Metal Oxide Assisted Preparation of Core–Shell Beads with Dense Metal–Organic Framework Coatings for the Enhanced Extraction of Organic Pollutants

Dense and homogeneous metal–organic framework (MOF) coatings on functional bead surfaces are easily prepared by using intermediate sacrificial metal oxide coatings containing the metal precursor of the MOF. Polystyrene (PS) beads are coated with a ZnO layer to give ZnO@PS core–shell beads. The ZnO@PS beads are reactive in the presence of 2‐methylimidazole to transform part of the ZnO coating into a porous zeolitic imidazolate framework‐8 (ZIF‐8) external shell positioned above the internal ZnO precursor shell. The obtained ZIF‐8@ZnO@PS beads can be easily packed in column format for flow‐through applications, such as the solid‐phase extraction of trace priority‐listed environmental pollutants. The prepared material shows an excellent permeance to flow when packed as a column to give high enrichment factors, facile regeneration, and excellent reusability for the extraction of the pollutant bisphenol A. It also shows an outstanding performance for the simultaneous enrichment of mixtures of endocrine disrupting chemicals (bisphenol A, 4‐tert‐octylphenol and 4‐n‐nonylphenol), facilitating their analysis when present at very low levels (<1 μg L^?1) in drinking waters. For the extraction of the pollutant bisphenol A, the prepared ZIF‐8@ZnO@PS beads also show a superior extraction and preconcentration capacity to that of the PS beads used as precursors and the composite materials obtained by the direct growth of ZIF‐8 on the surface of the PS beads in the absence of metal oxide intermediate coatings.     

Microwave-assisted synthesis of 4-quinolylhydrazines followed by nickel boride reduction: a convenient approach to 4-aminoquinolines and derivatives

Nickel(II) chloride/sodium borohydride combination was employed for the reduction of 4-hydrazinoquinoline derivatives to the corresponding anilines. This reductive protocol was efficiently applied for the reductive cleavage of monosubstituted hydrazines. We described herein the microwave-assisted synthesis of 4-hydrazinoquinolines, which furnished a high yielding and rapid two-step procedure for the synthesis, under mild conditions, of 4-aminoquinolines as antimalarial precursors.     

Molecular structure refinement of a segmented thermotropic polyester containing an aromatic triad mesogen

The polymorphic behavior of a polyester consisting of an aromatic triad mesogen and a flexible spacer has been investigated. The effect of thermal and mechanical treatment on the appearance of two crystalline phases stable at room temperature is discussed. The molecular packing (triclinic cell, space group P1 ) and the morphological parameters of the crystalline phase stabilized by drawing process are evaluated and refined. The whole-pattern method, based on the analysis of the whole x-ray diffraction pattern from fiber samples of polymer, has been employed. The molecular packing resembles very much that of polyethylene terephthalate. ©1995 John Wiley & Sons, Inc.     

Soluble (HN)2-groups

In this paper we investigate the class of finite soluble groups in which every subnormal subgroup has normal normalizer. In particular we prove that they areUN ₂U, whereU andN ₂denote finite abelian groups and of finite nilpotent groups of class at most 2 respectively.     

Synthesis and use of stereospecifically deuterated analogues of palmitic Acid to investigate the stereochemical course of the delta11 desaturase of the processionary moth

Thaumetopoea pityocampa pheromone glands contain desaturases that, after several sequential reactions from palmitic acid, catalyze the formation of a unique enyne fatty acid, which is the immediate sex pheromone precursor. In this article, we describe the synthesis of different stereospecifically deuterium-labeled and isotopically tagged palmitic acid probes needed to decipher the stereochemical course of the T. pityocampa Delta(11) desaturase. The synthesis of probes has been carried out by a chemoenzymatic route, in which the key step is the kinetic lipase-catalyzed resolution of racemic mixtures of secondary propargyl alcohols. The presence of the acetylenic bond simplifies the absolute configuration determination of the resolved alcohols. Moreover, it allows the introduction of the isotopic tag by deuteration. By use of the probes thus prepared, experimental evidence is presented that the Delta(11) desaturase of T. pityocampa transforms palmitic acid into (Z)-11-hexadecenoic acid by removal of the pro-(R)-hydrogen atoms from both C11 and C12.     

A new quality control material for marine environmental analysis

The implementation of the European Water Framework Directive (WFD) and of the sediment-quality criteria related to the potential disposal of dredged materials is expected to involve a substantial increase in the number of chemical analyses performed in marine environmental control laboratories. The chemical characterization of sediments (metals, elemental composition, etc.) and the potential release of metals under changing environmental conditions are relevant when dealing with risk assessment. The present paper describes the preparation of a quality control material (QCM) harbor sediment carried out in a specifically equipped laboratory at the University of Barcelona. The results of homogeneity and stability studies for total metal content (Cd, Cr, Cu, Ni, Pb, and Zn), extractable metal following the BCR three-step sequential extraction procedure (BCR-SEP), and total carbon content show the suitability of QCM for multi-parameter routine quality control (QC) in marine environmental laboratories.     

Asymmetric hydroformylation of styrene catalyzed by furanoside phosphine–phosphite–Rh(I) complexes

A series of phosphine–phosphite ligands, derived from inexpensive -(+)-xylose, were tested in the Rh-catalyzed asymmetric hydroformylation of styrene. Systematic variation of the phosphite moiety revealed a remarkable effect on the selectivity of the hydroformylation catalysts. High regioselectivities for 2-phenylpropanal (up to 95%) and moderate enantioselectivity were found under mild reaction conditions (25–40°C, 25 bar of syn gas). The hydroformylation results are explained by the solution structures of the intermediate species formed under hydroformylation conditions.     

Comparison between triplet and singlet molecular oxygen oxidation of fully substituted alkoxyoxazoles

Oxidation by ground-state molecular oxygen of fully substituted alkoxyoxazoles I gave imines IV as major products; diacylcarbamates III were also obtained as minor products. The free radical nature of the autoxidation was established. A mechanistic interpretation of the results is suggested also in the light of the results of the oxidation with singlet oxygen.