Chemistry Journal of Moldova. General, Industrial and Ecological Chemistry

7-12

Authors: Anatoli Cartasev, Valeriu Rudic

The purpose of this research was to investigate the impact of indigenous starter culture capable to synthesize exopolysaccharides (EPSs) on physicochemical properties of yoghurt. Two starter cultures, EPS-producing and non-EPS-producing, were developed from the autochthonous lactic acid bacteria strains by pairwise combining Lactobacillus delbrueckii ssp. bulgaricus and Streptococcus thermophilus strains. In the present study the ropy strain of Streptococcus thermophilus CNMN LB-50 was incorporated in EPS-producing starter culture. The microstructure, viscosity, EPS amount,structural properties and syneresis of yoghurt samples were assessed. It has been established that the EPS-producing starter culture provided a reduction of structural degradation and increased degree of structural recovery after deformation. Besides, it was observed that the use of EPS synthesized starter culture in yoghurt production restrains the syneresis of the gel.

19-27

Authors: Rodica Mariana Diaconescu, Carmen Zaharia

The paper proposes an artificial neural network (ANN) model of multilayers perceptron type (MLP3:10:1) adapted for mechanical-chemical treatment system of an industrial effluent (i.e. coagulation-flocculation - sedimentation applied for an industrial effluent produced in a manufacturing plant of bricks and other ceramic products). This model of multiple inputs-one single output considers three input variables (independent variables) like the temperature (z1), dose of polyelectrolyte (z2) and agitation time (z3) and one single output variable (dependent variable) as the removal of turbidity (Y1) or colour (Y2). Consequently, the proposed ANN model is optimized and also tested for some data from outside of the training experimental field. The optimal removal of turbidity (91.7%) is performed working at a temperature of 20°C, with a polyelectrolyte dose of 20 mg/L, for 30 min of agitation at 50 rpm, and in the case of optimal colour removal (92.2%) by working at a temperature of 26°C, with a polyelectrolyte dose of 15 mg/L, for no more than 30 min of agitation at 50 rpm, respectively.

34-40

Authors: Masahiro Mikuriya, Iyo Matsushima, Daisuke Yoshioka

Mixed-valent trinuclear manganese complex with N,N’-bis(2-hydroxy-3,5-dimethylbenzylN,N’-dimethyl-1,2-ethanediamine (H2hdde), [Mn3(hdde)2(CH3CO2)2(CH3O)2], was synthesized. The X-ray crystal structure analysis revealed that compound is a trinuclear manganese complex with linearly arrangement of MnIII-MnII-MnIII, where two manganese ions of each MnII -MnIII pair are bridged by µ-phenolato-oxygen of hdde2– ligand, µ-methanolato-oxygen, and µ-acetato ion. Temperature dependence of magnetic susceptibilities showed an increase of magnetic moment as the temperature lowers in the range of 300—6 K and a decrease below 6 K. The magnetic analysis based on Heisenberg model yielded ferromagnetic coupling (J = 2.62 cm–1) between MnIII and MnII ions.

50-57

Authors: Nassiba Fekhar, Hocine Boutoumi, Mohamed Krea, Saâd Moulay, Drioueche Asma, Zoubir Benmaamar

Essential oils were extracted from Artemisia herba-alba L. and Ruta montana L. by means of steam distillation and thionated with a reagent combination of phosphorus pentasulfide and sodium bicarbonate. Both parent essential oils and their modified ones were screened for their biological and insecticidal activities. The results showed that essential oils were composed mainly of ketones; essential oils from Artemisia herba-alba L. and those from Ruta montana L. consisted of bicyclic monoterpenes and acyclic aliphatic ketones (thujone, camphor and 2-undecanone), respectively. The antimicrobial activity of essential oils was substantially improved upon thionation (from 10 to 34 mm and from 11 to 32 mm). The insecticidal effect of the thionated essential oil from Ruta montana L. was observed to be very significant, but that of the essential oil from Artemisia herba-alba L. was observed to decrease (from 100% to 70% after 24 h). The extracted essential oils as well as their thionated forms were characterized by GC-MS, FT-IR, and UV-visible

64-70

Authors: Emre Topal, Gökhan Gece

The topic of corrosion inhibition of different metals by organic compounds has been the focus of intense scrutiny for decades. The enormity of the problem is reflected in the need to understand the underlying inhibition mechanisms of such compounds, one of which is the class of aliphatic amines. Electrochemical measurements represent protective effect of these compounds at ever-increasing levels of detail but these methods lack the resolution to represent inhibition efficiency-molecular structure relations adequately. In this study, the dependence of inhibition effect of four aliphatic amines (methylamine, ethylamine, n-propylamine, and n-butylamine), on their molecular and electronic structure is analysed using quantum chemical calculations. The obtained results of these calculations were found to be consistent with the experimental findings.

79-86

Authors: Oksana Dudarko, Yuriy Zub

The direct template method was used for the synthesis of mesoporous organosilica sorbents of SBA-15 type with phosphonic acid groups using sodium metasilicate (SS) as a source of silica. The presence of functional groups in the synthesized samples was confirmed by IR spectroscopy and elemental analysis. It was demonstrated that the increasing concentration of phosphorous-containing groups influenced the morphology and the spatial order of the porous structure of the samples. However, ordered mesoporous conglomerates can be identified in the resulting materials even when the content of functionalized phosphorus-containing silane in the reaction mixture is 33%. This approach allowed producing relatively cheap materials with ordered structure, developed specific surface (550-700 m2 /g) and high sorption volume (0.74-0.81 cm3 /g). The optimal sodium metasilicate (SS) : diphosphoethyltriethoxysilane DPTS) ratio for the synthesis of SBA-15 type organosilicas with phosphonic acid residues was found to be 10:2.

102-108

Authors: Ecaterina Tocana, Anatolii Siminel, Lilia Croitor

Two new mononuclear coordination complexes constructed by non-covalent interactions,[Ni(phen)2(H2O)2](ClO4)2 (1) and [Cd(ClO4)2(phen)2] (2), where phen=1,10-phenanthroline, were synthesized and characterized by single-crystal X-ray diffractometry. The structural determination revealed that the coordination geometry around the Ni/Cd centres is distorted octahedral for each complex. In the complexes 1 and 2 the metal atoms have N4O2 coordination cores. In 1 the intermolecular OH···O hydrogen bonds, which involve the coordinating water molecules as donors and the perchlorate O atoms as acceptors form zigzag-like hydrogen-bonding chains, which are further assembled via π-π stacking interactions between adjacent phen rings, thus forming a supramolecular network structure. In the crystal structure of 2, π–π stacking interactions are noted between neighbouring hydrophobic phen ligands, yielding 1D supramolecular chains. The luminescence studies show that compound 1 displays blue luminescence, while compound 2 – white-light emission upon excitation with ultraviolet light.