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The esters of substituted 1,4-dihydropyirdines (1,4-DHP) are formed in the reaction of an appropriate aldehyde and ethyl acetoacetate in the presence of concentrated water solution of ammonia. The esters form the amides by the reaction with primary amines. The series of the amides has been synthesized with the aim to analyze their chemical characteristics, antioxidant and antimicrobial activity. The amine used in this research is 2-aminothiazole. The antioxidant activity is analysed by 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2'-Azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) methods and the antimicrobial activity screening was performed by broth microdilution method, using different microbial strains. The characterization of the obtained amides was done by melting points, FTIR, NMR and elemental analysis. The possibilities for further research was suggested, which could lead to the application of selected compounds.

The derivatives of isatin have already been known to display a variety of biological activities. Therefore, the studies on their activity and its relation to structure have recently become a popular subject for investigation. The examined compounds were synthesized by the reaction of isatin and substituted primary amines and characterized by spectroscopic methods. The investigation of the antimicrobial and antioxidative activity of the synthesized compounds was performed by broth microdilution method. As for the characterization of the investigated isatin based Schiff bases, the linear solvation energy relationships (LSER) were used to analyze the solvent influence on the UV absorption maxima shifts (max), using the well known Kamlet–Taft model and taking geometrical isomers into consideration when possible. Linear free energy relationships (LFER) were used to analyze substituent effect on pKa, as well as NMR chemical shifts and max values. The antimicrobial activity and characterization were related using both experimental and theoretical methods. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172013]

The substituent and solvent effects on solvatochromism in 3-[(4-substituted) phenylamino]isobenzofuran-1(3H)-ones were studied using experimental and theoretical methodologies. The effect of specific and non-specific solvent–solute interactions on the shifts of UV–Vis absorption maxima were evaluated using the Kamlet–Taft and Catalán solvent parameter sets. The experimental results were studied by density functional theory (DT) and time-dependent density functional theory (TD-DFT). The HOMO/LUMO energies (EHOMO/ELUMO) and energy gap (Egap) values, as well as the mechanism of electronic excitations and the changes in the electron density distribution in both ground and excited states of the investigated molecules were studied by calculation in the gas phase. The electronic excitations were calculated by the TD-DFT method in the solvent methanol. It was found that both substituents and solvents influence the degree of π-electron conjugation of the synthesized molecules and affect the intramolecular charge transfer character. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172013]

The study describes the results of static, physicochemical and ballistic examination of double-based gunpowder charges, in order to establish the deviations from the demanded quality of mortar ammunition. The examinations were carried out on gunpowder samples used for laboration of mortar shells 60, 82 and 120 mm caliber and consisted of periodical measurements of the gunpowder mass loss, basic ballistic parameters, and compatibility testing of gunpowder and celluloid containers as well as chemical stability determination. The estimation of the gunpowder quality was performed by comparative analysis and the suggestions for more efficient production of it were given. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172013]

Fourteen mono- and bis-carbohydrazone ligands have been synthesized and characterized. Antioxidant activity of the substances was investigated together with possible (E)/(Z) isomerization, and explained on the most active antioxidant compound 4 in various dimethyl sulphoxide–water mixtures. The addition of water to the system was involved in the formation of hydrated molecules which was confirmed in NMR after the addition of D2O. The ligands were tested in vitro against Gram-positive and Gram-negative bacteria and fungi, and their activity was discussed in relation to the structure of investigated carbohydrazone. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. 172013]

The multistage synthesis of the multi-wall carbon nanotubes (MWCNT) modified with polyamidoamine dendrimers, A1/ and A2/MWCNT, capable of cation removal, is presented in this work, as well as novel adsorbents based on these precursor materials and modified with goethite nano-deposit, α-FeOOH, A1/ and A2/MWCNT–α-FeO(OH) adsorbents used for As(V) removal. In a batch test, the influence of pH, contact time, initial ion concentration and temperature on adsorption efficiency were studied. Adsorption data modelling by the Langmuir isotherm, revealed good adsorption capacities (in mg g-1) of 18.8 for As(V) and 60.1 and 44.2 for Pb2+ and Cd2+ on A2/MWCNT, respectively. Also, 27.6 and 29.8 mg g-1 of As(V) on A1/ and A2/MWCNT–α-FeO(OH), respectively, were removed. Thermodynamic parameters showed that the adsorption is spontaneous and endothermic processes. Results of the study of influences of competitive ions: bicarbonate, sulfate, phosphate, silicate, chromate, fluoride and natural organic matter (NOM), i.e., humic acid (HA), showed the highest effect of phosphate on the decrease of arsenate adsorption. Time-dependent adsorption was best described by pseudo-second-order kinetic model and Weber–Morris model which predicted intra-particle diffusion as a rate-controlling step. Also, activation energy (Ea / kJ mol-1): 8.85 for Cd2+, 9.25 for Pb2+ and 7.98 for As(V), were obtained from kinetic data. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III45019 and Grant no. OI 172057]

The morphological, thermal and barrier properties of low-density polyethylene/polycaprolactone-modified nanocellulose hybrid materials were investigated in this paper. Nanonocelulose/magnetite (NC-Fe3O4) nanocomposite and maleic acid functionalized NC/magnetite (NCMA-Fe3O4) nanocomposite were prepared and used as filler at various concentrations (5, 10 and 15 wt. %) in polycaprolactone (PCL) layer. PE was coated with PCL/NC/magnetite layer. The addition of the filler did not unfavorably affect the inherent properties of the polymer, especially its barrier properties. Oxygen permeation measurements show that the oxygen barrier properties of magnetite enriched PCL film were improved due to chemical activity of added material. The highest level of barrier capacity was observed for PE samples coated with PCL based composite with NCMA-Fe3O4 micro/-nanofiller, which implies the significant contribution of nanocellulose surface modification with maleic anhydride residue to improved barrier properties. [Projekat Ministarstva nauke Republike Srbije, br. III45019 i br. OI172013]

The present study reports the new facile methodology for synthesis of symmetrical and asymmetrical thioureas by an one-pot reaction of amine, carbon disulfide and oxidants: hydrogen peroxide, ethylenediamine tetraacetic acid (EDTA)/sodium percarbonate system or air. The structures of the synthesized compounds were confirmed by IR, 1H and 13C NMR and MS methods. Reaction mechanism has been proposed on the basis of reaction intermediate isolation and their structure determination. The synthetic benefits of the presented methods is reflected in the operational simplicity, mild reaction conditions, short reaction times, recycling of solvent, high purity and yield of products, absence of dangerous by-products and technological applicability at industrial scale. Considering commercial importance of the thioureas, it can be emphasized that implementation of the optimal synthesis of thiourea, based on presented methods, at industrial level of production would provide concurrent alternative to existing technologies in use. [Projekat Ministarstva nauke Republike Srbije, br. 172013]

A novel adsorbents NC-PEG, obtained by the modification of nanocellulose (NC) with PEG-6-arm amino polyethylene glycol (PEG-NH2) via maleic anhydride (MA) linker, was used for the removal of Cd2+ and Ni2+ from water. Subsequent precipitation of goethite (FO) on NC-PEG produced NC-PEG/FO adsorbent which was used for As(V) and As(III) removal. In a batch test, the influence of pH, contact time, initial ion concentration and temperature on adsorption efficiency were studied. The maximum adsorption capacities found for Cd2+ and Ni2+, obtained by the use of Langmuir model, were 37.9 and 32.4 mg g−1 at 25 °C, respectively. Also, high As(V) and As(III) removal capacity of 26.0 and 23.6 mg g-1 were obtained. Thermodynamic parameters indicate endothermic, feasible and spontaneous nature of adsorption process. Kinetic study, i.e. fitting by Weber-Morris model predicted intra-particle diffusion as a rate-controlling step. Multi-cycle reusability of both NC-PEG and NC-PEG/FO, significantly affects the affordability of techno-economic indicators for consideration of their possible application. [Ministry of Education, Science and Technological developments of the Republic of Serbia, Project No. 172013, and University of Defence, Republic of Serbia, project VA-TT/4/16-18]

The derivatives of isatin have already been reported to show a variety of biological activities. However, there has been no report on solvatochromic effect of isatin derivatives so far, and that could be of interest to study and relate to their electronic structure, as a part of the characterisation of these compounds. Linear solvation energy relationships (LSER) were used to analyze solvent influence on the UV absorption maxima shifts of investigated isatin derivatives, i.e. isatin based Schiff bases, by using Kamlet-Taft model. Linear free energy relationships (LFER) were applied to the substituent-induced NMR chemical shifts (SCS) using SSP (single substituent parameter). The obtained correlations together with theoretical calculations gave insight into the influence of the molecular conformation on the transmission of substituent effects, as well as on solute/solvent interactions. The molecular electrostatic potential (MEP) surface map was plotted over the optimized geometry of the molecules in order to visualize electron density distribution and explain origin of solvent/solute interactions. [Projekat Ministarstva nauke Republike Srbije, br. 172013]

The isatin derivatives, Schiff bases, were synthesized by the reaction of isatin and various substituted primary amines and characterized by several spectroscopic methods. Investigation of the antimicrobial activity of the synthesized compounds was performed by the agar dilution method, against different strains of bacteria and one fungi. The antioxidative activity of the synthesized compounds was also determined. Some of the compounds have shown the significant activity against the selected strains of microorganisms and the antioxidative activity. [Projekat Ministarstva nauke Republike Srbije, br. 172013 i III 46010]

The ultraviolet absorption spectra of the carboxyl group of three isomeric pyridine carboxylic acids N-oxides (picolinic acid N-oxide, nicotinic acid N-oxide and isonicotinic acid N-oxide) were determined in fourteen solvents in the wavelength range from 200 to 400 nm. The position of the absorption maxima (λmax) of the examined acids showed that the ultraviolet absorption maximum wavelengths of picolinic acid N-oxide are the shortest, and those of isonicotinic acid N-oxide acid are the longest. In order to analyze the solvent effect on the obtained absorption spectra, the ultraviolet absorption frequencies of the electronic transitions in the carboxylic group of the examined acids were correlated using a total solvatochromic equation of the form max = v0 + sπ + aα+ bβ, where υmax is the absorption frequency (1/λmax), p is a measure of the solvent polarity, β represents the scale of solvent hydrogen bond acceptor basicities and α represent the scale of solvent hydrogen bond donor acidities. The correlation of the spectroscopic data was carried out by means of multiple linear regression analysis. The solvent effects on the ultraviolet absorption maximums of the examined acids were discussed.

Quantitative structure-reactivity correlations for the kinetics of the Hantzsch's synthesis of substituted 4-phenyl-1,4-dihydropyridines in the reaction between ethyl m- and p-substituted benzylidene acetoacetate and enamine has been studied. The reaction kinetics was followed using spectrophotometric measurements. It was found that the reaction correspond to the second-order kinetics. Quantitative structure-reactivity correlations of log k with the corresponding substituent constants (s,s+,sI and sR+) using Hammett and extended Hammett equation (DSP equation). They show linear relationship with positive values of reaction constants (r). The obtained data were processed by the linear regression analysis. It is confirmed that Michael's addition of enamine to benzylidene represents the slow step of the reaction with high positive charge at the benzylidene molecule. MO calculations were performed and they were also in agreement with the conclusions derived from structure-reactivity correlations. [Projekat Ministarstva nauke Republike Srbije, br. 172013]

Protic and aprotic solvent effects on the reactivity of picolinic, nicotinic and isonicotinic acid, as well as of some substituted nicotinic acids with diazodiphenylmethane (DDM) were investigated. In order to explain the kinetic results through solvent effects, the second-order rate constants for the reaction of the examined acids with DDM were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of the multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and the transition state. The signs of the equation coefficients support the already known reaction mechanism. The solvatation models for all the investigated acids are suggested and related to their specific structure.

The Hammett correlations between 13C-NMR chemical shifts of the azomethine carbon atom and the corresponding substituent constants for thirtheen Schiff bases were established. Successful correlation of the chemical shifts with electrophilic substituent constants ó+ indicate significant resonance interaction of the substituents on the aniline ring with the azomethine carbon atom in the examined series of imines. The demand for electrons in the investigated compounds was compared to that of the N-benzylidenanilines and N-(phenyl substituted) pyridinealdimines. The way of transmission of the substituent effects was discussed and they are separated into resonance and inductive effects. Inductive effects prevail over resonance effects.

The rate constants for the reactions of diazodiphenylmethane (DDM) with 2-substituted nicotinic acids in nine aprotic solvents at 30°C were determined. The obtained second order rate constants in aprotic solvents, were correlated using the Kamlet-Taft solvatochromic equation in the complete form: log k = log k0 + sπ

Solvent effects on the reactivity of cycloalkenecarboxylic, cycloalkeneacetic, 2-substituted cyclohex-1-enecarboxylic, 2-substituted benzoic, 2-substituted cyclohex-1-eneacetic, 2-substituted phenylacetic, 2-phenylcyclohex-1-enecarboxylic, 2-phenylbenzoic and 2-phenylacrylic acids with diazodiphenylmethane (DDM) were investigated. In order to explain the kinetic results through solvent effects, the second-order rate constants for the reaction of the examined acids with DDM were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were realized by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and the transition state. The signs of the equation coefficients support the proposed mechanism. Solvation models for all the investigated acids are suggested. The quantitative relationship between the molecular structure and the chemical reactivity is also discussed.

The rate constants for the reaction of 2-substituted cyclohex-1-enecarboxylic acids and the corresponding 2-substituted benzoic acids with diazodiphenylmethane were determined in various aprotic solvents at 30 ºC. In order to explain the kinetic results through solvent effects, the second order rate constants of the reaction of the examined acids were correlated using the Kamlet-Taft solvatochromic equation. The correlations of the kinetic data were carried out by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of the contributions of the initial and transition state. The signs of the equation coefficients support the proposed reaction mechanism. The quantitative relationship between the molecular structure and the chemical reactivity is discussed, as well as the effect of geometry on the reactivity of the examined molecules.

The rate constants for the reaction of diazodiphenylmethane with 2-(2-substituted cyclohex-1-enyl)acetic acids and 2-(2-substituted phenyl)acetic acids, previously determined in seven hydroxylic solvents, were correlated using the total solvatochromic equation, of the form logk = logk0 + s¶*+ aα + bβ, the two-parameter model, logk=logk0 + s¶*+ aα and a single parameter model logk = logk0 + bβ, where ¶*is a measure of the solvent polarity, α represents the scale of solvent hydrogen bond acceptor basicities and β represents the scale of solvent hydrogen bond donor acidities. The correlations of the kinetic data were carried out by means of multiple linear regression analysis and the solvent effects on the reaction rates were analyzed in terms of initial state and transition state contributions.

The rate constants for the reaction of diazodiphenylmethane with 1-cyclopentenecarboxylic, 1-cycloheptenecarboxylic, cyclopent-1-enylacetic and cyclohept-1-enylacetic acids were determined in eight alcohols at 30 ºC using the appropriate UV-spectroscopic method. In order to explain the kinetic results through solvent effects, the second order rate constants of the examined acids were correlated using a total solvatochromic equation, of the form: log k = A0+ s¶*+aα+ bβ, where ¶* is a measure of the solvent polarity, βrepresents the scale of solvent hydrogen bond acceptor basicities and β represents the scale of solvent hydrogen bond donor acidities. The correlations of the kinetic data were carried out by means of multiple linear regression analysis. The opposite sings of the electrophilic and the nucleophilic parameters are in agreement with the well-known reaction mechanism. The results presented in this paper were compared with the kinetic data for 1-cyclohexenecarboxylic and cyclohex-1-enylacetic acids obtained under the same experimental conditions.

Rate constants for the reaction of diazodiphenylmethane with cyclohex-1-enylcarboxylic acid and 2-methylcyclohex-1-enylcarboxylic acid were determined in nine aprotic solvents, as well as in seven protic solvents, at 30°C using the appropriate UV-spectroscopic method. In protic solvents the unsubsituted acid displayed higher reaction rates than the methyl-substituted one. The results in aprotic solvents showed quite the opposite, and the reaction rates were considerably lower. In order to explain the obtained results through solvent effects, reaction rate constants (k) of the examined acids were correlated using the total solvatochromic equation of the form: log k=logk0+sπ*+aα+bβ, where π* is the measure of the solvent polarity, a represents the scale of the solvent hydrogen bond donor acidities (HBD) and b represents the scale of the solvent hydrogen bond acceptor basicities (HBA). The correlation of the kinetic data were carried out by means of multiple linear regression analysis and the opposite effects of aprotic solvents, as well as the difference in the influence of protic and aprotic solvents on the reaction of the two examined acids with DDM were discussed. The results presented in this paper for cyclohex-1-enylcarboxylic and 2-methylcyclohex-1-enylcarboxylic acids were compared with the kinetic data for benzoic acid obtained in the same chemical reaction, under the same experimental conditions.

The ultraviolet absorption spectra of cyclohex-1-enylcarboxylic acid and 2- methylcyclohex-1-enylcarboxylic acid were determined in six protic and nine aprotic solvents in the wavelength range from 200 to 400 nm. The position of the λmax of the two examined acids showed that the ultraviolet absorption maximums of cyclohex-1-enylcarboxylic acid were at consistently longer wavelengths in protic solvents than those of methylcyclohex-1-enylcarboxylic acid. The opposite was true in aprotic solvents. In order to explain the obtained results, the ultraviolet absorption frequencies of the electronic transitions in the carboxy carbonyl group of the examined acids were correlated using a total solvatochromic equation of the form: v = v0 + sп* + aα + bβ, where п* is a measure of the solvent polarity, β represents the scale of solvent hydrogen bond acceptor basicities and a represents the scale of solvent hydrogen bond donor acidities. The correlation of the spectroscopic data was carried out by means of multiple linear regression analysis. The opposing solvent effects on the ultraviolet absorption maximums of the two examined acids were discussed.