Natural clay being locally abundant and cheap material in Algeria can be easily activated to become a promising adsorbent for phenol removal from aqueous solution. The natural clay before and after activation was characterized using XRD and IR techniques. The effects of various experimental parameters, such as initial phenol concentration, temperature, pH, contact time, and adsorbent dose on the adsorption extent were investigated. Langmuir adsorption model was used for the mathematical description of the adsorption equilibrium and the equilibrium data fixed very well with this model. The activated natural clay had the monolayer adsorption capacity equal to 15 mg/g at pH value of 5.0 and 23°C; adsorption measurements show that the process is very fast and physical in nature. The extent of the phenol removal increased with decrease in the initial concentration of the phenol and contact time of solution. The results showed that as the amount of the adsorbent was increased, the percentage of phenol removal increased accordingly. Thermodynamic parameters showed that the adsorption of phenol on activated natural clay was exothermic.

A series of original atropisomeric iminothiazolines 1 in which X ) OH or (and) Y ) OH were prepared from the corresponding methoxy precursors. The resolution of the atropisomeric enantiomers on chiral support is reported, and the barriers to enantiomerization are given. These barriers were determined either by off-line racemization studies or by treatment of the plateau-shape chromatogram during chromatography on chiral support. When X ) OH, the barriers are quite low due to the development of a hydrogen bond between the proton of the OH group and the nitrogen of the imino group. For these compounds, plateau shape chromatograms were obtained during HPLC on chiral support. DFT calculations confirmed the occurrence of hydrogen bonding all along the rotation process and produced calculated barriers in close agreement with the experimental data. Compound 1i (OH, OH) in which both X and Y are hydroxy groups was particularly easy to prepare by demethylation with BBr 3 of the dimethoxy precursor. Since the above-mentioned precursor is readily available from N,N′-bis(2-methoxyphenyl)thiourea and 1-chloropropan-2-one, 1i (OH, OH) is a good candidate for further functionalization. Atropisomerism in a 12-membered bridged bisether prepared from 1i (OH, OH) is reported as an illustrating example.

Semi-preparative resolution of the atropisomers by chiral liquid chromatography and determination of the barriers to rotation has allowed an unequivocal identification of the regioisomers produced by the reaction between N-(2-methoxyphenyl)-N'-(2-methylphenyl)thiourea and α-chloroacetone. Attention is drawn on the potential use of these optically pure atropisomers as new non-biaryl ligands for enantioselective metal catalysis.

Our results suggest that exposure to phthalates during gestational and lactational phases negatively impacts the development of the small intestine.

No abstract

Lipidomics calls for information on detected lipids and conjugates whose structural elucidation by mass spectrometry requires to rationalization of their gas phase dissociations toward collision-induced dissociation (CID) processes. This study focused on activated dissociations of two lipoamino acid (LAA) systems composed of N-palmitoyl acyl coupled with aspartic and glutamic acid mono ethyl esters (as LAA and LAA). Although in MS/MS, their CID spectra show similar trends, e.g., release of water and ethanol, the [(LAA+H)-CHOH] product ions dissociate via distinct pathways in sequential MS experiments. The formation of all the product ions is rationalized by charge-promoted cleavages often involving stepwise processes with ion isomerization into ion-dipole prior to dissociation. The latter explains the maleic anhydride or ketene neutral losses from N-palmitoyl acyl aspartate and glutamate anhydride fragment ions, respectively. Consequently, protonated palmitoyl acid amide is generated from LAA whereas LAA leads to the [*E+H-HO] anhydride. The former releases ammonia to provide acylium, which gives the C H and C H carbenium series. This should offer structural information, e.g., to locate either unsaturation(s) or alkyl group branching present on the various fatty acyl moieties of lipo-aspartic acid in further studies based on MS experiments.

In this work we report the preparation of ZSM-5 (pyrr) with molar composition: 0.2057Na 2 O -0.00266Al 2 O 3 -SiO 2 -0.68Pyrr (pyrrolidine) -40 H 2 O -0.12H 2 SO 4 by hydrothermal synthesis method. The sample is characterized using IR spectra, MEB and XRD. The removal of Methyl Green (MG) dye from aqueous solutions onto ZSM-5(pyrr.), is examined under various experimental conditions (dyes concentration, amount H-ZSM-5(pyrr.), temperature, pH and contact times).The adsorbed amount increased with increasing amount dye, amount H-ZSM-5(pyrr.), time, temperature and PH. The linear correlations of Langmuir and Freundlich isotherms are determined. The experimental results show that we have model Langmuir. Free energy "G° enthalpy "H°, entropy "S° and activation energy E a are determined. The "H°, "G° and E a values indicated that the adsorption of methyl green dye onto H-ZSM-5(pyrr.) is exothermic physisorption process. Kinetics analyses are conducted using pseudo first-order, second-order and the intraparticle diffusion models. The results showed that the adsorption kinetics was controlled by a pseudo second-order model.

No abstract