Browsing by Author "Kheffache, Djaffar"
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Item A computational study of the main degradation product of antitumor drug imexon(World Scientific Publishing Co. Pte Ltd, 2017) Kheffache, Djaffar; Ouamerali, OuridaWe theoretically study, from the thermodynamic point of view, the possibility of the two degradation pathways of antitumor drug of imexon. According to the theoretical results obtained at DFT level in both gas and aqueous phases, the two degradation pathways of imexon are characterized by negative reaction Gibbs free energies. It has been found that 4-imino-5-methylene-imidazolidin-2-one is the favored degradation product of imexon. Herein, the focus of this work has been on calculating the geometries, relative energies and electronic properties of all possible prototropic tautomers of 4-imino-5-methylene-imidazolidin-2-one using the DFT and MP2 levels. The bulk water environment has been simulated by continuum model using Solvation Model based on Density (SMD). The UV spectra of two dominant tautomers of 4-imino-5-methylene-imidazolidin-2-one are also predicted using time-dependent density functional theory and the results are compared with the available experimental data. The comparison of the simulated and the experimental absorption spectra has allowed us to accurately characterize the predominant tautomer of the degradation product in aqueous mediumItem Conformational analysis and intramolecular hydrogen bonding of cis-3-aminoindan-1-o l : a quantum chemical study(Springer, 2013) Kheffache, Djaffar; Guemmour, Hind; Dekhira, Azzedine; Benaboura, Ahmed; Ouamerali, OuridaItem Conformational and NMR analysis on cis 1,3-indanediol(Elsevier, 2011) Guemmour, Hind; Kheffache, Djaffar; Benaboura, AhmedItem Polycopié de cours : methodes spectroscopiques d’analyse : Cours destiné aux étudiants de 3ème année « Licence Chimie Analytique »(Université M’hamed Bougara de Boumerdes : Faculté des Sciences : Département de Chimie, 2023) Kheffache, DjaffarCe document pédagogique a été spécialement conçu pour les étudiants de troisième année de licence ainsi que pour les étudiants de master M1 dans la spécialité de la chimie analytique. Il présente les principes fondamentaux des méthodes spectroscopiques d'analyse largement utilisées par les professionnels de la chimie. Dans ce polycopié, nous avons veillé à détailler les principes fondamentaux de la spectroscopie de manière générale, en mettant l'accent sur trois techniques spécifiques : la spectro.......Item Some physicochemical properties of the antitumor drug thiotepa and its metabolite tepa as obtained by density functional theory (DFT) calculations(Springer, 2010) Kheffache, Djaffar; Ouamerali, OuridaItem Sustainable starch-based bioplastics reinforced with carob filler: characterization and biodegradability assessments(Taylor and Francis Ltd., 2024) Guemmour, Hind; Kheffache, Djaffar; Khier, NawalStarch-based thermoplastic polymer is a biopolymer that is being widely explored as a replacement for conventional polymers. Since thermoplastic starch suffers from mechanical defects, certain mechanical and thermal properties of starch-based polymers can be improved by incorporating fillers or reinforcements derived mainly from natural substances. This article reports the preparation, physicochemical, and mechanical characterization and biodegradation of starch-based bioplastics extracted from potato (Solanum tuberosum) peels using glycerol (G) as plasticizer and reinforced with carob powder, a readily growing plant in Mediterranean climates. The present study investigates the effect of incorporating different proportions (0, 2, 5, 10, and 15 wt.%) of carob powder (Cb) in the films thus prepared. These biopolymer films were fully characterized using analytical techniques including Fourier transform infrared spectroscopy with attenuated total reflection (FTIR/ATR), thermogravimetric analysis (TGA/DTG), X-ray diffraction (XRD), optical microscopy (OM), Scanning electron microscopy (SEM), mechanical evaluations, and biodegradability assessments. The biodegradability of the obtained bioplastic samples was evaluated. Scanning electron microscopy (SEM) revealed strong interfacial adhesion between the constituent filler and the polymer matrix.Item Theoretical investigation of the self-association of antitumor drug imexon(Springer, 2020) Guemmour, Hind; Kheffache, DjaffarThe dimers resulting from self-association of oxo-imino, oxo-amino, and hydroxyl-imino tautomers of imexon, that present two hydrogen bonds, were fully optimized with the density functional methods B3LYP, M06-2X in conjunction with 6-311++G(d,p) basis set. Additionally, second-order Møller-Plesset (MP2) level in combination with 6-311++G(d,p) basis set was employed for comparison purpose. The thermodynamic stability of the self assembled structures in gaseous phase has been obtained according to the analyses of total electronic energies and hydrogen bonding interactions. The bulk water environment has been simulated using the universal solvation model based on solute electron density (SMD). Stability and structure of homochiral and heterochiral imexon dimers resulting from the three imexon tautomers have been carried out to investigate the chiral discrimination. The imexon dimer with heterochiral configuration resulting from self-assembling oxo-amino tautomer is found to be thermodynamically most stable in both gas and aqueous phases. The interaction energies for these self assembled structures were further evaluated with the basis set superposition error corrections. The so-called seven-point interaction energy which includes corrections for BSSE and deformation was calculated. The intermolecular interactions of the selected dimers have been analyzed by calculation of electron density (ρ) and Laplacian (∇2ρ) at the bond critical points (BCPs) using atoms-in-molecule (AIM) theory.Item Vinyl acetate Semi-Continuous emulsion terpolymerization with butyl acrylate and 2-Ethyl hexyl acrylate monomers(Springer, 2021) Guemmour, Hind; Kheffache, DjaffarIn this article we report preparation, physico-chemical and mechanical characterization of poly (vinyl acetate) (PAVc) fi lms resulting from the copolymerization of vinyl acetate (VAc) with two acrylate monomers, butyl acrylate (BuA) and 2‐ethyl hexyl acrylate (2-EHA) via emulsion polymerization method. Vinyl acetate (VAc) was used as principal monomer and copolymerized with butyl acrylate (BuA) and 2‐ethyl hexyl acrylate (2-EHA) at the feeding ratio of 85/15/0, 85/0/15, 85/5/10, 85/10/5, 85/7.5/7.5 wt % of VAc/BuA/2-EHA using deionised water as dispersion medium. The semi-continuous emulsion polymerization was carried out in the presence of potassium persulfate used as free radical initiator, two emulsifiers, anionic and non-ionic surfactants and hydroxyethyl cellulose (HEC) used as a protective colloidal. The obtained copolymers were further analysed by Brookfi eld viscosimeter, Fourier transform infrared spectroscopy (FTIR/ATR), thermogravimetric analysis (TGA/DTG), scanning electron microscopy (SEM) and mechanical tests. The infl uence of composition on thermal characteristics of the obtained fi lms is describedItem What is the real existing form of imexon? - Quantum chemical studies(Elsevier, 2010) Kheffache, Djaffar; Ouamerali, O.