oalib

Publish in OALib Journal

ISSN: 2333-9721

APC: Only $99

Submit

Any time

2019 ( 303 )

2018 ( 556 )

2017 ( 565 )

2016 ( 810 )

Custom range...

Search Results: 1 - 10 of 338696 matches for " U??umli? Gordana S. "
All listed articles are free for downloading (OA Articles)
Page 1 /338696
Display every page Item
The study of linear solvation energy relationship for the reactivity of carboxylic acids with diazodiphenylmethane in protic and aprotic solvents
GORDANA S. U??UMLI,JASMINA B. NIKOLI?
Journal of the Serbian Chemical Society , 2009,
Abstract: 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.
Optimization of the procedure for the synthesis of calcium and sodium citrate in laboratory and semi-industrial conditions
U??umliGordana S.,Tri?ovi? Nemanja P.,Petrovi? Milan Z.,Valenti? Nata?a V.
Hemijska Industrija , 2009, DOI: 10.2298/hemind0904345u
Abstract: The aim of this investigation is the development of the optimal laboratory procedure for the synthesis of calcium and sodium citrate and the application of obtained results in a project for a semi-industrial installation for its production. These salts are used as an additive in numerous food and pharmaceutical products. Basically, they have to satisfy quality requirements, which is the reason why the procedure for their synthesis needs to be optimized in aspects of selection of reactants, their molar ratio, necessary laboratory equipment, reactant addition order, working temperature, isolation of final product from the reaction mixture, yield and product quality. A semi-industrial installation for the production of calcium and sodium citrate will be projected on the basis of the results of this investigation. The importance of this investigation is the fact that these salts are not produced in our country and the entire quantity (about 20 t per year) is imported.
Hydantoins: Synthesis, properties and anticonvulsant activity
Tri?ovi? Nemanja P.,U??umliGordana S.,Petrovi? Slobodan D.
Hemijska Industrija , 2009, DOI: 10.2298/hemind0901017t
Abstract: Hydantoin is a five-membered cyclic ureide that is present in numerous biologically active compounds including antiarrhytmics, anticonvulsants and antitumor agents. This paper describes different ways of synthesis of hydantoin-derivatives, their physical properties and reactivity. Also, the most widely used hydantoin anticonvulsants and the analysis of structureactivity relationships of anticonvulsant drugs in terms of lipophilicity and hydrogen bonding are presented here.
Solvent effects on photodegradation of CI Reactive Orange 16 by simulated solar light
Mijin Du?an ?.,Zlati? Dragana Z.,U??umliGordana S.,Jovan?i? Petar M.
Hemijska Industrija , 2008, DOI: 10.2298/hemind0805275m
Abstract: Organic solvents may appear in wastewaters and other industrial waste streams containing dyes, therefore, their photodegradation catalyzed by TiO2 should be investigated. Solvent effect on photodegradation of CI Reactive Orange 16 has been studied using simulated solar light and P-25 TiO2. Methyl, ethyl and isopropyl alcohol as well as acetone were used as solvents. Photodegradation reaction was faster in methyl than in ethyl alcohol while in water was the slowest. RO16 photodegradation efficiency and reaction rate decreased in the presence of small concentration of ethanol. Higher photodegradation efficiency was observed for higher ethanol concentration. For acetone, photodegradation decreased as concentration of acetone increased. It seems that protic solvents at higher concentrations promote reaction, while at low concentrations slow down reaction. Aprotic solvents slow down reaction.
Azo-hydrazone tautomerism of aryl azo pyridone dyes
Mirkovi? Jelena M.,U??umliGordana S.,Marinkovi? Aleksandar D.,Mijin Du?an ?.
Hemijska Industrija , 2013, DOI: 10.2298/hemind120309053m
Abstract: In the last three or four decades disperse dyes derived from pyridones (in particular azo pyridone dyes) have gained in importance, and are widely used in various fields. These compounds have excellent coloration properties, and are suitable for the dyeing of polyester fabrics. Basic features of these dyes are simplicity of their synthesis by diazotation and azo coupling. They generally have high molar extinction coefficient with medium to high light and wet fastness. The absorption maxima of these dyes show their visible absorption wavelength ranging from yellow to orange, which can be attributed to poorly delocalized electrons in the pyridone ring. However, there are several dyes with deep colors such as red or violet. Pyridone dyes with alkyl and aryl groups in ortho position to azo group show 2-pyridone/2-hydroxypyridine tautomerism, while those containing OH and NHR groups conjugated with the azo group show azo-hydrazone tautomerism. Determining azo-hydrazone tautomerism could be therefore interesting, since the tautomers have different physico-chemical properties and most importantly different coloration. The literature on azo-hydrazone tautomerism, determination of equilibrium position, and investigation of substituent and solvent influence on tautomerism has been summarized in the presented review. The general conclusion is that the equilibrium between two tautomers is influenced by the structure of the compounds and by the solvents used. The tautomeric behavior patterns of the arylazo pyridone dyes in the reviewed literature has been studied using various instrumental techniques, including FT-IR, UV-vis, and NMR spectroscopy. The quantum chemical calculations related to the azo-hydrazon tautomerism have also been included. A large number of pyridone dyes exist in hydrazone form in solid state, while in solvents there is a mixture of tautomers. In addition, the X-ray single-crystal diffraction data analysis of some commercial pyridone dyes has been discussed concluding that they all crystallize in the hydrazone form.
Oxaprozin: Synthesis, SAR study, physico-chemical characteristics and pharmacology
Bo?i? Bojan ?.,Tri?ovi? Nemanja P.,Valenti? Nata?a V.,U??umliGordana S.
Hemijska Industrija , 2011, DOI: 10.2298/hemind110426040b
Abstract: Oxaprozin (3-(4,5-difeniloksazol-2-yl)propanoic acid) is a nonsteroidal anti-inflammatory drug (NSAID) used in the treatment of numerous inflammatory musculoskeletal diseases, including rheumatoid arthritis, osteoarthritis, tendonitis, ankylosing spondylitis and bursitis. It is the first representative member of the diaryl-substituted heterocyclic compounds, which have found clinical use as selective cyclooxygenase-2 (COX-2) inhibitors. U.S. Food and Drug Administration (FDA) approved its official use in 1992. Both anti-inflammatory and analgesic properties of oxaprozin are mainly due to the potent inhibition of COX. However, oxaprozin-induced benefits might be also regulated by other COX-independent pathways. It has been shown that oxaprozin induced direct proapoptotic effects in CD40L-treated human monocytes independently of COX inhibition. It also has several advantages in the treatment of inflammatory diseases in comparison to other NSAIDs such as aspirin, naproxen, indomethacin and phenylbutazone, which enabled oxaprozin to become one of the most used NSAIDs in America. Oxaprozin, as other members of the group of NSAIDs, can cause gastrointestinal complications, but significantly lower due to relatively high pKa value. In this paper, importance of oxaprozin in the treatment of arthritis and its pharmacokinetic properties were described, therewith its activity and side effects were compared with other commercially available anti-inflammatory drugs.
Synthesis of azo pyridone dyes
Mijin Du?an ?.,U??umliGordana S.,Valenti? Nata?a V.,Marinkovi? Aleksandar D.
Hemijska Industrija , 2011, DOI: 10.2298/hemind110428037m
Abstract: Over 50% of all colorants which are used nowdays are azo dyes and pigments, and among them arylazo pyridone dyes (and pigments) have became of interest in last several decades due to the high molar extinction coefficient, and the medium to high light and wet fastness properties. They find application generally as disperse dyes. The importance of disperse dyes increased in the 1970s and 1980s due to the use of polyester and nylon as the main synthetic fibers. Also, disperse dyes were used rapidly since 1970 in inks for the heat-transfer printing of polyester. The main synthetic route for the preparation of azo dyes is coupling reaction between an aromatic diazo compound and a coupling component. Of all dyes manufactured, about 60% are produced by this reaction. Arylazo pyridone dyes can be prepared from pyridone moiety as a coupling component, where substituent can be on nitrogen, and diazonim salts which can be derived from different substituted anilines or other heterocyclic derivatives. In addition, arylazo dyes containing pyridone ring can be prepared from arylazo diketones or arylazo ketoesters (obtained by coupling β-diketones or β-ketoesters with diazonim salts) by condensation with cyanoacetamide. Disazo dyes can be prepared by tetrazotizing a dianiline and coupling it with a pyridone or by diazotizing aniline and coupling it with a dipyridone. Trisazo dyes can be also prepared by diazotizing of aniline and coupling it with a tripyridone or by hexazotizing a trianiline and coupling it with a pyridone. The main goal of this paper is to give a brief review on the synthesis of arylazo pyridone dyes due to the lack of such reviews. In addition, some properties of arylazo pyridone dyes as light fastness and azo-hydrazon tautomerism are disccused.
Optimization of the procedure for the synthesis of calcium lactate pentahydrate in laboratory and semi-industrial conditions
U??umliGordana S.,Tri?ovi? Nemanja P.,?or?evi? Irena N.,Valenti? Nata?a V.
Hemijska Industrija , 2009, DOI: 10.2298/hemind0901011u
Abstract: This paper is concerned on the development of the optimal laboratory procedure for the synthesis of calcium lactate pentahydrate and the application of obtained results in a project for a semi-industrial installation for its production. Calcium lactate is used as an additive in numerous food and pharmaceutical products. Basically, it has to satisfy quality requirements. That was the reason why the procedure for its synthesis had to be optimized in aspects of selection of reactants, their molar ratio, necessary laboratory equipment, reactant addition order, working temperature, isolation of final product from the reaction mixture, yield and product quality. A semi-industrial installation for the production of calcium lactate pentahydrate is projected on the basis of the results of this investigation. The importance of this investigation arises from the fact that this salt is not produced in Serbia and the complete quantity (about 20 t per year) is imported.
Synthesis, structure and solvatochromism of 5-methyl-5-(3- or 4-substituted phenyl)hydantoins
NATALIJA D. DIVJAK,NEBOJ?A R. BANJAC,NATA?A V. VALENTI?,GORDANA S. U??UMLI
Journal of the Serbian Chemical Society , 2009,
Abstract: Several 5-methyl-5-(3- or 4-substituted phenyl)hydantoins were prepared and their ultraviolet absorption spectra were recorded in the region 200–400 nm in twelve solvents of different polarity. The effect of solvent dipo larity/polarizability and solvent/solute hydrogen bonding interactions were analyzed by means of the linear solvation energy relationship (LSER) concept proposed by Kamlet and Taft. The lipophilic activity of the investigated hydantoins was estimated by calculation of log P values with Advanced Chemistry Development Software. The calculated values of log P were correlated with the contribution of hydrogen bond donor–solvent interactions. By employing the thus obtained linear dependence, the pharmacological activity of the studied hydantoin derivatives is discussed.
Solvent effects on the structure-property relationship of anticonvulsant hydantoin derivatives: A solvatochromic analysis
Nemanja Tri?ovi?, Nata?a Valenti?, Gordana U??umli
Chemistry Central Journal , 2011, DOI: 10.1186/1752-153x-5-62
Abstract: Derivatives of hydantoin (imidazolidine-2,4-dione) have been demonstrated to exert various effects on nervous systems, most of which are compatible with an anticonvulsant action. Phenytoin (5,5-diphenylhydantoin, Dilantin?) is one of the oldest non-sedative antiepileptic drugs, which is employed in cases of generalized tonic-clonic seizures (so-called grand mal epilepsy) and focal motor seizures [1]. Mephenytoin (3-methyl-5-ethyl-5-phenylhydantoin, Mesantoin?) has the same spectrum of indications as phenytoin, but its use is limited to the cases unable to tolerate other drugs [2]. Thus, the demethylated metabolite, nirvanol (5-ethyl-5-phenylhydantoin), was the first hydantoin derivative introduced for the treatment of chorea [3]. Due to numerous side effects, its use was soon abandoned. Ethotoin (3-ethyl-5-phenylhydantoin, Peganone?) has a lower anticonvulsant potency than phenytoin and additional hypnotic effects, which limit its clinical use [4].The anticonvulsant action of hydantoin derivatives is due to the selective block of high-frequency neuronal activity [5,6]. The molecular mechanism for this is their binding to the voltage-sensitive sodium channels responsible for the action potential. Phenytoin is suggested to form an array of molecules stacked on a β-turn segment of the proteic part of the putative receptor site, through the formation of hydrogen bonds with the carbonyl group in position 2 and the NH group in position 3 [7]. However, this site on the voltage-sensitive sodium channel is still not completely defined. Compounds with increased selectivity for it may provide significant activity and fewer side effects. Regarding the structural demands, Poupaert et al. [8] observed that the anticonvulsant activity was decreased when the hydrogen bond formation ability of the phenytoin molecule was reduced by altering the hydantoin ring into succinimide and pyrrolidinone and when these rings were N-methylated. This study was expanded by Cortes et al. [9], who o
Page 1 /338696
Display every page Item


Home
Copyright © 2008-2017 Open Access Library. All rights reserved.