Synthesis of NaX and NaY Zeolites from Tunisian Kaolinite as Base Catalysts: An Investigation of Knoevenagel Condensation

The synthesis of Faujasite‐type zeolites with high purity has been successfully performed from Tunisian kaolinite and the effects of different crystallization parameters on the final products were widely investigated. The alkaline fusion of kaolinite followed by hydrothermal treatment lead to zeolite NaX synthesis whereas the classic hydrothermal transformation of metakaolinite produces NaY zeolite. The results show that an increase in the synthesis temperature and time has improved the crystallization process of the zeolite NaX whereas the SiO₂/Al₂O₃ and the Na₂O/SiO₂ molar ratios were the key parameters to obtain a pure zeolite NaY. The highest specific surface areas obtained with the optimal crystallization conditions were 554 m2 g^?1 and 592 m2 g^?1 for respectively NaX and NaY zeolites. The basic properties of NaX and NaY zeolites were explored in the Knoevenagel condensation of benzaldehyde with ethyl cyanoacetate at 140 °C as a test reaction in the absence of solvent. The influence of ion exchange with cesium cation on the catalytic activity of prepared catalysts was also investigated. It was found that the NaX provided higher activity than that of NaY catalyst due to its lower Si/Al ratio whereas a cesium exchange conferred higher basicity to the prepared Na‐faujasite.     

Phytochemical Characterization and Bioactivity of Asparagus acutifolius: A Focus on Antioxidant,Cytotoxic, Lipase Inhibitory and Antimicrobial Activities

The phytochemical composition of leaves, stems, pericarps and rhizomes ethanolic extracts of Asparagus acutifolius were characterized by HPLC-DAD-MS. A. acutifolius samples contain at least eleven simple phenolics, one flavonon, two flavonols and six steroidal saponins. The stem extracts showed the highest total phenolic acid and flavonoid contents, where cafeic acid and rutin were the main compounds. No flavonoids were detected in the leaf, pericarp or rhizome while caffeic acid and ferulic acid were the predominant. Steroidal saponins were detected in the different plant parts of A. acutifolius, and the highest contents were found in the rhizome extracts. The stem extracts exhibited the highest antioxidant activity against 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP) and the highest 2,2-azino-bis (3 ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging activity was found in the pericarp extracts. The rhizome and leaf extracts showed a potent cytotoxic activity against HCT-116 and HepG2 cell lines. Moreover, the pericarp and rhizome extracts revealed a moderate lipase inhibitory activity. The leaf and rhizome extracts were screened for their antimicrobial activity against human pathogenic isolates. The leaf extract exhibited a powerful inhibitory activity against all the bacteria and fungi tested.     

Vibrational analysis of amino acids and short peptides in hydrated media. I. L-glycine and L-leucine

Raman scattering and Fourier-transform infrared (FT-IR) attenuated transmission reflectance (ATR) spectra of two alpha-amino acids (alpha-AAs), i.e., glycine and leucine, were measured in H2O and D2O (at neutral pH and pD). This series of observed vibrational data gave us the opportunity to analyze vibrational features of both AAs in hydrated media by density functional theory (DFT) calculations at the B3LYP/6-31++G* level. Harmonic vibrational modes calculated after geometry optimization on the clusters containing each AA and 12 surrounding water molecules, which represent primary models for hydration scheme of amino acids, allowed us to assign the main observed peaks.     

Liquid|liquid electrochemical bicarbonate and carbonate capture facilitated by boronic acids

Reversible bicarbonate and carbonate liquid|liquid ion transfer processes from aqueous solution into an organic 4-(3-phenylpropyl)pyridine phase are driven electrochemically with TPPMn(III/II) and shown to be facilitated over a wide pH range by 2-naphthylboronic acid (bicarbonate transfer potential -0.08 V vs. SCE; binding constant K(AB) = 10(2) mol(-1) dm(3) and carbonate dianion transfer potential 0.07 V vs. SCE; binding constant K(AB2) = 2 × 10(10) mol(-2) dm(6)).     

Existence Results for Critical Semi-linear Equations on Heisenberg Group Domains

Following the work of G. Citti and F. Uguzzoni who studied Yamabe type problems on Heisenberg group domains, we consider here the following critical semi-linear equation on domains of the Heisenberg group ${{\mathbb{H}^1}}$ : $$(P) \left\{\begin{array}{lll}-{\Delta_{H}}u\quad =\quad K{u^{3}}\quad\,{\rm in}\,\,\Omega,\\ \quad\quad\,{u}\quad > \quad0\qquad\,\,\,\,{\rm in}\,\,\Omega,\\ \quad\quad\,{u}\quad = \quad 0 \quad\quad\,\,\,{\rm on}\,\partial \Omega, \end{array}\right. $$ where Δ _H is the sublaplacian on ${{\mathbb{H}^1}}$ and K is a C ³ positive function defined on Ω. Using a version of the Morse Lemma at infinity, we give necessary conditions on K to insure the existence of solutions for (P).     

Étude de l’activité catalytique des argiles pontées aluminium,zirconium et cérium dans la synthèse du 2,2-diméthyl-1,3-dioxolane

The purified Tunisian clay G and the commercialized American clay W were pillared with zirconium, aluminum and mixed pillars zirconium–aluminum, cerium–zirconium, cerium–aluminum, and cerium–zirconium–aluminum. These different clays were used in the synthesis of 2,2-dimethyl-1,3-dioxolane 3 by acetalyzation of acetone 2 with ethylene glycol 1 under autogenously pressure and without solvent. Results indicate that the yield of product 3 depends of the nature and the acidity of the clay used and the time of reaction.     

Synthesis and X-ray structure of cationic methallyl palladium complexes supported by unsymmetrical β-diimine ligands

Treatment of the unsymmetrical β-iminoamine ligands [PhCN(Ar)CHCNH(Ar)Me] with the zerovalent complex Pd(dba)₂ in the presence of the methallyloxyphosphonium salt, gives high yields of the cationic β-diimine complexes [PhCN(Ar)CH₂CN(Ar)(Me)Pd(η³-C₄H₇)]⁺[PF₆]⁻ (Ar = 2-Me-C₆H₄ (7); 2-MeO-C₆H₄ (8); 2,6-Me₂-C₆H₃ (9); 2,6-iPr₂-C₆H₃ (10)). All the new complexes have been characterised by NMR and IR spectroscopy. The structure of the cationic methallyl palladium complex (10) has been solved by X-ray crystallography.     

Boronic acid-facilitated α-hydroxy-carboxylate anion transfer at liquid/liquid electrode systems: the EICrev mechanism

The transfer of the α-hydroxy-carboxylates of glycolic, lactic, mandelic and gluconic acid from the aqueous electrolyte phase into an organic 4-(3-phenylpropyl)-pyridine (PPP) phase is studied at a triple-phase boundary electrode system. The tetraphenylporphyrinato complex MnTPP dissolved in PPP is employed to drive the anion transfer reaction and naphthalene-2-boronic acid (NBA) is employed as a facilitator. In the absence of a facilitator, the ability of α-hydroxy-carboxylates to transfer into the organic phase improves, consistent with hydrophobicity considerations giving relative transfer potentials (for aqueous 0.1 M solution) of gluconate>glycolate>lactate>mandelate. In the presence of NBA, a shift of the reversible transfer potential to more negative values is indicating fast reversible binding (the mechanism for the electrode process is EIC_rev) and the binding constants are determined as K _glycolate = 2 M⁻¹, K _mandelate = 60 M⁻¹, K _lactate = 130 M⁻¹ and K _gluconate = 2,000 M⁻¹. The surprisingly strong interaction for gluconate is rationalised based on secondary interactions between the gluconate anion and NBA.