N-(2-cyanophenyl) imidates 1a and 2-cyanocrotonoimidates 1b react with hydrazines to produce respectively 3-amino-4-iminoquinazolines 3a and 3-amino-4-iminopyrimidines 3b. Treatment of these products with orthoesters yields (1,2,4)triazolo(1,5,c) quinazolines 6a and (1,2,4)triazolo(1,5,c)pyrimidines 6b. The types of product obtained gave information relevant to the elucidation of the mechanism of cyclisation.
M.L. Benkhoud, H. Mraïhi, B. Baccar
Pages 145-151
The fragmentation reactions of α-fluoroepoxides (1-4), aliphatic epoxides (1' and 4'), β-fluoro glycidyl ethers (5-8) and α-F-alkylated vinylic glycidyl ethers (9-11) in the 70 eV mass spectra have been studied. The fluorinated fragments are the principal peaks in the spectra of the secondary α-fluoroepoxides. In the case of the β-fluoro or α-F-alkylated glycidyl ethers, the α-cleavage at the ether function is the preferred fragmentation pathway.
I. Chehidi, M.M. Abdelkafi, M.M. Chaabouni, A. Baklouti
Pages 153-162
Cathodic cleavage of some tosylamides of particular interest, by electron carriers between the cathode and the solution is reported. Using a proper choice of some sulfonamides, it is shown that the chemical reaction subsequent to the electron transfer can be the rate determining step. On the other hand we have established that the catalytic peak current was divided into two peaks when the catalytic effect was strong. Standard potential is also determined for some of these compounds.
L. Chirchi, K. Boujlel
Pages 163-170
The formation constants of Ag+ complexes with some nitrogen heterocycles compounds have been determined by potentiometric measurements at 25°C in acetonitrile solvent, where the silver(I) is stable. These constants values have been determined by three methods : one graphical method that can determine approximately these values and the superior order of these complexes and two methods of statistic calculation using two programs : TOT and MINIQUAD. These last methods give a better precision.
H. Maghraoui, M. dachraoui
Pages 171-181
Water vapor adsorption on activated alumina has been determined by a flow method for three temperatures ranging from 22.5°C to 60°C. Dissociative chemisorption occurs on dehydroxylated surface of alumina followed by strong molecular adsorption, multilayer edification and capillary condensation. The determination of the quantity of water vapor adsorbed indicates that a molecule of water is physically linked on two adjacent hydroxyl groups. In the first molecular layer, the high initial heat of adsorption is attributed to the formation of a hydrogen-bond and the polarity of the adsorbent. In the multilayers and the capillary condensation ranges, the heat of adsorption is constant and equal to the condensation heat. Three models are used to fit the adsorption isotherms data. In particular, BET equation with finite molecular layers provides a number of molecular layers n similar to that calculated from the mean pore size of the adsorbent and the thickness of the adsorbed film.
M. Baguenne, A. Bellagi
Pages 183-193
The preparation of coal aqueous suspension was followed by simple physical methods. It requires the use of surfactants, additives (salt or base) or additions such as lignosulphonates and phosphates. The prepared suspensions in presence of the surfactant, Surfaron S 1520 N, proved to be the least stable; the presence of salt, and mainly ammonia, has a positive effect on fluidity and stability. The emulsions obtained in the simultaneous presence of lignosulphonate (Vanisperse) and of phosphate (TPPNa) conducted in a concentrated medium (70% of coal mass) has stable products. The determinant factor in that case is the ratio: TPPNa concentration / Vanisperse concentration.
T. Hamiah, A. Bouassida
Pages 195-202
This paper presents the exergy analysis of an industrial plant for the production of sulfuric acid. We give a brief description of the process and the general procedure for the calculation of the irreversibilities. We develop a computer program to solve and calculate all the exergy and mass balances. The validation of this model is done by the utilization of the data of the industrial plant. The results obtained allow us to identify the parts were the energy is mainly degraded and can be used as a guide for future improvements in the plant.
M.R. Jeday, K. Chekir.
Pages 203-215