In this study, density functional theory (DFT) calculations have been performed to investigate the adsorption mechanisms of toluene and water onto various cationic forms of Y zeolite (LiY, NaY, KY, CsY, CuY and AgY). Our computational investigation revealed that toluene is mainly adsorbed via π–interactions on alkalis exchanged Y zeolites, where the adsorbed toluene moiety interacts with a single cation for all cases with the exception of CsY, where two cations can simultaneously contribute to the adsorption of the toluene, hence leading to the highest interaction observed among the series. Furthermore, we find that the interaction energies of toluene increase while moving down in the alkaline series where interaction energies are 87.8, 105.5, 97.8, and 114.4 kJ/mol for LiY, NaY, KY and CsY, respectively. For zeolites based on transition metals (CuY and AgY), our calculations reveal a different adsorption mode where only one cation interacts with toluene through two carbon atoms of the aromatic ring with interaction energies of 147.0 and 131.5 kJ/mol for CuY and AgY, respectively. More importantly, we show that water presents no inhibitory effect on the adsorption of toluene, where interaction energies of this latter were 10 kJ/mol (LiY) to 47 kJ/mol (CsY) higher than those of water. Our results point out that LiY would be less efficient for the toluene/water separation while CuY, AgY and CsY would be the ideal candidates for this application.
Low level of polyphenols absorption is due among other things to the formation of irreversible complexes between non-heminic iron (Fe 2+ , Fe 3+) and these polyphenols through their hydroxyl groups. Understanding of these complexes formation mechanisms led us to explore hydroxyl groups acidity of these polyphenols monomers (catechin, epicatechin, gallocatechin and epigallocatechin) mainly found in food. Quantum chemistry modelling, more precisely the functional density theory (DFT) method, associated to 6-311G (d, p) base was used in gas phase. Spectroscopic, thermodynamic descriptors and geometric parameters resulting from calculations showed a slight stability of catechin compared to epicatechin and gallocatechin compared to epigallocatechin. As for the acidity of these monomers hydroxyl groups, the results show that it decreases similarly as follows: O
Benzothiazoles are organic compounds with multiple biological activities. Due to their biological interests, these are synthesized on a large scale at the industrial level and used in various fields. Their release into waters causes environmental problems which leads to public health problems. Finding solution which can help for their degradation become necessary.
That is the reason why a theoretical study of the reactivity of five benzothiazole derivatives has been initiated in order to understand some aspect of their biodegradation.
The calculations were carried out in gaseous and aqueous phase with B3LYP functional associated with bases 6-311G(d) and 6-31+G(d).
The results revealed that the thione tautomer of the MBT derivative is more stable than the thiol form. These results are in agreement with previous experimental work which showed that the thiones forms in MBT metal complexes are the most stable. Moreover, the study of the reactivity based on the computation of the global indices of reactivity reveals that the benzothiazoles BT, OBT and MBT are the most reactive. The most electrophilic is BT and the least electrophilic is MTBT. In addition, the thermodynamic parameters and the energy barriers predict a possibility of coexistence of tautomers ol and one of OBT derivative. Fukui dual descriptors have shown that the carbon C2 of BT is the most electrophilic. In substituted derivatives, it is the C6 carbon that is the most electrophilic. N3 nitrogen remains the most nucleophilic site in all the studied molecules.
L'étude théorique de la synthèse de la calothrixine et de ses analogues a été réalisée. Cette synthèse procède par une réaction hétéro-Diels-Alder de type [4+2] entre un azadiène et des diénophiles substitués. Cette réaction est régiosélective et les diénophiles éléctro-donneurs favorisent la formation de l'isomère majoritaire. Les résultats théoriques sont en accord avec les résultats expérimentaux.
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