On the 𝔉‐hypercentre of a finite group

The main objective of this paper is to study and describe the hypercentre of a finite group associated with saturated formations, in terms of some subgroup embedding properties related to permutability. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Optical Properties of Model Moderately Coupled Plasmas

We review our approach to the modelling of optical properties of model moderately coupled plasmas. On the basis of the classical theory of moments the external and internal dynamic conductivities and the reflectivity coefficient of a model hydrogen moderately coupled plasma are determined using all known exact relations and sum rules. The sum rules which are the power frequency moments of the loss function are calculated using the Deutsch effective potential and the hypernetted chain equations. MD simulation data are used and numerical simulations are suggested (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Palladium catalyzed synthesis of a chromenes and chromenols

Palladium catalyzed coupling of tertiary allylic alcohols (having five, ten or fifteen carbon atoms) with 2-iodophenols or hydroquinones furnishes the corresponding 2,2-disubstituted chromenes (2H-1-benzopyrans) and chromen-6-ols.     

A crystalline sponge based on dispersive forces suitable for X-ray structure determination of included molecular guests

A crystalline porous material showing one-dimensional (1-D) rectangular micropores (12 × 9 Ų) has been assembled from a semirigid macrocyclic tetraimine and EtOAc as the templating agent. The 1-D nature of the material is intrinsic to the conformationally rigid structure of a macrocyclic sub-unit bearing four cyclohexylidene residues. The multiple dispersive forces established among the aliphatic residues glutted the 1-D channels and provided thermal stability to the material at temperatures below 160 °C. Upon removal of the template, the structure of the empty solid exhibited permanent microporosity (S _BET = 342 m² g^–1). Being a true molecular sponge, the channel framework of this material allowed the inclusion of a variety of molecular sample guests without compromising its crystalline nature. Remarkably, this crystalline material enabled the structure determination by X-ray diffraction of the included molecules. Theoretical studies demonstrated the vital role played by the dispersive forces in the overall stabilization of the crystal packing.     

Lithium trienolate of sorbic acid as a d6 synthon. Synthesis of 7-hydroxy 2,4-dienoic acids.

The trienolate $\text{2}$ of sorbic acid is an easily available d⁶ synthon. Preparation of 7 hydroxy dienoic acids $\text{5}$ from ketones is here described.     

Isotope dilution GC-MS routine method for the determination of butyltin compounds in water

A standard GC-MS instrument with electron impact ionisation has been used to develop a fast, simple and reliable method for the simultaneous determination of monobutyltin (MBT), dibutyltin (DBT) and tributyltin (TBT) in water samples. Isotope dilution analysis (IDA) is used for the determination of species, taking advantage of a commercially available spike solution containing a mixture of MBT, DBT and TBT enriched in ¹¹⁹Sn. Method detection limits for 100-mL samples were between 0.18 and 0.25 ng L⁻¹ for the three butyltin compounds with typical RSD between 2 and 4% at levels between 100 and 10 ng L⁻¹, respectively. Recovery of tin species in spiked samples (natural water, wastewater and seawater) was quantitative. The stability of butyltin compounds in collected seawater samples was also studied. The addition of a 1% (v/v) glacial acetic acid preserved tin species in the samples for at least 5 days at room temperature. The IDA method was finally implemented in a routine testing laboratory and it was subsequently accredited by the Spanish National Accreditation Body according to the requirements of UNE-EN ISO/IEC 17025.     

Hybrid cavitand-resorcin[4]arene receptor for the selective binding of choline and related compounds in protic media

[structure: see text] A hybrid cavitand-resorcin[4]arene receptor capable of displaying pH-modulated binding affinity toward trimethylalkylammonium ions is proposed as an alternative to the low selectivity exhibited by other receptors used in supramolecular fluorescent sensor systems for choline.     

Guest Exchange Mechanisms in Mono‐Metallic PdII/PtII‐Cages Based on a Tetra‐Pyridyl Calix[4]pyrrole Ligand

Planar pyridyl N‐oxides are encapsulated in mono‐metallic Pd^II/Pt^II‐cages based on a tetra‐pyridyl calix[4]pyrrole ligand. The exchange dynamics of the cage complexes are slow on both the NMR chemical shift and EXSY timescales, but encapsulation of the guests by the cages is fast on the human timescale. A “French doors” mechanism, involving the rotation of the meso‐phenyl walls of the cages, allows the passage of the planar guests. The encapsulation of quinuclidine N‐oxide, a sterically more demanding guest, is slower than pyridyl N‐oxides in the Pd^II‐cage, and does not take place in the Pt^II counterpart. A modification of the encapsulation mechanism for the quinuclidine N‐oxide is postulated that requires the partial dissociation of the Pd^II‐cage. The substrate binding selectivity featured by the cages is related to their different guest uptake/release mechanisms.