Chemistry Journal of Moldova

DOI: https://doi.org/10.19261/cjm.2020.803

Abstract (PDF)

Graphical Abstract: The main scientific achievements of great significance accomplished by Professor Ilie Fishtik at the University of Iowa and the Worcester Polytechnic Institute, in several fields of the physical chemistry as chemical thermodynamics, kinetics and heterogeneous catalysis were revealed and briefly analysed. Fundamental equations of chemical thermodynamics within the De Donder (stoichiometric) approach were reformulated in terms of a special class of chemical reactions, called as response reactions. Using this approach, the unusual behaviour of chemical equilibrium systems, to interpret the apparent contradictions to Le Chatelier principle and to discover hitherto unnoticed thermodynamic identities, was rationalised. The stabilities of chemical species were formulated in terms of a certain class of stoichiometrically unique chemical reactions and their thermochemical characteristics. A completely new approach for the generation and simplification of kinetic mechanisms for complex reaction systems was developed and applied. Based on a new type of reaction networks, referred to as reaction route graphs, a systematic method of analysis and reduction of a microkinetic mechanism was established and employed.

DOI: https://doi.org/10.19261/cjm.2020.778

Abstract (PDF)
Supplementary Material (PDF)

Graphical Abstract: The present work focuses on evaluation of the chemical composition and antioxidant activity of the hydro-methanolic extract of Melissa officinalis from Algeria. The liquid chromatography-mass spectrometry analysis allowed the identification of six compounds: caffeic acid, caftaric acid, hydroxyjasmonic acid glucoside, caftaric acid glucoside, rosmarinic acid and sagerinic acid. The in-vitro antioxidant activity of the hydro-methanolic extract was evaluated by using four different methods including: radical scavenging assay (DPPH), scavenging activity (ABTS), cupric reducing antioxidant capacity, and ferric reducing power assay.  The extract exhibited a relatively strong antioxidant activity compared to the synthetic antioxidants. The highest radical scavenging activity was registered using DPPH and ABTS methods,  IC₅₀= 20.53±2.64 μg/mL and 22.50±0.67 μg/mL, respectively. These results suggest that Melissa officinalis L. could be considered a potential source of natural antioxidants with potential interest in the agrochemical and pharmaceutical industries.


 

DOI: https://doi.org/10.19261/cjm.2020.795

 
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Graphical Abstract: Polysaccharides from the pods of haricot vert (Phaseolus vulgaris L.) were extracted using a simple heating method, by varying extracting temperature, heating time, solid-to-liquid ratio, and solvent compositions. The obtained results were processed using statistical analysis that helped to identify the optimal conditions for the polysaccharides’ extraction process. This study represents a promising production method of bioactive polysaccharides extract in the food and pharmaceutical industry.   

 

DOI: https://doi.org/10.19261/cjm.2020.775

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Graphical Abstract: This paper presents the development and optimization of a new approach which combines the utilization of activated carbon and glucose oxidase enzyme for decolourisation of beet sugar syrup. The combining of the physical adsorption with the enzymatic reaction was managed to improve the decolourisation of beet sugar syrup from 35.29 to 83.68% compared to the basic adsorption by activated carbon after 120 min of operation under the optimum conditions. The maximum decolourisation efficiency by the coupled process was achieved at glucose oxidase dosage of 0.07 g, glucose concentration of 20 mM, and solution pH 7 at the temperature of 30ºC using 0.01 g of activated carbon particles. Given the high effectiveness, reusability, and the eco-friendly nature of the process, the proposed method can serve as an alternative to ordinary decoloursation techniques.



 

DOI: https://doi.org/10.19261/cjm.2020.791

Abstract (PDF)
Graphical Abstract: The present paper reports the results of microwave irradiation assisted method for the preparation of bicyclohomofarnesenic methyl esters versus classical Stoll and Hinder method. Moreover, the chemical transformations of bicyclohomofarnesenic methyl esters via anodic electrooxidation and dye-sensitized photooxidation were performed. A new method for the preparation of methyl 7-oxo-13,14,15,16-tetranorlabd-6,8(8)-dien-12-oate and the mechanism of electrochemical products formation are presented. The structure of all synthesized compounds was fully confirmed by spectral methods.


 

DOI: https://doi.org/10.19261/cjm.2020.774

Abstract (PDF)
Graphical Abstract: The present paper shows that lanthanum(III) nitrate hexahydrate can be used as mild and environment friendly homogeneous catalyst for an efficient one-pot multi-component synthesis of biologically active 1,8-dioxo-octahydroxanthene and 14H-dibenzo[a,j]xanthene derivatives. The solvent free condensation reaction of aromatic aldehydes and dimedone or β-naphthol was carried out at 70-80ºC during 10-30 min. The advantages of this eco-friendly synthesis route are numerous, and include the use of an inexpensive catalyst, high to excellent yield, short reaction time and high catalytic activity that can make this method an interesting alternative to multi-step approaches.


 

 

 

DOI: https://doi.org/10.19261/cjm.2020.751

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Graphical Abstract: The aim of this research work was to evaluate the pollution level of phosphorus, sulphur and nitrogen in the former manufacturing areas (the former Kuprava drainage pipe factory and landfill site) and compare it with the Sita forest area levels using lichens as bioindicators. Additionally, the correlation between the content of these elements in lichens and soil was examined. The research results show that in the former drainage pipe factory area and landfill site, the levels of phosphorus, sulphur and nitrogen content were elevated in comparison with Sita forest. In the case of phosphorus and nitrogen contents, a positive correlation was observed between soil and lichen samples. 


 

DOI: https://doi.org/10.19261/cjm.2020.695   

Abstract (PDF) 

Graphical Abstract: The research is devoted to the study of unexpected products that formed as a result of the condensation reaction between 2-acetylpyridine and 2-formylpyridine under the Claisen-Schmidt reaction conditions. As a result, a sequence of reactions leading to the following compounds has been proposed: 1,3-bis (pyridin-2-yl) prop-2-en-1-one (3); 1,3,5-tri (pyridin-2-yl) pentane-1,5-dione (4); (2,4-dihydroxy-2,4,6-tri(pyridin-2-yl)cyclohexyl)(pyridin-2-yl)methanone (5) and (4-hydroxy-2,4,6-tri(pyridin-2-yl)cyclohexane-1,3-diyl)bis(pyridin-2-ylmethanone) (6) as well as 2-formylpyridine (1) and 2-acetylpyridine (2). The plausible mechanism of these chemical transformations has been proposed. All the obtained compounds demonstrate moderate antimicrobial, antifungal and antioxidant activity.


 

DOI: https://doi.org/10.19261/cjm.2020.718

Abstract (PDF)

Graphical Abstract: The application of a new hydrometallurgical process for gold extraction by thiosulphate leaching from Romanian mining wastes, coming from Balan and Deva deposits, was studied. There was obtained 85% of Au extraction after leaching; moreover, an integrated flow-sheet, including recycling of process solution and carbon, was outlined, based on results obtained at a laboratory scale, using a schematic chemical circuit of treatment. Global recovery of the process (leaching-adsorption-desorption-electrodeposition) of about 75-80% of Au was achieved. The developed integrated flow-sheet, allows to recycle the reagents during the process, with a loss of only 5-10%, in particular thiosulphate and alcohol, for each complete circuit of treatment.