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Copyright of Chemical Industry / Hemijska Industrija is the property of Association of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A simple and efficient one-pot synthesis was developed for the preparation of S-alkyl thiolcarbamates from xanthogenate without catalyst using water as a solvent. The water can be recycled after removal of the product. The significant features of this protocol are: operational simplicity, mild reaction conditions, recycling of solvent and high product yields. Starting basic alkyl xanthogenate reacts with alkyl ammonium sulfate (aryl ammonium sulfate) and hydrogen peroxide (molar ratio 1:0.55:1) in water at 40 °C for 1 h, followed by additional heating at 70–110 °C for 1–2.3 h. Good to excellent yields were achieved using ammonium sulfate in 10 % molar excess. Graphical abstract: [Figure not available: see fulltext.] [ABSTRACT FROM AUTHOR]

Copyright of Chemical Industry / Hemijska Industrija is the property of Association of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Chemical Industry / Hemijska Industrija is the property of Association of Chemical Engineers and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Linear free energy relationships (LFER) were applied to the IR, ¹H- and 13C--NMR spectral data in N-alkyl and N-cycloalkyl cyanoacetamides. N-alkyl and N-cycloalkyl cyanocetamides were synthesized from corresponding amine and ethyl cyanoacetate. A number of substituents were employed for alkyl substitution, and fairly good correlations were obtained, using simple Hammett equation. In N-alkyl and N-cycloalkyl cyanoacetamides substituent cause SCS of N-H hydrogen primarily by steric interaction, polar subtituent effect influences SCS shift of C=O carbon, while steric effect of N-alkyl substituent causes IR stretching frequencies of N-H, C=O and CN group. The conformations of investigated compounds have been studied by the use of semiempirical PM6 method, and together with LFER analysis, give a better insight into the influence of such a structure on the transmission of electronic substituent effects. Negative ρ values for several correlations (reverse substituent effect) were found. [ABSTRACT FROM AUTHOR]

A series of some new pyridone arylazo dyes was synthesized from the corresponding diazonium salts and 4,6-diphenyl-3-cyano-2- pyridone using the classical reaction for the synthesis of the azo compounds. The structures of these dyes were confirmed by UV-vis, FTIR and 1H-NMR spectroscopic techniques. The solvatochromism of the dyes was evaluated with respect to visible absorption properties in various solvents. The effects of solvent dipolarity/polarizability and solvent/solute hydrogen bonding interactions were analyzed by means of the linear solvation energy relationship concept proposed by Kamlet and Taft. The 2-pyridone/2-hydroxypiridine tautomeric equilibration was found to depend on the substituents as well as on the solvents. [ABSTRACT FROM AUTHOR]

The 13C NMR chemical shifts of the C2 carbon atom in the heteroaromatic nuclei of seventeen 5-(3- and 4-substituted arylazo)-4,6-dimethyl-3-cyano-2-pyridones were determined in deuterated DMSO solution. For quantitative assessment of the substituent effects on the 13C NMR chemical shifts simple and extended Hammett equations and Swain-Lupton equation were used. The mode of transmission of substituent effects have been discussed in a relation to the geometry of investigated molecules. The geometry data were obtained using semiempirical MNDO-PM6 energy calculations. The observed 13C NMR substituent chemical shifts were correlated with literature 13C NMR data for the corresponding 3- and 4-substituted-2′,6′-dimethylazobenzenes and 3- and 4-substituted azobenzenes. A good linear dependence obtained in this way, provided a basis to discuss the influence of the ortho-methyl groups on the degree of coplanarity of azobenzene and pyridone systems, and on the efficiency of transmission of electronic substituent effect from one ring to the other one. [ABSTRACT FROM AUTHOR]

3-Cyano-4-(ethoxymethyl)-6-methyl-2-pyridone, an important precursor in the synthesis of vitamin B6, is obtained in the addition reaction between 2-cyanoacetamide and 1-ethoxy-2,4-pentanedione catalyzed by lipase from Candida rugosa (triacylglycerol acylhydrolases, EC 3.1.1.3). This work shows new experimental data and mathematical modeling of the lipase-catalyzed synthesis of 3-cyano-4-(ethoxymethyl)-6-methyl-2-pyridone. Kinetic measurements were performed at 50 °C with an enzyme concentration of 1.2 % w/v. The experimental results were fitted with two kinetic models: the ordered bi-ter and ping-pong bi-ter model, and the initial rates of the reaction were found to correlate best with the ping-pong bi-ter mechanism with inhibition by 2-cyanoacetamide. The obtained specificity constants indicated that lipase from C. rugosa had a higher affinity towards 1-ethoxy-2,4-pentanedione compared to 2-cyanoacetamide. [ABSTRACT FROM AUTHOR]

Linear free energy relationships (LFER) were applied to the IR, 1H- and 13C- -NMR spectral data of N-(substituted phenyl)-2-cyanoacetamides. A variety of substituents were employed for phenyl substitution and fairly good correlations were obtained using the simple Hammett and the Hammett-Taft dual substituent parameter equations. The correlation results of the substituent induced 13C-NMR chemical shifts (SCS) of the C1, C=O and N-H atom indicated different sensitivity with respect to electronic substituent effects. A better correlation of the SCSC=O with a combination of electrophilic and nucleophilic substituent constants indicated a significant contribution of extended resonance interaction (π-delocalization) within the π1-unit. The conformations of the investigated compounds were studied using the DFT B3LYP/6-311G"" method and, together with the results of 13C-NMR and IR spectroscopic studies, a better insight into the influence of such a structure on the transmission of electronic substituent effects was obtained [ABSTRACT FROM AUTHOR]

Abstract: Three commercially available polymers (Sepabeads® EC-EP, Sepabeads® EC-HA and Purolite® A-109) were tested for potential application as supports for covalent immobilization of lipase from Candida rugosa by analyzing some critical properties of immobilized enzymes such as enzyme loading, activity and activity immobilization yield. Among them, lipase covalently immobilized on Sepabeads® EC-EP via epoxy groups appeared to show the best performance in a standard hydrolytic reaction. Therefore, it was selected and assayed in the esterification of butyric acid and geraniol to produce geranyl butyrate, first in a batch system followed by continuous geranyl butyrate synthesis in a fluidized bed reactor, as one being potentially applicable for large-scale production. Based on statistical analysis, optimal conditions for the production of geranyl butyrate by selected, immobilized lipase in the batch system are recommended as: temperature at 25–30°C, water concentration at 3.6% (v/v) and acid/alcohol molar ratio at 2.5. A set of optimal conditions for the ester synthesis in a fluidized bed reactor system has also been determined, specifically, flow rate at 10mLmin−1, temperature at 35°C, water concentration at 2% (v/v), substrate concentration at 0.1M and acid/alcohol ratio at 2.0. Implementation of the optimized parameters in a batch system and in a fluidized bed reactor enabled production of target ester with high molar conversion, at > 99.9% for 48h in the batch process, and 78.9% for 10h in fluidized bed reactor. Although when assayed at their optimal conditions, lower molar conversion was achieved in the fluidized bed reactor system compared to the batch system, the volumetric productivity in fluidized bed reactor was more than five fold higher than that obtained in the batch system. [Copyright &y& Elsevier]

Using the cyclic voltammetry, it has been shown that hydrogen evolution at a gold electrode is necessary in the electrochemical activation of azithromycin dihydrate and erythromycin A. After four hours of the potential holding at -1.2 V vs. SCE, the pH of the electrolyte has been changed from 8.40 to 8.96; from 8.40 to 8.77 in the presence of erythromycin A, and from 8.40 to 9.18 in the presence of azithromycin, indicating the reaction of the hydrogen species with antibiotics. This effect has been confirmed by using the phenolphthalein indicator and by analysing colours of the solutions by UV-Vis, as well as by FTIR spectroscopy. Under the identical experimental conditions at the gold electrode, in contrast to azithromycin dihydrate and erythromycin A, roxithromycin and midecamycin electroactivity promotion has been obtained during the first forward sweep starting from the area of a double layer region. [ABSTRACT FROM AUTHOR]

Herein, we report the synthesis and characterization of nine 6-hydroxy-4-methyl-3-pyridinium-2-pyridone based azo dyes, wherein, eight of them being novel. Used building blocks ensured water solubility of six dyes and made them adequate to be used for dyeing in an alkaline environment contrary to the traditional application of arylazo pyridone dyes. The peculiarity of the compounds arises as they exhibit zwitterion-hydrazone equilibrium and shift from neutral to cationic dyes. It is shown that the equilibrium strongly depends on the electronic effects of the p -substituent in the phenyl moiety, as well as, pH values of the solutions. The screening of the dyeing process (by using multifiber fabric) suggested that synthesized compounds are most eligible for dyeing wool and diacetate fabrics at a pH of 8.5. Furthermore, 100% wool and diacetate fabrics were dyed and used for the dyeing assessment. A comprehensive study between dye architectures and fiber dyeing was performed. The interplay of various interactions, responsible for the dye-fiber binding, has been proposed, bearing in mind both, dyes' and fibers' structures and pH dependency. Namely, dye-wool interactions are mostly based upon charge assisted hydrogen bonds, wherein these interactions are strengthened by C–H··· π contact when dyes are affixed to diacetate. The specific nature of the dye is affected by the electronic effect of the p -substituents of the phenyl moiety, upon which, a detailed study on fibers affinity towards zwitterionic and/or hydrazone forms has been outlined. Most of the dyed fabrics exhibit good to excellent ultraviolet protection, while dyed diacetate shows good washing fastness. [Display omitted] • Nine pyridinium pyridone arylazo dyes are synthesized and characterized. • The screening of dyeing was performed on multifiber fabric at three pH values. • Dyes are most eligible for dyeing wool and diacetate at pH value 8.5 • The adhesion of dyes correlates well with the share of hydrazone tautomeric form. • The electronic substituent effects play a significant role in the dye-fiber binding. [ABSTRACT FROM AUTHOR]

• Hydrated zwitterionic crystals of pyridone derivatives have been obtained. • Water and zwitterions interlocked into crystal packing through an interplay of interactions. • By coupling the experimental and calculated data of crystal structure, packing is elucidated. • The architecture depends on the number of water molecules and the nature of interactions. Two pyridone derivatives, bearing the pyridinium moiety (1), or dimethylpyridinium moiety (2), have been synthesized and their crystal structures have been determined. The compounds crystalize in hydrated zwitterionic forms with either two (1·2H 2 O) or four (2·4H 2 O) water molecules. The zwitterionic networks contain different types of water clusters, generated into channels, incorporating them into the network by sandwiching. The type of channel depends on the crystal lattice and the nature of non-covalent interactions established between zwitterions as well as the number of water molecules incorporated into the architecture. 1 affords tubes filled in with water channels formed by water tetramers, contrary to 2 , which affords a layered network altering the zwitterionic layer and the layer formed by water tetramers and hexamers. A detailed study of intermolecular interactions of both crystal structures and a quantification of interaction energies has been performed using PIXEL lattice energy calculations, giving an insight to a quantitative evaluation of interactions through Coulombic, disperse, repulsion and polarization energies. The strongest pairwise, in both structures, is found to be a dipole–dipole interaction between oppositely charged heterocyclic rings. The differences in the crystal packings of these hydrates have been elucidated by the fingerplot analysis. The comparative studies between experimental and calculated (DFT) data of molecules 1·H 2 O and 2·4H 2 O for systems of different complexity are performed. Furthermore, correlations of experimental and calculated bond lengths and the simulation of compound solvation with the CPCM model are done. [Display omitted] [ABSTRACT FROM AUTHOR]

Seven novel azo dyes with 2-pyridone and dihydropyrimidinone moieties have been synthesized and thoroughly characterized. The azo-hydrazone tautomerism has been investigated by experimental and theoretical approaches. The optimizations of geometries have been performed with density functional theory (DFT). The vibrational and NMR spectra were calculated and correlated with experimental ones. Furthermore, quantum chemical descriptors were calculated and MEP maps were plotted to determine biological reactivity of dyes. The antioxidant assay evinced that 5 , 6 and 7 are promising antioxidant candidates. In vitro cytotoxic activity was studied against three malignant cell lines: prostate adenocarcinoma (PC-3), lung carcinoma (A549) and chronic myelogenous leukemia (K562), as well as against human normal lung fibroblasts (MRC-5), using MTT assay. Examination of cytotoxic effects on human cancer cell lines showed the concentration dependent cytotoxicity of all investigated compounds. The K562 cells were the most sensitive to the cytotoxicity of the compounds 3 , 5 and 6 , wherein compound 5 was particularly prominent and selective in cytotoxic action between K562 (24.97 μM) and PC-3 (48.98 μM) cancer cells, and normal MRC-5 (91.11 μM) cells. Moreover, the cell cycle analysis of compound 5 was examined in K562 cells, by flow cytometry, to study its mechanism of anticancer action. Finally, in silico evaluation of physicochemical parameters, druglikeness and ADME properties showed that investigated compounds are orally bioavailable with no permeation to the blood brain barrier. Image 1 • Novel azo pyridone dihydropyrimidinone based dyes are synthesized and characterized. • Experimental and DFT approaches confirm that the most stable tautomer is hydrazone. • New structures exhibited promising anticancer and antioxidant properties. • Dyes show concentration dependent cytotoxicity against tested cancer cells. • Novel dyes may serve for further development of new anticancer drugs. [ABSTRACT FROM AUTHOR]

A series of nine 5-(4-substituted phenylazo)-3-amido-6-hydroxy-4-methyl-2-pyridones were synthesized and characterized by FT–IR, 1H and 13C NMR, UV–Vis, and PL spectroscopy. Photophysical properties of the dyes were examined in solvents of various polarities and at different pH values. The solvent effects on the absorbance and emission spectral shift were analyzed using Lippert–Mataga, Reichardt–Dimroth and Kamlet-Taft equations. Moreover, UV–Vis absorption and emission frequencies were correlated with Hammett substituent constants applying the linear free energy relationships. DFT calculations of the investigated dyes were accomplished to determine their structural and electronic properties. Image 1 • The absorption and emission spectra of nine arylazo pyridone dyes were recorded. • The solvent effects on the absorbance and emission spectral shift were analyzed. • The conformational analysis showed that the investigated dyes are in hydrazone form. • The existence of two conformational forms of hydrazone tautomer was confirmed. • Excellent correlations between computational and experimental data were established. [ABSTRACT FROM AUTHOR]

Thermal degradation properties of 5-(4-substitutedphenylazo)-3-amido-6-hydroxy-4-methyl-2-pyridones and 5-(4-substitutedphenylazo)-3-cyano-6-hydroxy-4-methyl-2-pyridones dyes, differing in electron withdrawing and electron donating substituents in para -position of diazo components were examined. The structure of the synthesized compounds has been confirmed by 1H NMR,13C NMR, FTIR, UV–Vis and XRD analysis techniques. The results obtained with thermogravimetric analysis (TGA) – derivative thermogravimetry (DTG) and differential thermal analysis (DTA) were combined with GC-mass spectral fragmentation to obtain thermal decomposition mechanism. Non-isothermal kinetics were monitored by application of TGA-DTG-DTA. For Kinetic behavior of the investigated dyes during their degradation in an inert atmosphere, Kissinger, Ozawa, Flynn-Wall-Ozawa (FWO) and Kissinger-Akahira-Sunose (KAS) isoconversional (model-free) methods were applied. It was found that different thermal stabilities of investigated dyes are the consequence of their different chemical structures, including diverse substituents. Image 1 • TGA-DTG and DTA analysis of pyridone azo dyes were performed. • The thermal analysis has shown that dyes are stable up to 250 °C. • The degradation occurs mainly due to breaking of C N bond of hydrazone form. • The kinetic parameters indicated a change in the reaction pathways. • The investigated dyes are suitable for use in high-temperature processes. [ABSTRACT FROM AUTHOR]

Researchers are faced with everyday demands for safer and more efficient therapy for many diseases, especially serious one such as various types of cancer. Numerous anticancer drugs are poorly-water soluble and therefore their encapsulation and controlled release remain quite challenge. In present study, we deepened our research of hydrophilic carrier based on poly(methacrylic acid) and casein (PMAC) by investigating its potential for encapsulation and controlled release of novel poorly water-soluble dihydropyrimidion-azo-pyridon compound (DHPMP). DHPMP is a dye that has been proven to show cytotoxic activity against chronic myeloid leukemia K562 cells. By encapsulating DHPMP into the carrier and delivering it into the intestines, DHPMP absorption could be the fastest and the number of therapeutic doses and side effects can be reduced. Carriers based on PMAC and DHPMP (PMAC-DHPMP) were synthetized and characterized by FTIR, SEM and single compression tests. The swelling behavior of PMAC-DHPMP carriers and cumulative DHPMP release were investigated depending on the amount of crosslinker and encapsulated DHPMP in two media which were simulating pH environments in human stomach and intestines. The prolonged and controlled release of DHPMP was achieved. In vitro cytotoxic activity of PMAC-DHPMP carriers against K562 cells and the cell cycle analysis showed great potential of the carriers for application in leukemia treatment., (© 2022 Wiley Periodicals LLC.)

In order to improve the performance of theoretical UV-Vis spectra predictions, a theoretical and experimental study of solvatochromic properties of ten azo pyridone dyes has been performed. For quantitative estimation of intermolecular solvent-solute interactions, a concept of the linear solvation energy relationships has been applied using Kamlet-Taft and Catalán models. Theoretical UV-Vis spectra for all dyes have been calculated using four TD-DFT methods in nine different solvents with the aim to define the most reliable model. Finally, new polylinear equations for more accurate theoretical prediction of UV-Vis maxima are developed using empirical Kamlet-Taft and Catalán solvent parameters as additive corrections for specific and nonspecific solvent-solute interactions., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

A selection of best combination of adequate immobilization support and efficient immobilization method is still a key requirement for successful application of immobilized enzymes on an industrial level. Eupergit ® supports exhibit good mechanical and chemical properties and allow establishment of satisfactory hydrodynamic regime in enzyme reactors. This is advantageous for their wide application in enzyme immobilization after finding the most favorable immobilization method. Methods for enzyme immobilization that have been previously reported as efficient considering the obtained activity of immobilized enzyme are presented: direct binding to polymers via their epoxy groups, binding to polymers via a spacer made from ethylene diamine/glutaraldehyde, and coupling the periodate-oxidized sugar moieties of the enzymes to the polymer beads. The modification of the conventionally immobilized enzyme with ethylenediamine via the carbodiimide route seems to be a powerful tool to improve its stability and catalytic activity.

Kaolin showed as a very perspective carrier for the enzyme immobilization and it was used for the adsorption of horseradish peroxidase (HRP). The effects of the enzyme concentration and pH on the immobilization efficiency were studied in the reaction with pyrogallol and anthraquinone dye C.I. Acid Violet 109 (AV 109). In addition, Fourier transform infrared spectroscopy, scanning electron microscopy and analysis by Brunauer-Emmett-Teller were performed for kaolin, thermally activated kaolin and the immobilized enzyme. It has been shown that 0.1 IU of HRP-kaolin decolorized 87 % of dye solution, under the optimal conditions (pH 5.0, temperature 24 °C, dye concentration 40 mg/L and 0.2 mM of H2O2) within 40 min. The immobilized HRP decolorization follows the Ping Pong Bi-Bi mechanism with dead-end inhibition by the dye. The biocatalyst retained 35 ± 0.9 % of the initial activity after seven cycles of reuse in the decolorization reaction of AV 109 under optimal conditions in a batch reactor. The obtained kinetic parameters and reusability study confirmed improvement in performances of k-HRP compared to free, indicating that k-HRP has a great potential for environmental purposes.

To complement a previous UV study, we present a quantitative evaluation of substituent effects on spectroscopic data ((1)H and (13)C NMR chemical shifts as well as FT-IR absorption frequency) applied to N,N'-bisarylmalonamides, using simple and extended Hammett equations as well as the Swain-Lupton equation. Furthermore, the DFT CAM-B3LYP/6-311+G(d,p) method was applied to study the impact of different solvents on the geometry of the molecules and their spectral data. Additionally, experimental data are correlated with theoretical results; excellent linear dependence was obtained. The overall results presented in this paper show that N,N'-bisarylmalonamides are prominent candidates for model molecules.

Two anthraquinonic dyes, C.I. Acid Blue 225 and C.I. Acid Violet 109, were used as models to explore the feasibility of using the horseradish peroxidase enzyme (HRP) in the practical decolorization of anthraquinonic dyes in wastewater. The influence of process parameters such as enzyme concentration, hydrogen peroxide concentration, temperature, dye concentration, and pH was examined. The pH and temperature activity profiles were similar for decolorization of both dyes. Under the optimal conditions, 94.7% of C.I. Acid Violet 109 from aqueous solution was decolorized (treatment time 15 min, enzyme concentration 0.15 IU/mL, hydrogen peroxide concentration 0.4 mM, dye concentration 30 mg/L, pH 4, and temperature 24°C) and 89.36% of C.I. Acid Blue 225 (32 min, enzyme concentration 0.15 IU/mL, hydrogen peroxide concentration 0.04 mM, dye concentration 30 mg/L, pH 5, and temperature 24°C). The mechanism of both reactions has been proven to follow the two substrate ping-pong mechanism with substrate inhibition, revealing the formation of a nonproductive or dead-end complex between dye and HRP or between H2O2 and the oxidized form of the enzyme. Both chemical oxygen demand and total organic carbon values showed that there was a reduction in toxicity after the enzymatic treatment. This study verifies the viability of use of horseradish peroxidase for the wastewaters treatment of similar anthraquinonic dyes.

Ultrafine CeO2-δ nanopowder, prepared by a simple and cost-effective self-propagating room temperature synthesis method (SPRT), showed high adsorption capability for removal of different azo dyes. Batch type of adsorption experiments with fixed initial pH value were conducted for the removal of Reactive Orange 16 (RO16), Methyl Orange (MO), and Mordant Blue 9 (MB9). The equilibrium adsorption data were evaluated using Freundlich and Langmuir isotherm models. The Langmuir model slightly better describes isotherm data for RO16 and MO, whereas the Freundlich model was found to best fit the isotherm data for MB9 over the whole concentration range. The maximum adsorption capacities, determined from isotherm data for MO, MB9, and RO16 were 113, 101, and 91 mg g(-1) respectively. The adsorption process follows the pseudo-second-order kinetic model indicating the coexistence of chemisorption and physisorption. The mechanism of azo dye adsorption is also discussed.