Chemical Papers- Slovak Academy of Sciences (CHEM PAP)

Publications in this journal

• Article: Aqueous foam stabilized by polyoxyethylene dodecyl ether

  Xi-An Li, Jian-Bing Peng, Yong-Li Yan
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  ABSTRACT: Foaming properties of aqueous solutions of the nonionic surfactant polyoxyethylene dodecyl ether (C12EO n ) were studied at 298 K. Four different EO chain lengths, namely C12EO3, C12EO5, C12EO7, and C12EO9, were considered. The foams obtained from C12EO3 or C12EO5 were extraordinary stable retaining a constant volume for more than 20 h. The presence of lamellar liquid crystalline phases was mainly responsible for the super-stable aqueous foams.
  Chemical Papers- Slovak Academy of Sciences 02/2013; 63(5):620-624.
• Article: Flexibility of active-site gorge aromatic residues and non-gorge aromatic residues in acetylcholinesterase

  Pavan K. GhattyVenkataKrishna, Neelima Chavali, Edward C. Uberbacher
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  ABSTRACT: The presence of an unusually large number of aromatic residues in the active site gorge of acetylcholinesterase is a subject of great interest. Flexibility of these residues has been suspected to be a key player in controlling the ligand traversal in the gorge. This raises the question of whether the over-representation of aromatic residues in the gorge implies higher-than-normal flexibility of these residues. The current study suggests that it does not. Large changes in the hydrophobic cross-sectional area due to dihedral oscillations are probably the reason of their presence in the gorge.
  Chemical Papers- Slovak Academy of Sciences 01/2013;
• Article: Role of interfacial chemistry on the rheology and thermo-mechanical properties of clay-polymer nanocomposites for building applications

  Hieu-Thao Huynh, Karim Benzarti, Myriam Duc
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  ABSTRACT: This study is directed towards investigating the role of the surface treatment of clay particles on the rheological and thermomechanical behaviour of clay-epoxy blends. Nanocomposites were prepared by mixing small amounts (5-10 mass %) of commercial organoclays or raw clays with an epoxy system commonly used in civil engineering. Rheological characterisations in the liquid state revealed a pronounced thixotropic character of the organoclay-based systems, which all exhibited a shear-thinning behaviour above a critical stress threshold (yield stress), depending on both the intensity of interfacial interactions and the degree of filler dispersion. On the other hand, systems based on raw clay particles behaved like Newtonian fluids, in the same way as the unreinforced polymer matrix. Complementary dynamic mechanical analyses (DMA) performed on the cured cross-linked nanocomposites also showed significant changes in the viscoelastic behaviour of the epoxy matrix due to the introduction of organoclays, whereas only minor variations were observed following the introduction of raw fillers. These results were consistent with nanoscale morphological characterisations performed by conventional X-ray diffraction (XRD) on the various hybrid systems. In this context, rheology and DMA appear as attractive alternative methods for assessing the filler dispersion at a macroscopic (and possibly more relevant) scale. This research is of practical interest for civil engineers, since clay reinforced-epoxies could in the future be used as coating materials with enhanced barrier performances, in order to protect infrastructures against environmental ageing or corrosion. (C) 2011 Institute of Chemistry, Slovak Academy of Sciences
  Chemical Papers- Slovak Academy of Sciences 06/2012; 66(5):519-531.
• Article: 2-Alkylsulphanyl-4-pyridinecarbothioamides — inhibitors of oxygen evolution in freshwater alga Chlorella vulgaris

  Katarína Kráľová, František Šeršeň, Věra Klimešová, Karel Waisser
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  ABSTRACT: The inhibition of the oxygen evolution rate (OER) in Chlorella vulgaris by 2-alkylsulphanyl-4-pyridinecarbothioamides (APCTs; alkyl = methyl up to hexadecyl) was studied. APCTs were found to inhibit photosynthetic electron transport (PET) which resulted in the inhibition of OER in algae. The inhibitory activity of APCTs was highly dependent on the alkyl chain length of the 2-alkylsulphanyl substituent and the corresponding dependence showed a bilinear course with the decyl derivative as being the most active inhibitor. Using EPR spectroscopy, the site of APCT action in the algal photosynthetic apparatus was determined. It was confirmed that APCT interacted mainly with the D. intermediate, i.e. with tyrosine radical (TyrD) occurring at the 161st position in D2 protein which is situated on the donor side of photosystem 2. Keywordsalkyl length– Chlorella vulgaris –EPR spectroscopy–photosynthetic electron transport–inhibition–oxygen electrode
  Chemical Papers- Slovak Academy of Sciences 05/2012; 65(6):909-912.
• Article: A procedure for the determination of dichloromethane and tetrachloroethene in water using pervaporation and gas chromatography

  Irena Rutkiewicz, Wojciech Kujawski, Jacek Namieśnik
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  ABSTRACT: In the present study, pervaporation was applied to the determination of tetrachloroethene (PCE) and dichloromethane (DCM) in liquid samples. PCE is the most commonly used solvent in drycleaning processes. PCE belongs to group 2A of carcinogens (probably carcinogenic to humans) according to the classification of the International Agency for Research on Cancer (IARC). DCM is also widely used as an industrial solvent for the purification and isolation of intermediates or products. DCM is classified as a “possible” human carcinogen by the IARC. The aim of this study was to evaluate a new procedure for the determination of DCM and PCE in liquid samples based on the pervaporative removal of DCM and PCE from liquid samples as an analyte isolation/enrichment technique, followed by a direct aqueous injection of the extracts onto the column of a gas chromatograph equipped with an electron capture detector (DAI-GC-ECD). The basic parameters of the new PV-DAI-GC-ECD procedure were evaluated. Keywordspervaporation–dichloromethane–tetrachloroethene–validation
  Chemical Papers- Slovak Academy of Sciences 05/2012; 65(5):578-583.
• Article: Spectroscopic and magnetic evidence of coordination properties of bioactive diethyl (pyridin-4-ylmethyl)phosphate ligand with chloride transition-metal ions

  Urszula Kalinowska-Lis, Bogumiła Żurowska, Justyn Ochocki
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  ABSTRACT: A series of five chloride coordination compounds of diethyl (pyridin-4-ylmethyl)phosphate (4-pmOpe) ligand, i.e. [CuCl2(4-pmOpe)2], [NiCl2(4-pmOpe)4], [CoCl2(4-pmOpe)], [ZnCl2(4-pmOpe)2], and [CdCl2(4-pmOpe)2], was prepared and studied. Stoichiometry and stereochemistry of the compounds was confirmed by spectroscopic and magnetic studies as well as by elemental analyses. The 4-pmOpe ligand has a capacity to coordinate to metal ions by means of phosphoryl oxygen and/or nitrogen of pyridine atoms. In Cu(II), Ni(II), and Zn(II) compounds, 4-pmOpe adopts the monodentate coordination mode, bonding metal centers through the pyridine nitrogen atom only. On the contrary, in Co(II) and Cd(II) compounds, 4-pmOpe acts as N,O-bridging ligand forming polynuclear structures. Magnetic studies (1.8–300 K) indicate mononuclear structure of the Co(II) and Ni(II) compounds and suggest existence of a very weak exchange coupling between metal centers in crystal lattice. Keywordstransition-metal(II) complexes– N-heterocyclic phosphate–spectroscopy–magnetism
  Chemical Papers- Slovak Academy of Sciences 05/2012; 65(5):660-666.
• Article: Synthesis and crystal and molecular structures of N,N′-methylenedipyridinium tetrachlorozincate(II) and N,N′-methylenedipyridinium tetrachlorocadmate(II)

  Mahmoud M. Al-Ktaifani, Mwaffak K. Rukiah
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  ABSTRACT: Treatment of N,N′-methylenedipyridinium dichloride [C5H5N-CH2-NC5H5]Cl2 with MCl2 (M = Zn or Cd) in aqueous solution gives the organic-inorganic hybrid ionic compounds [C5H5N-CH2-NC5H5] · [MCl4]. Both complex salts were fully characterised by multinuclear NMR spectroscopy, elemental analysis, and their molecular structures confirmed by powder X-ray diffraction studies. The most striking feature in both solid state structures was the presence of the C…Cl-M short contacts between the organic [C5H5N-CH2-NC5H5] dication and inorganic [MCl4] anion, which led to different crystal packing. For [C5H5N-CH2-NC5H5]·[ZnCl4], the C…Cl-Zn interactions led to the alternating arrangement of [C5H5N-CH2-NC5H5]2+[ZnCl4]2− to form 1-D chains in the direction [010], and each individual chain had a two-fold rotational axis along the b axis, while for [C5H5N-CH2-NC5H5] · [CdCl4] the C…Cl-Cd associations gave 2-D network. In both solid state structures, the presence of Cl-ring centroid distances gave a strong indication of some form of Cl-π interactions. Keywordsorganic-inorganic hybrid salt– N,N′-methylenedipyridinium–Zn–Cd complex–NMR–powder X-ray diffraction
  Chemical Papers- Slovak Academy of Sciences 05/2012; 65(4):469-476.
• Article: Application of extended NRTL equation for ternary liquid-liquid and vapor-liquid-liquid equilibria description

  Pavol Steltenpohl, Elena Graczová
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  ABSTRACT: Simulation of a hydrocarbons mixture separation by extractive distillation was based on binary vapor-liquid as well as liquid-liquid equilibrium data. Sulfolane was considered as extractive solvent for the selective toluene separation from a model mixture with heptane. For simulation of the chosen hydrocarbons mixture separation in the presence of an extractive solvent, the NRTL model was considered. A set of temperature-dependent binary NRTL parameters was evaluated independently by fitting the experimental vapor-liquid and liquid-liquid equilibrium data of the respective binary subsystems. In order to improve the description of the ternary vapor-liquid equilibrium, original NRTL model extended by the ternary contribution term was used. Parameters of the ternary contribution were obtained by direct fitting of available ternary liquid-liquid equilibrium data while employing the original binary NRTL parameters. Quality of the ternary vapor-liquid-liquid equilibrium description using the original and the extended excess Gibbs energy models was assessed by comparing the calculated compositions of conjugate liquid phases with experimental data. Using the extended NRTL model, mean deviation of the computed mole fractions decreased by approximately four times (9.73 × 10−3) compared to the value obtained using the original NRTL model. Both original and extended NRTL models were employed for the simulation of a model mixture separation by extractive distillation. At chosen experimental conditions, high purity distillate (x 1 > 0.999) was obtained. Results of the aromatics extractive distillation in the presence of sulfolane were compared to those obtained with N-methylpyrrolidone as the extractive solvent. Keywordsvapor-liquid-liquid equilibrium-ternary contribution-extractive distillation-simulation-sulfolane- N-methylpyrrolidone
  Chemical Papers- Slovak Academy of Sciences 05/2012; 64(3):310-317.
• Article: Calcined Ni—Al layered double hydroxide as a catalyst for total oxidation of volatile organic compounds: Effect of precursor crystallinity

  Z. Mikulová, P. Čuba, J. Balabánová, T. Rojka, F. Kovanda, K. Jirátová
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  ABSTRACT: The effect of hydrothermal treatment on properties (crystallinity, porous structure, reducibility, acidity, basicity, and catalytic activity and selectivity in toluene and ethanol total oxidation) of Ni—Al layered double hydroxide precursors and related mixed oxides was examined. The hydrothermal treatment increased considerably both the content of crystalline phase and LDH crystallite size. On the other hand, only a slight effect of the precursor hydrothermal treatment on crystallinity of the related Ni—Al mixed oxides obtained by calcination at 450°C was observed. The reducibility of NiO particles appeared to be hindered considerably compared to the reducibility of pure NiO. Catalytic activity of the Ni—Al mixed oxides prepared from the precursors hydrothermally treated for a short time (4 h) was the highest. The highest amount of acetaldehyde formed during the total oxidation of ethanol, i.e. the worst selectivity was found for the calcined Ni—Al LDH without hydrothermal treatment.
  Chemical Papers- Slovak Academy of Sciences 05/2012; 61(2):103-109.
• Article: Synthesis and reactions of 2-and 4-substituted furo[3,2-c]pyridines

  M. Búdová, K. Fojtíková, J. Miklovič, V. Mrázová, B. Horváth, A. Krutošíková
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  ABSTRACT: Substituted furopropenoic acids were prepared from appropriate aldehyde under the Doebner’s conditions. Obtained acids were converted to the corresponding azides, which were cyclized by heating in Dowtherm to furopyridones. These compounds were aromatized with phosphorus oxychloride to chloro derivatives of furo[3,2-c]pyridine (Va, Vb). Chloro derivative Vb was reduced with hydrazine hydrate to 2-(4-aminophenyl)furo[3,2-c]pyridine in ethanol and Pd/C as a catalyst. Chloro derivative Va was converted to 4-amino-2-(3-pyridyl)furo[3,2-c]pyridine under the same conditions. The chlorine atom in other chloro derivatives (VIIa, VIIb) was replaced by nucleophilic substitution with alkoxides (sodium ethoxide, propoxide, and isopropoxide) and the corresponding alkoxy derivatives were formed. By reaction of VII with cyclic secondary amines (morpholine, piperidine, and pyrrolidine) 4-substituted furopyridines were prepared.
  Chemical Papers- Slovak Academy of Sciences 05/2012; 60(3):231-236.
• Article: Synthetic approaches towards bisspiro[naphthalene-2(1H),3′-(3H)pyrazol]-1-one-containing compounds

  A. S. Girgis, F. H. Osman, F. A. El-Samahy, I. S. Ahmed-Farag
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  ABSTRACT: 1,3-Dipolar cycloaddition reaction of bis{[4-(3,4-dihydro-(2H)-naphthalen-1-oxo-2-yl)methyl-idenephenyl]oxy}alkanes with nitrilimines (generated in situ by triethylamine dehydrohalogenation of the corresponding hydrazonoyl chlorides) in refluxing dry benzene afforded a mixture of monocycloadduct and dicycloadduct products in high regioselectivity. On the other hand, reaction of bis{[2-(3,4-dihydro-(2H)-naphthalen-1-oxo-2-yl)methylidenephenyl]oxy}alkanes with nitrilimines gave the corresponding dicycloadducts as the only isolable regioisomers.
  Chemical Papers- Slovak Academy of Sciences 05/2012; 60(3):237-242.
• Article: Wall effects on terminal falling velocity of spherical particles moving in a Carreau model fluid

  Jaroslav Strnadel, Miloslav Simon, Ivan Machač
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  ABSTRACT: Experimental verification of our previous numerical simulation of wall effects on the terminal falling velocity of spherical particles moving slowly along the axis of a cylindrical vessel filled with a Carreau model fluid is presented. Dependences of the wall correction factor F W on the sphere to tube ratio d/D and on the dimensionless Carreau model parameters m, Λ, and η r were obtained using a finite element method. Calculated data of the wall correction factor were compared with the results of our new falling sphere experiments. The experiments were carried out in six types of cylindrical Perspex columns (16 mm, 21 mm, 26 mm, 34 mm, 40 mm, and 90 mm in diameter) filled with aqueous solutions of polymers exhibiting different degrees of shear thinning and elasticity. Seventeen types of spherical particles (1–8 mm in diameter) made of glass, ceramics, steel, lead, and tungsten carbide were used for the drop tests. Measurements of the liquid flow curves, primary normal stress differences, oscillatory, creep and recovery, stress relaxation, and stress growth tests were carried out on the rheometer Haake MARS (Thermo Scientific). A good agreement between numerically and experimentally obtained F W data was found. Keywordswall effects–sphere free fall–drag coefficient–Carreau viscosity model
  Chemical Papers- Slovak Academy of Sciences 05/2012; 65(2):177-184.
• Article: Effect of cyclodextrins on pH-induced conformational transition of poly(methacrylic acid)

  Jiří Horský, Jiří Podešva, Zuzana Walterová
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  ABSTRACT: A pH-induced conformational transition of atactic poly(2-methylprop-2-enoic acid) (poly(methacrylic acid), PMMA) from the contracted to expanded conformation was investigated by viscometry, potentiometric titration, and anthracene solubilisation in the presence of low-molecular-mass non-ionogenic co-solutes-glucose, α-cyclodextrin (αCD), and γ-cyclodextrin (γCD), respectively. No effect of glucose and αCD on the conformational transition was observed with either of the methods used. On the other hand, the characteristic features of the conformational transition were absent in the presence of γCD. The different effects of the co-solutes indicate that the interaction between PMAA and γCD corresponds to the partial inclusion of the PMAA chain into the γCD cavity. The viscometry and anthracene solubilisation imply that γCD promotes the expanded conformation of PMAA at low pH. The potentiometric titration does not support this conclusion. Even though there is no break on the Henderson-Hasselbalch plot, a characteristic of the conformational transition, the potentiometric behaviour corresponds to that of the contracted PMMA conformation. Thus the results suggest the hierarchical picture of the PMAA conformation at low pH in which the local arrangement of the PMAA chain is a prerequisite for clustering on a larger scale. Keywordscyclodextrins–inclusion complexes–polyelectrolytes–supramolecular structures–conformational transition
  Chemical Papers- Slovak Academy of Sciences 05/2012; 65(6):847-854.
• Article: Methylprednisolone release from agar-Carbomer-based hydrogel: a promising tool for local drug delivery

  Filippo Rossi, Tommaso Casalini, Marco Santoro, Andrea Mele, Giuseppe Perale
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  ABSTRACT: A number of studies and works in drug delivery literature are focused on the understanding and modelling of transport phenomena, the pivotal point of a good scaffold design for tissue engineering. Accurate knowledge of the diffusion coefficient of an active drug plays a key role in the analysis, prediction of their kinetics and formulation of efficient drug delivery systems. In this work, the kinetics of the release of methylprednisolone from agar-Carbomer hydrogel were studied taking into consideration the different drug concentrations and clearances typically achieved in in vitro or in vivo tests. Starting from the experiments it is possible to model the transport phenomenon and to calculate the diffusion coefficient through the hydrogel matrix. Keywordsbiomaterials–diffusion–drug delivery–hydrogel–methylprednisolone
  Chemical Papers- Slovak Academy of Sciences 05/2012; 65(6):903-908.
• Article: Silicon-based thiourea-mediated and microwave-assisted thio-Michael addition under solvent-free reaction conditions

  Kamalakannan Prabakaran, Machindra Gund, Tae Kyu Kim, Euh Duck Jeong, Chae Young Oh, Fazlur-Rahman Nawaz Khan, Jong Sung Jin
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  ABSTRACT: Silicon-based thiourea (SiliaBond® Thiourea) (Si-THU), a heterogeneous catalyst, has been applied to the highly selective C-S bond formation via Michael addition of thiols to α,β-unsaturated carbonyl compounds under solvent-free conditions at 55–60°C. The thio-Michael addition products were obtained in an excellent yield under optimised conditions. This methodology involving a metal-free as well as a metal scavenger catalyst has been found to be an alternative method for the thio-Michael addition reaction. KeywordsSiliaBond® Thiourea–solvent-free Michael reaction–thioethers
  Chemical Papers- Slovak Academy of Sciences 05/2012; 65(5):707-713.