sugars contents in the collected pomaces vary considerably among cooperatives of origin, with maximum averages of 50.45%; 30.05%; 3.82 milligrams of glucose equivalent per gram of dry matter; and 0.53 milligrams of glucose equivalent per gram of dry matter, respectively. Therefore, it is a very valuable ingredient for livestock feed and some cosmetic products that may contain it. The remaining Argan oil content in the pomace varied significantly among cooperatives, ranging from 8.74 to 30.05%. Pomace from traditional extraction recorded the highest content (30.05%), showing that the artisanal and modern extraction processes are not standardized. The measurements of acidity, peroxide value, specific extinction coefficient at 232 nm and 270 nm, and conjugated dienes were carried out in accordance with Moroccan Standard 08.5.090 in order to qualitatively classify all investigated Argan oils. Accordingly, the analyzed oils were categorized as "extra virgin Argan oil," "fine virgin Argan oil," "ordinary virgin Argan oil," and "lampante virgin Argan oil." Therefore, several factors can explain these variations in quality grades, both endogenous and exogenous. Overall, the variation observed in the obtained result allows us to deduce the most significant variables impacting the quality of Argan products and by-products. [ABSTRACT FROM AUTHOR]

The nanostructured lanthanide-silica materials of the Ln–SiO2 type (Ln = La, Ce, Pr, Nd, Eu, Gd, Dy, Yb, Lu) were synthesized by the hydrothermal method at 100 °C, using cetyltrimethylammonium as a structural template, silica gel and sodium silicate as a source of silicon, and lanthanide oxides, with Si/Ln molar ratio = 50. The resulting materials were calcined at 500 °C using nitrogen and air, and characterized by X-ray diffraction (XRD), Fourier-Transform infrared absorption spectroscopy, scanning electron microscopy, thermogravimetry (TG), surface area by the BET method and acidity measurements by n-butylamine adsorption. The XRD and chemical analysis indicated that the SiO2 presented a hexagonal structure and the incorporation of lanthanides in the structure changes the properties of the Ln–SiO2 materials. The heavier the lanthanide element, the higher the Si/Ln ratio. The TG curves showed that the decomposition of the structural template occurs in the materials at temperatures below 500 °C. The samples showed variations in specific surface area, mean pore diameter and silica wall thickness, depending on the nature of the lanthanide. The incorporation of different lanthanides in the silica generated acid sites of varied strength. The hydrothermal stability of the Ln–SiO2 materials evaluated at high temperatures, evidenced that the properties can be controlled for application in adsorption and catalysis processes. [ABSTRACT FROM AUTHOR]

Cetyl trimethyl ammonium bromide (CTAB) assisted Oxidation of hypoxanthine (HXAN), and xanthine (XAN) alkaloids by Mn(VII) occurred smoothly in presence of aqueous Bronsted acid (HClO4, H2SO4) media. The rate of oxidation of HXAN, XAN by Mn(VII) was enhanced due to an increase in [HClO4] / [H2SO4] in the presence of CTAB at a constant temperature. Reaction kinetics obeyed I-order in [Mn(VII)], [HXAN], or [XAN] at constant temperature and acid concentration in micellar (CTAB) conditions. In this present work, the acidity functions developed by Zucker-Hammett, Bunnett, and Bunnett-Olsen were used for analyzing rate enhancement, and the probable reaction mechanism that involves water moiety in the slow step has been proposed according to the criteria of Bunnett-Olsen. [ABSTRACT FROM AUTHOR]

Summary: For a quality assessment of milk and dairy products, the optical methods are used. In this paper, the use possibility is investigated of the optical method of photoluminescence for the milk acidity value finding out. The spectral measurements were carried out on a diffraction spectrofluorimeter in the range of 200–500 nm. The milk acidity measurement accuracy was controlled by the titrimetric method. It is established that as far as milk sours, the excitation spectra in the range of 200–500 nm decrease; but there are qualitative changes in the range of 350–500 nm. With acidity growth, the photoluminescence flux decreases if it is excited by the radiation value λe = 262 nm, grows at λe = 385 nm and decreases at λe = 442 nm. It is advisable to control the milk acidity in terms of the photoluminescence fluxes ratio Φ385/Φ442. The linear approximation of the function Φ385/Φ442(K) is statistically reliable (the determination factor R2 = 0.99). [ABSTRACT FROM AUTHOR]

The Water Quality Index (WQI) is an important parameter in describing the water resources' suitability for human uses and is one of the most effective methods of describing water quality and indicative of assessing water quality and suitability for human utilization and the health of ecosystems. WQI of the Canadian Council of Ministers of the Environment (CCME) was used in the study to describe the Shatt al-Arab water quality in Basrah Southern Iraq, and its suitability for drinking use. The data for analyzing river water samples were adopted from five stations along the river every month during the years from 2014 to 2018 by the Iraqi Ministry of Environment, as it included the measurement of acidity function PH, Dissolved Oxygen DO, phosphorous PO4, nitrate NO3, Calcium Ca, potassium K, magnesium Mg, sodium Na, Total Hardness TH, sulfates SO4, chlorides Cl, Electrical Conductivity EC, Total Soluble Salts TDS, and Alkalinity ALK. The distributions of water quality index values along the river were mapped by GIS techniques. Study results were referring to illustrate the poor level of the water quality status of Shatt al-Arab in all study periods at all monitoring stations. The reason for this is due to the deterioration of fresh water quality drained from the Tigris and Euphrates, and the provision of salt wedges from the Arabian Gulf. However, with the continuous discharge of sewage water, industrial and oil effluents and sewage discharged from urban areas, the water quality of Shatt al-Arab was declined during the study period. [ABSTRACT FROM AUTHOR]

Exploration of sustainable insulation solutions for HVDC converter transformers has prompted the investigation of palm methyl ester (PME) as a viable alternative to traditional mineral oil. This study presents a detailed thermal ageing analysis of PME-impregnated thermally upgraded kraft (TUK) paper, focusing on critical elements of the oil–paper insulation system. The research emphasizes the importance of interactions between the oil and paper components, particularly in influencing long-term insulation performance and reliability under HVDC stress. Acidity measurements confirmed PME’s chemical stability over time, while scanning electron microscopy (SEM) provided insights into ageing-induced morphological changes in TUK paper, affecting its mechanical integrity and dielectric strength. The degree of polymerization was evaluated to assess the extent of chemical degradation, crucial for predicting the insulation system's lifespan. Furthermore, the study examined key electrical properties, including DC breakdown voltage, quasi-DC conductivity using the polarization depolarization current method, and space charge dynamics analysed with pulsed electro-acoustic techniques. Results showed that PME-impregnated paper offered superior performance over mineral oil-impregnated paper, with a higher DC breakdown voltage, lower quasi-DC conductivity, more stable charge distribution, and a significantly reduced electric field distortion rate (28% vs. 16%). These findings underscore PME’s potential as a viable, eco-friendly insulation solution for HVDC applications. The study advocates for further investigation into PME in oil–paper systems, emphasizing the pivotal role of these specific interactions and properties in enhancing the development and efficiency of HVDC technologies. [ABSTRACT FROM AUTHOR]

• Evaluated adsorption isotherm and kinetic models of DGA and LN resins. • Higher-order isotherm and kinetics models demonstrated a superior fit. • Film and intraparticle diffusion are involved in adsorption processes. • Thermodynamic studies revealed that Gibbs free energy increased with temperature. Two commercially available extraction chromatography (EXC) resins containing N,N,N',N'-tetra-n-octyldiglycolamide (DGA Resin, Normal, 50 – 100 μm) and Bis(2-ethylhexyl) phosphate (LN Resin, 100 – 150 μm) were used as adsorbents to study fundamental adsorption properties such as thermodynamic values, equilibrium isotherms, and kinetic uptake models for terbium(III) adsorption. Weight distribution ratios (D w) for terbium on DGA and LN resins were measured using a [160Tb]Tb3+radiometric tracer in nitric acid as a function of acidity, temperature, initial analyte concentration, and equilibrium time. The D w values showed increasing binding affinity for DGA resin at high nitric acid concentrations and decreasing binding affinity for LN resins. Thermodynamic studies for DGA and LN resins revealed that the Gibbs free energy (ΔG) increased consistently with temperature. To model equilibrium data, increasingly higher parameter equilibrium isotherm models (Henry (1) < Langmuir, Freundlich (2) < Redlich-Peterson (3) < Fritz-Schluender (4)) were compared on their root mean squared errors (RMSE) and adjusted determination coefficients to determine the most applicable model. In all cases, the empirical four-parameter Fritz-Schluender isotherm demonstrated a superior fit. Similar comparisons for reaction-based kinetic models (Pseudo-first-order < Pseudo-second-order < Pseudo-n-order) revealed that the higher-order PNO model yielded a superior fit of kinetic data for both resins. However, in some cases, adsorption isotherms and kinetic models could also be modeled by a lower-order model with minimal change in error parameters. Weber-Morris plots revealed that two linear sections are observed for each resin, where the first linear segment is attributed to fast (film diffusion) adsorption of terbium, followed by slower intraparticle diffusion of terbium through the pores as the rate-limiting step. Based on the Weber-Morris plot, both film and intraparticle diffusion are involved in controlling the kinetic rate of adsorption for DGA and LN resins. [ABSTRACT FROM AUTHOR]

Sourness is one of the basic yet essential tastes of coffee that is chemically composed of acids and quantitatively represented in the pH scale. Current tools for measuring the acidity level in roasted coffee beans, including traditional methods, require brewing sample coffee and probing the chemical components, limiting the applicability to end customers seeking to estimate the acidity level before choosing the right coffee beans to purchase. This paper proposes a novel approach to directly estimate the acidity levels from roasted coffee beans images by framing the problem into an image classification task, where a picture of roasted coffee beans is categorized into its appropriate pH range. As a result, end customers could simply estimate coffee beans' acidity levels by taking photos with conventional cameras. Multiple traditional machine learning and deep learning algorithms are validated for their ability to predict the correct acidity levels. The experiment results reveal that EfficientNet yields the best performance with an average F1 of 0.71 when trained with images from separate portable devices. Practical Applications: The research's findings could also be extended to applications in the coffee‐industrial settings, such as automatically monitoring roasted coffee beans' quality from image and video streams. For end customers, the trade‐off between efficacy and efficiency of the EfficientNet algorithm is also investigated, which sheds light on the implementation aspects of state‐of‐the‐art deep learning models in portable devices such as smartphones or cameras. Such applications could prove to be a cost‐effective and convenient solution for customers to quickly measure roasted coffee beans' sourness before deciding to purchase. [ABSTRACT FROM AUTHOR]

A molecular system comprising a cationic zinc complex and an amino acid‐derived ambident ligand having phosphate and carboxylate binding sites undergoes a series of rearrangements in which the metal cation migrates autonomously from one site to another. The location of the metal is identified by the circular dichroism spectrum of a ligated bis(2‐quinolylmethyl)‐(2‐pyridylmethyl)amine (BQPA) chromophore, which takes a characteristic shape at each binding site. Migration is fuelled by the decomposition of trichloroacetic acid to CO2 and CHCl3, which progressively neutralises the acidity of the system as a function of time, revealing in sequence binding sites of increasing basicity. The migration rate responds to control by variation of the temperature, water content and triethylamine concentration, while an excess of fuel controls the duration of an induction period before the migration event. [ABSTRACT FROM AUTHOR]

For a period of several years the philosopher of science Hasok Chang has promoted various inter-related views including pluralism, pragmatism, and an associated view of natural kinds. He has also argued for what he calls the persistence of everyday terms in the scientific view. Chang claims that terms like phlogiston were never truly abandoned but became transformed into different concepts that remain useful. On the other hand, Chang argues that some scientific terms such as acidity have suffered a form of "rupture", especially in the case of the modern Lewis definition of acids. Chang also complains that the degree of acidity of a Lewis acid cannot be measured using a pH meter and seems to regard this as a serious problem. The present paper examines some of these views, especially what Chang claims to be a rupture in the definition of acidity. It is suggested that there has been no such rupture but a genuine generalization, on moving from the Brønsted-Lowry theory to the Lewis theory of acidity. It will be shown how the quantification and measurement of Lewis acidity can easily be realized through the use of equilibrium theory and the use of stability constants. [ABSTRACT FROM AUTHOR]

In the present work, two sets of the Co/ZSM-5 mesoporous catalysts with different acidity and Co loadings varying from 1 to 5 and 10 wt% were prepared using mesoporous ZSM-5-A (Si/Al = 50) and ZSM-5-B (Si/Al = 150) as support. X-ray diffraction (XRD) analysis showed that the Co3O4 phase was formed in the surface of catalysts and the reducibility of Co3O4 nanoparticles on the ZSM-5-B was greater in comparison with that on the ZSM-5-A solid. In situ FTIR of pyridine adsorption characterization confirmed that all of the Co/ZSM-5 catalysts contained both Lewis (L) and Brønsted (B) acid sites, with a relatively balanced B/L ratio ranging from 0.61 to 1.94. Therefore, the Si/Al molar ratio in ZSM-5 affected both the surface acidity and the cobalt oxide reducibility. In the esterification of unsaturated omega-9 oleic acid with methanol, under the optimal reaction conditions (temperature 160 °C, catalyst concentration 2 g/L, methanol/oleic acid molar ratio 30, and reaction time 180 min), the biodiesel selectivity reached 95.1% over the most active 10 wt% Co/ZSM-5-B catalyst. The higher esterification activity of the Co/ZSM-5-B catalysts can be correlated with the greater amount of B and L acid sites, the balanced B/L ratio, and the higher reducibility of Co3O4 nanoparticles. The oleic acid esterification reaction followed the bifunctional mechanism of combining metal function (dispersed Co3O4 with a greater reducibility) with the acidity function (both B and L acid sites with a relative balanced B/L ratio) on the catalysts, which may help in providing a deep understanding of the esterification pathways and benefiting the design of novel bifunctional catalysts for biofuel production. [ABSTRACT FROM AUTHOR]

The classical Hantzsch reaction is a simple and utmost efficient protocol for the synthesis of biologically and pharmacologically important 1,4-dihydropyridine derivatives. The present study deals with the utilization of modified heteropoly acid (HPA) catalysts (5 wt% WO x -FeP and 5 wt% MoO x -FeP) in the synthesis of novel Hantzsch 1,4-dihydropyridines, which contains diphenylsulfone moiety via one-pot synthesis strategy under ultrasound irradiation. The developed protocol is simple and green procedure for the synthesis of 1,4-dihydropyridines and is applicable to synthesize different 1,4-dihydropyridine derivatives. The synthesized HPA catalysts offered a sustainable methodology to produce excellent products yields (88–92%) of 1,4-dihydropyridine derivatives. The catalysts were characterized by XRD, Raman, FT-IR, DRUV- vis , XPS, H 2 -TPR, N 2 -physisorption and acidity measurements. The HPA supported iron phosphate nanotubes (FeP) catalysts offered enhanced the catalytic performance through the improved Lewis acid site density, redox properties and surface area, compared to the parent phosphomolybdic and phosphotungstic acids. Moreover, the synthesized catalysts can be easily separated from reaction system and reused for six times efficiently without significant loss of activity. [Display omitted] • Iron phosphate nanotubes supported heteropoly acids (HPA) were synthesized. • FeP-supported HPA catalysts portrayed better reducibility and acidity. • Hantzsch reaction was followed to synthesize dihydropyridine derivatives. • 5W-FeP catalyst showed a superior catalytic efficiency towards Hantzsch reaction. • Robust catalyst re-used for six times prove its suitability for Hantzsch reaction. [ABSTRACT FROM AUTHOR]

This research is focused on the development of pH indicators based on the quinoxaline signaling group for acidic aqueous solutions (pH 1–5). A push–pull quinoxaline QC1 in which two electron-donating (3-aminopropyl)amino substituents are attached to positions 6 and 7 of the electron-deficient quinoxaline moiety was prepared using the palladium-catalyzed C–N cross-coupling reaction. The 3-aminopropyl residues are mostly protonated in aqueous solutions below pH 8, thus serving as hydrophilizing substituents that render quinoxaline derivative QC1 water-soluble in this range of acidities and useful for measurements in the pH range of 1–5. This chromophore is a dual optical chemosensor that exhibits shifts of both absorption and emission bands in response to external stimuli. The presence of naturally relevant metal cations (13 ions) does not interfere with spectrophotometric and fluorescence measurements of the optical response of aminoquinoxaline in the visible region. Moreover, these spectral changes are easily observed by the naked eye, allowing for rapid semi-quantitative analyses under "in-field" conditions. [ABSTRACT FROM AUTHOR]

A comparative study to quantify acid dissociation constant (pKa) of acetylsalicylic acid by applying the parallel factor analysis (PARAFAC) to three‐way data arrays of UV spectroscopic and spectrochromatographic measurements was presented. In data recording and data collection stages, the spectrochromatograms of 20 μg/mL acetylsalicylic acid in different mobile phases having seven different pH levels were recorded, and a cubic data set was created with time x wavelength x pH dimensions. UV spectra of the analyte in the concentration range of 10–30 μg/mL and in seven different pH media were recorded and arranged as a three‐way array with dimensions, wavelength x concentration x pH. To estimate the pKa by two different chemometric strategies, the cubic data sets were decomposed into trilinear components, which allowed to predict the pKa in the pH profiles. In practice, the three‐way analysis‐based UV spectroscopic and spectrochromatographic methods didn't include a titration procedure and had a second‐order advantage over traditional pKa determination methods. As a result, this investigation on the rapid and accurate estimation of the acidity constant of acetylsalicylic acid provided alternative and practical ways to determine the pKa of active pharmaceutical ingredients in the future. [ABSTRACT FROM AUTHOR]

A new hydraulic cavitation‐assisted epoxidation scheme was developed by using a cost‐effective, environment‐friendly, and recyclable solid‐acid catalyst. SnO2‐Al2O3‐NiO/SO42− solid‐acid catalysts were prepared using co‐precipitation and impregnation methods, which were characterised by several techniques and analysed using the Hammett acidity function. The prepared catalysts were found to have a large specific surface area (53.95 m2/g) and abundant acid sites (94 μmol/g). Exhibits higher stability and more effective catalytic activity compared with H2SO4. Under the optimal reaction conditions, the relative conversion to oxirane of 86.97% was obtained in only 1.5 h of reaction time. Moreover, the catalyst could be easily separated and showed satisfactory catalytic activity after five reuse cycles. The current work has clearly demonstrated that the application of hydraulic cavitation technology to the solid‐acid‐catalysed epoxidation reaction of soybean oil can shorten the reaction time, increase the relative conversion to oxirane, and be a viable method with promising applications. [ABSTRACT FROM AUTHOR]

At present, the trend towards partial replacement of petroleum-derived fuels by those from the revaluation of biomass has become of great importance. An effective strategy for processing complex biomass feedstocks involves prior conversion to simpler compounds (platform molecules) that are more easily transformed in subsequent reactions. This study analyzes the metal–organic frameworks (MOFs) that contain Zr metal clusters formed by ligands of terephthalic acid (UiO-66) and aminoterephthalic acid (UiO-66-NH2), as active and stable catalysts for the esterification of levulinic acid with methanol. An alternative synthesis is presented by means of ultrasonic stirring at room temperature and 60 °C, in order to improve the structural properties of the catalysts. They were analyzed by X-ray diffraction, scanning electron microscopy, infrared spectroscopy, X-ray photoelectron spectroscopy, microwave plasma atomic emission spectroscopy, acidity measurement, and N2 adsorption. The catalytic reaction was carried out in a batch system and under pressure in an autoclave. Its progress was followed by gas chromatography and mass spectrometry. Parameters such as temperature, catalyst mass, and molar ratio of reactants were optimized to improve the catalytic performance. The MOF that presented the highest activity and selectivity to the desired product was obtained by synthesis with ultrasound and 60 °C with aminoterephthalic acid. The methyl levulinate yield was 67.77% in batch at 5 h and 85.89% in an autoclave at 1 h. An analysis of the kinetic parameters of the reaction is presented. The spent material can be activated by ethanol washing allowing the catalytic activity to be maintained in the recycles. [ABSTRACT FROM AUTHOR]

In this paper, an interesting Brönsted acidic dicationic ionic liquid based on piperazine was prepared via two-step synthesis. The structure of the dicationic ionic liquid (DIL) was confirmed with various techniques including Fourier transform infrared spectroscopy (FT-IR), Proton NMR (1H NMR), Carbon-13 NMR (13C NMR), mass spectroscopy (MS), acid–base titration as well as Hammett acidity function. Catalytic activity of this novel Brönsted acidic DIL was examined in the xanthene synthesis. High yield of product, short reaction time, easily recovery and reusing of the catalyst, and the absence of organic solvents are some of the merits of the developed procedure. [ABSTRACT FROM AUTHOR]

Molybdophosphoric acid/silica-alumina composites were synthesized through a process, in which the heteropolyacid was impregnated on different silica-aluminas, obtained by sol-gel. Three different techniques were used to prepare the samples. The catalysts were prepared by incipient wetness impregnation and different thermal treatments were applied. The hybrid systems were characterized by SBET, XRD, and acidity measurements. The catalytic activity of these materials was tested in the solvent-free cyclization of 1-(2-hydroxyphenyl)-3-(2-furyl)-1,3-propanedione to 2-(2-furyl)-chromones. The transformation gives very good yields of product, free of secondary products. Environmental benign procedure, and easy catalyst separation, is relevant features of this methodology. In this way, the catalyst can be used and reused six cycles without loss of catalytic activity. The most active catalyst was also used in the solvent-free cyclization of 1-(2-hydroxyphenyl)-3-(2-furyl)-2-propen-1-one and the methodology can be extended to the synthesis of other 2-(2-(furyl)-chromones and chromanones. The green context for this new procedure was confirmed by greenmetrics parameters. [ABSTRACT FROM AUTHOR]

Objective: To evaluate in vitro erosive effect of analgesics on primary tooth enamel. Material and Methods: The pH and the titratable acidity measurements of the medicines were performed in triplicate using a digital pH meter. Enamel slabs of primary teeth flat and polished were selected by initial surface microhardness analysis. Medications were selected and specimens were assigned into five groups (n=12): Dalsy; Magnopyrol; Paracetamol; Tylenol; and distilled water (negative control). Specimens were immersed in 5 ml of each group solution for 30 min, 4x/day for three days and stored in artificial saliva at 37 °C between immersions and at night. Final microhardness was determined. The data were submitted to Oneway ANOVA and Tukey's test. Scanning electron microscopy (SEM) analysis was performed in three specimens of each group. Results: Medicines showed acidic pH and mean values of titratable acidity ranged from 1.46 to 11.66 ml of 0.1N NaOH. The mineral loss of Magnopyrol was statistically significant in relation to the control group (p<0.01). Magnopyrol showed higher values when compared to Tylenol (p<0.05). SEM images displayed microstructure alterations in the Paracetamol group. Conclusion: Despite the low pH values, only Magnopyrol showed greater enamel softening. Paracetamol demonstrated morphological changes in primary tooth enamel. [ABSTRACT FROM AUTHOR]

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