Volume 3 (2002)
Articles
SYNTHESES D'HETEROCYCLES AZOTES ET SOUFRES VIA LES 5-ARYLIMINO-4-CHLORO-5H-1,2,3-DITHIAZOLES ISSUS DE LA CONDENSATION D'AMINES AROMATIQUES AVEC LE SEL D'APPEL
VALÉRIE THIÉRY, BESSON THIERRY *
Reaction of 4,5-dichloro-1,2,3-dithiazolium chloride 1 (Appel salt) with primary aromatic amines allows access to N-arylimino-1,2,3-dithiazoles 2 usually in high yield. These imines have proved to be very versatile synthetic intermediates in heterocyclic chemistry, undergoing a variety of reactions initiated by nucleophilic attack at different sites on the dithiazole ring (the driving force being the regeneration of the latent cyano group in the dithiazole ring). Exploring the chemistry of Appel salt, we demonstrate in this paper that the starting imines 2 can be easily converted into 2-cyano derivatives of benzoxazines, benzoxazepines, quinazolines, benzothiazines, indolines, benzothiazoles and iminoquinolines. The heterocyclic compounds described are interesting precursors of biologically active molecules.
CONFORMATIONAL STUDY OF THE 1,3 N-N DISUBSTITUTED BENZOTRIAZOLIUM BROMIDE SALTS
MIRON DORU NECULAI**, SURPATEANU GHEORGHE *, NISTOR DENISA**, MARDARE IRINEL**, DRON PAUL IONUŢ**
This paper’s goal is to make a conformational study of the 1,3 N-N disubstituted benzotriazolim bromide salts. The optimised method of salt was used. Two isomeric carbanion disubstituted benzotriazolium ylides were obtained in a mixture, in the proportion 3:1. To observe those ylides, as well as the size of their rapport, the 1H-RMN spectra will be used.
COMPORTEMENT THERMIQUE DE QUELQUES SYSTEMES POLYMERE-PRINCIPES BIOACTIFS
LISA GABRIELA, HURDUC NATALIA (1), IRIMIA MARINELA, ROŞCA C., BĂLĂU LUMINIŢA, POPA MARCEL
A derivatographic investigation was performed on the thermal behavior of some polymers: chitosane, carboxymethylcellulose and systems type polymer-active principle: cloramphenicol-chitosanecarboxymethyl-cellulose. It was investigated systems in which there are covalent or ionic bold between active principle and cellulose derivates or biosyntheses polymers. The heating curves were recorded with a Paulik-Paulik-Erdei derivatograph (MOM Budapest) in static air atmospheres at heating reates 10 deg/min. Nonisothermal kinetic and thermodynamic parameters for decomposition of these systems were determined. The obtaining results revealed a multi-step degradation developing according to a complex mechanism.
CAPITALIZATION OF SPENT NiO/a-Al2O3 CATALYSTS 4. NICKEL OXIDE LEACHING MECHANISM
GAVRILĂ LUCIAN
Kinetic data concerning nickel oxide acid leaching from spent steam reforming catalysts are presented. Based on this data, a sigmoid model that describes nickel dissolution is presented. The model reveals that two steps are involved in Ni leaching: a first one with a time increasing reaction rate, corresponding to free NiO dissolution, and a second one with a time decreasing reaction rate, attributed to the dissolution of the nickel oxide entrapped in the alumina crystalline structure.
POLYESTERURETHANES UTILISEES COMME AMORTISSEURS ELASTIQUES
STELIAN VLAD
In this work it is presented a study about polyesterurethane used as an elastic damper, with a large area of application in the machine construction industry, the automotive industry, the bearings’ industry and so on. The polymers which make the objective of this study are the thermoplastic polyurethane based on polyesters with end hydroxyl group, diisocyanates, diols and glycerin. The goal of this article is to obtain the polyesterurethanes with a good resistance at repeated flexion, a huge resilience, a good resistance at crash, a good abrasion resistance and an hardness between 60 – 85 oSh A.
IMPLICATION DES THIONESTERS DANS LA CONSTRUCTION D'HETEROCYCLES SOUFRES
COUTURE AXEL, GRANDCLAUDON PIERRE*
not available
POLYANILINE AS A NEW SOLID BASE CATALYST IN MICROWAVE ASSISTED ORGANIC CHEMISTRY
GOSPODINOVA NATALIA*, FRÈRE STÉPHANE, VALÉRIE THIÉRY, BESSON THIERRY*
A new solid base catalyst in microwave assisted organic chemistry is proposed. Successful replacement of sodium hydride by environmentally friendly polyaniline based catalyst is achieved to convert iminodithiazoles into aryl isothiocyanates and quinazolines under microwaves. The simple ha nding, reusability and possibility of "dry media" microwave processes represent the main advantages of polyaniline based catalyst.
ETUDE DE LA STABILITE THERMIQUE ET DE L’ACTIVITE BIOLOGIQUE DES N,N-DIALKYL DITHIOCARBAMATES DE PHENACYLE ET DES FLAVANONES CORRESPONDANTES
FÎNARU ADRIANA (1), GROSU MIRELA (1), PRISECARU MARIA (1), SEGAL EUGEN (2)
The paper present data concerning the evaluation of thermal stability and biological activity of some N,N-dialkyl dithiocarbamates and corresponding flavanones. The biological activity tests were conducted on wheat (Triticum aestivum L) and medicinal herbs (Stachys sieboldii).
ETUDE DE LA POSSIBILITE DE DEPOLLUTION DES EAUX USEES CONTENANT NICKEL AVEC DES ARGILES. 1. INFLUENCE DE LA TEMPERATURE
NISTOR DENISA*, SIMINICEANU ILIE**, AZZOUZ ABDELKRIM*
This paper contains researches regarding the influence of temperature on the kinetic mechanism of nickel fixation by using cationic clays. The separation of nickel from dilute aqueous systems is studied for environmental protection and nickel recovery. In this paper was studied the fixation of nickel from dilute aqueous solutions by ion exc hange with crude clays in direct relation with temperature. The results, showing the direct dependence for ion exchange process with working conditions.
MOYENS D’EVALUATION DE L’IMPACT PRODUIT SUR L’ENVIRONNEMENT PAR L’ACTIVITE D’EXPLOITATION ET DE PREPARATION DU SOUFRE CALIMANI
DIŢOIU VALERIA*, CIOBANU DOMNICA**
In this paper two environmental impact assessments models for a sulfur mining and preparation activity are presented: one method use a graphical presentation of the way in which a set of criteria are fulfilled and the method use an environmental pollution index calculation. For the analyzed anthropical activity, the conclusion is that all the environmental elements were heavy affected and urgent ecological reconstruction measures are to be taken.
ETUDE COMPARATIVE DES PROCESSUS DE DEPOLLUTION EN UTILISANT DES ARGILES NATURELLES ET MODIFIEES CHIMIQUE
NISTOR DENISA*, SIMINICEANU ILIE**, AZZOUZ ABDELKRIM*
The separation of copper from dilute aqueous systems is studied for environmental protection. In this paper was studied the removal of copper from dilute aqueous solutions by ion exchange with crude clays and chemical modified clays (pillared layer clays).
GALVANIC CORROSION IN COOLING WATER ENVIRONMENTS
GAVRILĂ LUCIAN, GAVRILĂ DANIELA, SIMION ANDREI, CASARES MARTIN CAROLINA *
Severe galvanic corrosion problems have been identified mainly in heat exchangers used in several industrial cooling systems from chemical plants, refineries, power plants. The causes of heat exchangers failure and the modalities to avoid it in the future are discussed, emphasizing mainly the role of design, operation, maintenance and reparation of this type of equipment.