Microwave Assisted Esterification of Aryl/Alkyl Acids Catalyzed by N-Fluorobenzenesulfonimide

The susceptibility of the carbonyl group towards nucleophilic attack affords the construction of various organic compounds. Thus, investigations of carbonyl activation applying greener methodologies are highly important. In the present work, among the investigated N-halo compounds, N-fluorobenzenesulfonimide (NFSi) has been found as an efficient and selective catalyst in the reaction of direct esterification of aryl and alkyl carboxylic acids supported by microwave (MW) irradiation. The comprehensive esterification of different benzoic acids and mono-, di-and tri-carboxy alkyl derivatives was performed, whereby significant reaction time reductions were achieved. The presented method used NFSi as an easily manipulatable, non-metal, water-and air-tolerant catalyst, allowing simple synthetic and isolation procedures and energy saving, compared to conventional methodologies. Importantly, in contrast to esterification under thermal conditions, where N-halo compounds behave as pre-catalysts, in the MW-supported protocol, a distinct reaction mechanism has been proposed that assumes NFSi as a sustainable catalyst. Moreover, a scale-up of the industrially important derivative was performed

Višeslojne ugljenične nanocevi kao nosač lipaze za organsku sintezu: pregled najnovijih trendova

Lipase-catalyzed organic reactions have been widely practiced in the past three decades. Especially interesting are insoluble/immobilized forms due to providing a possibility of facile use and recyclability, thus reducing process costs, and making the procedure more environmentally friendly. Carbon-based supports have been extensively exploited for this purpose, because of neutral and biodegradable nature and thermal and chemical stability. Their high specific surface area, characteristic surface morphology and lower mass transfer resistances play a vital role in the performance of the attached enzyme. This review paper presents an overview of the main aspects of lipase immobilized on multi-walled carbon nanotubes (MWCNTs). Moreover, different immobilization strategies to achieve a biocatalyst with improved performances are discussed. Furthermore, as lipases are considered to have high commercial worth for synthesis of valuable organic molecules, the second part of the paper is dedicated to the overview of the most important industrial sectors in which these nanobiocatalysts have been used. In specific, applications in biodiesel production, flavour ester synthesis and racemization are summarized.Lipaze su poslednjih decenija široko rasprostanjeni katalizatoriu raznovrsnim organskim reakcijama. Posebno su interesantne u imobilisanom/nerastvornom obliku jer je na ovaj način olakšana njihova upotreba uz mogućnost recikliranja i ponovne upotrebe čime se smanjuju troškovi samog procesa i postupak je ekološki prihvatljiviji. Kao nosači za vezivanje nanomaterijali na bazi ugljenika, posebno ugljenične nanocevi, su našli primenu zbog svojih izuzetnih fizičkih, mehaničkih i hemijskih svojstava. Njihova velika specifična površina, karakteristična površinska morfologija i smanjen otpor prenosu mase igraju vitalnu ulogu u performansama vezanog enzima. Ovaj pregledni rad predstavlja prikaz glavnih aspekata lipaze imobilisane na višeslojne ugljenične nanocevi i različitih strategija imobilizacije za dobijanje biokatalizatora sa poboljšanim svojstvima. Takođe, kako su lipaze enzimi od velikog komercijalnog značaja za organsku sintezu i primenu u biotehnologiji, drugi deo rada posvećen je pregledu najvažnijih industrijskih sektora u kojima su ovi nanobiokatalizatori našli primenu. Shodno tome, dat je pregled proizvodnje biodizela, mirisnih estara i racemizacij

Enzymatic synthesis of vitamin B6 precursor

3-Cyano-4-ethoxymethyl-6-methyl-2-pyridone is an important precursor in the synthesis of vitamin B6, obtained in the addition reaction between 2-cyanoacetamide and 1-ethoxy-2,4-pentanedione catalyzed by lipase from Candida rugosa (triacylglycerol ester hydrolases, EC 3.1.1.3). This work shows new experimental data and mathematical modeling of lipase catalyzed synthesis of 3-cyano-4-ethoxymethyl-6-methyl-2-pyridone, starting from 1-ethoxy-2,4-pentanedione and 2-cyanoacetamide. Kinetic measurements were done at 50 oC with enzyme concentration of 1.2 % w/v. 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 a ping-pong bi-ter mechanism with inhibition by 2-cyanoacetamide. Obtained specificity constants indicated that lipase from C. rugosa had higher affinity towards 1-ethoxy-2,4-pentanedione and less bulky substrates. [Projekat Ministarstva nauke Republike Srbije, br. 172013, br. III 46010 and br. 172049

Elektrohemijsko kvantitativno određivanje sertralina u farmaceutskim proizvodima na elektrod iod zlata u bikarbonatnom elektrolitu

The electrochemical characterization of sertraline standard at gold electrode was at first performed by cyclic voltammetry measurements (CV) in pH 8.4 bicarbonate buffer. Then Au electrode was evaluated for the quantitative determination of sertraline using square wave voltammetry (SWV). Namely, (2-hydroxypropyl)-β-cyclodextrin (HPβCD) sertraline inclusion complexe was employed to enhance the electrode sensitivity of the drug determination. Using the proposed SWV technique, the anodic current peak of sertraline oxidation was linear within a concentration range of 0.1–0.5 μM with a limit of detection (LOD) of 2.0 10-8 M and a limit of quantification (LOQ) of 6.7 10-8 M. In the case of inclusion complex of the sertraline with HPβCD, a good linearity range of 0.1–0.9 μM was obtained with a LOD of 2.6 10-8 M and a LOQ of 8.8 10-8 μM. Comparing the regression equations, it can be concluded that the sensitivity in the presence of inclusion complex can be up to 5 times higher. The applicability of the developed method was confirmed by the analysis of this drug in pharmaceutical formulation.Elektrohemijska karakterizacija standarda sertralina je urađena cikličnom voltametrijom(CV) u pH 8.4 bicarbonatnom puferu. Elektroda od zlata je zatim testirana za kvantitativno određivanje sertralina koristeći voltametriju sa pravougaonim impulsima (SWV). Inkluzioni kompleks (2-hydroxypropyl)-β-cyclodextrin (HPβCD) sertralina je testiran u cilju poboljšanja osetljivosti electrode za kvantitativno određivanje leka. SWV tehnikom je pokazano da je anodni strujni vrh oksidacije sertralina linearan u opsegu koncentracija 0.1–0.5 μM uz granicu detekcije (LOD) od 2.0 10-8 M i granicu kvantifikacije (LOQ) od 6.7 10-8 M. Inkluzioni kompleks sertralina sa HPβCD je ispoljio linearnost u opsegu koncentracija od 0.1–0.9 μM uz LOD of 2.6 10-8 M i LOQ od 8.8 10-8 μM. Analizom eksperimentalnih podataka može se zaklučiti da je osetljivost electrode od zlata za određivanje sertraline porasla više od pet puta kada je lek vezan u inkluzioni kompleks. Primenljivost razvijene metode je potvrđena uspešnim određivanjem leka u farmaceutskim oblicima

Synthesis and physicochemical evaluation of new chitosan-based scaffolds for potential application in biomedicine

Chitosan is a natural polymer obtained by deacetylation of chitin. Due to its biocompatibility and biodegradability, chitosan-based materials have a wide range of biomedical applications in wound dressings, drug delivery systems, and tissue engineering. Also, studies in the fields of organic and medicinal chemistry show that compounds based on the pyridone core exhibit biological properties including antimicrobial, anticancer, and antioxidant activity, and moreover have the potential as new therapeutics for various diseases from cardiovascular to antitumor therapy. In this study, new biomaterials were synthesized using low and medium molecular weight chitosan polymers and pyridone-based hydrazone. In order to improve stability of the obtained scaffolds, scaffolds’ neutralization was carried out using ethanol and sodium hydroxide solutions. The interactions established between chitosan polymer chains and pyridone compound were analyzed by FT-IR spectroscopy. Swelling and degradation tests of the materials were studied in water and PBS, and the influence of different polymer molecular weights on the scaffolds’ properties was evaluated. The results indicated that synthetized scaffolds have a high potential for biomedical use

Recovering the Soybean Hulls after Peroxidase Extraction and Their Application as Adsorbent for Metal Ions and Dyes

This study is aimed at extending the soybean hulls' lifetime by their utilization as an adsorbent for metal ions (Cd2+ and Cu2+) and dyes (Reactive Yellow 39 (RY 39) and Acid Blue 225 (AB 225)). ATR-FTIR spectroscopy, FE-SEM microscopy, and zeta potential measurements were used for adsorbent characterization. The effect of the solution's pH, peroxidase extraction, adsorbent particle size, contact time, the pollutant's initial concentration, and temperature on the soybean hulls' adsorption potential was studied. Before peroxidase extraction, soybean hulls were capable of removing 72% Cd2+, 71% Cu2+ (at a pH of 5.00) or 81% RY 39, and 73% AB 225 (at a pH of 3.00). For further experiments, soybean hulls without peroxidase were used for several reasons: (1) due to their observed higher metal ion removal, (2) in order to reduce the waste disposal cost after the peroxidase (usually used for wastewater decolorization) extraction, and (3) since the soybean hulls without peroxidase possessed significantly lower secondary pollution than those with peroxidase. Cd2+ and Cu2+ removal was slightly increased when the smaller adsorbent fraction (710-1000 μm) was used, while the adsorbent particle size did not have an impact on dye removal. After 30 min of contact time, 92% and 88% of RY 39 and AB 225 were removed, respectively, while after the same contact time, 80% and 69% of Cd2+ and Cu2+ were removed, respectively. Adsorption of all tested pollutants follows a pseudo-second-order reaction through the fast adsorption, intraparticle diffusion, and final equilibrium stage. The maximal adsorption capacities determined by the Langmuir model were 21.10, 20.54, 16.54, and 17.23 mg/g for Cd2+, Cu2+, RY 39, and AB 225, respectively. Calculated thermodynamic parameters suggested that the adsorption of all pollutants is spontaneous and of endothermic character. Moreover, different binary mixtures were prepared, and the competitive adsorptions revealed that the soybean hulls are the most efficient adsorbent for the mixture of AB 225 and Cu2+. The findings of this study contribute to the soybean hulls' recovery after the peroxidase extraction and bring them into the circular economy concept

Optical and antioxidative properties of 5-(2,6-Dimethylphenyl)- 6-Hydroxy-4-Methyl-2-Oxo-1,2-Dihydropyridine-3-Carboxamide

A new heterocyclic azo dye 5-(2,6-dimethylphenyl)-6-hydroxy-4-methyl-2-oxo-1,2- dihydropyridine-3-carboxamide was synthesized and structurally characterized by elemental analysis, FTIR, 1H and 13C NMR spectroscopy techniques. These analysis have confirmed that synthesized dye exists in the tinctorial strongest tautomeric form, hydrazone form. The dye is characterized by reflection spectrum, while absorption and emisson spectra are recorded in nine different solvents. The antioxidant activity of the synthesized dye has been chemically tested and has been shown to have great potential as an antioxidant molecule

Addressing the environmental problems of wastewater: reducing the pollution while providing multifunctional wool fabrics

The reduction of water pollution represents one of the priority topics of the EU’s goal to achieve climate neutrality by 2050. Considering this, the concept of reusing the same dyebath for multiple dyeing cycles is proposed. For this purpose, two pyridinium-based azo pyridone dyes with improved solubility and affinity towards different fibers, are used for dyeing wool fabric. It is demonstrated that the dye concentration in wastewater could be reduced up to four times by recirculation of the same dyebath 5 times. The dyed fabrics obtained in each cycle are further characterized regarding color strength (K/S) and ultraviolet protection factor (UPF), while their antioxidant potential is evaluated by ABTS (2,2’-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid)) test. The results revealed that the proposed concept could be used for obtaining multifunctional wool fabrics by following the principles of sustainable development of reducing the effluent load in wastewater

Supplementary data for article: Tomašević, A.; Mijin, D.; Radišić, M.; Prlainović, N.; Cvijetić, I.; Kovačević, D. V.; Marinković, A. Photolysis of Insecticide Methomyl in Various Solvents: An Experimental and Theoretical Study. Journal of Photochemistry and Photobiology A: Chemistry 2020, 391. https://doi.org/10.1016/j.jphotochem.2020.112366

Supplementary material for: [https://doi.org/10.1016/j.jphotochem.2020.112366]Related to published version: [http://cherry.chem.bg.ac.rs/handle/123456789/3832

Sinteza 5-(supstituisanih fenilazo)-6-hidroksi-4-metil-3-cijano-2-piridona iz etil-3-okso-2-(supstituisanih fenilazo)butanoata

A new procedure for the synthesis of known azo pyridone dyes is presented. A series of 5-(substituted arylazo)-6-hydroxy-4-methyl-3-cyano-2-pyridones were prepared from ethyl 3-oxo-2-(substituted phenylazo)butanoates and cyanoacetamide in acetone using potassium hydroxide as a catalyst by simple refluxing the reaction mixture. The structure of these dyes was confirmed by FT-IR, NMR and UV-Vis spectroscopy.Novi postupak za sintezu poznatih azo-piridonskih boja je opisan u radu. Serija 5-(supstituisanih fenilazo)-6-hidroksi-4-metil-3-cijano-2-piridona je pripremljena iz etil-3-okso-2-(supstituisanih fenilazo)butanoata i cijanoacetamida u acetonu korišćenjem kalijum-hidroksida kao katalizatora uz zagrevanje