Simultaneous microbatch screening of enantiorecognition on solid chiral selectors using selected mixtures of test-racemates: a case study on cellulose tris(alpha-phenylpropionate) with configurational diversity

An improved methodology for microbatch screening in the liquid-solid enantioselective adsorption of racemates by solid chiral selector is presented and illustrated by the evaluation of a series of six cellulose tris(alpha-phenylpropionate) presenting a configurational diversity and cellulose tris (4-methylbenzoate). Analyses were performed on 5 mg scale of chiral selector and 150 microL of supernatant containing a mixture of three test-racemates. Fifteen test-racemates were chosen according to their molecular diversity using a hierarchical clustering approach for seven selected three-dimensional molecular properties. The 15 racemates were sorted in five test mixtures composed of three racemates each according to the following constraints: each triplet of test-racemates can be analyzed without peak overlap on a commercially available chiral stationary phase (CSP). The designed five groups of three racemates may be used for the evaluation of other chiral selectors in view of the preparation of CSPs. This methodology improves the throughput of the evaluation and could be automated.     

Exact solution (within a double-zeta basis set) of the schrodinger electronic equation for water

Using recently developed theoretical techniques it has been possible to achieve an exact variational solution of the Schrödinger equation within a modest basis set or one-eleltron functions. The full configuration interaction for this system included a total of 256473 ¹A₁ spin-and space-adapted configurations. Comparison with many-body perturbation theory proves to be quite interesting.     

Chiral environments for asymmetric hydrogenation of model didehydro-amino acid residues

Dedicated to Professor John C. Sheehan on the occasion of his sixty-fifth birthday Nmr and glc analysis of diastereoisomeric mixtures of dipeptides has been used to study the asymmetric hydrogenation of model benzoyldidehydro- and trifluoroacetyldidehydro-dipeptide methyl esters. Chiral enhancement of one isomeric form appears to be independent of the N-terminal acyl group, but is significantly influenced by the choice of amino-acid in the C-terminal position. C-Terminal aromatic amino-acids and their derivatives give the best chiral enhancement during hydrogenation of a neighbouring dehydroamino-acid residue.     

Simultaneous determination of copper,mercury and antimony in biological samples by neutron activation and substoichiometric extraction

A simple and accurate method has been developed for the determination of copper, mercury and antimony by thermal neutron activation analysis involving substoichiometric extraction technique. The results of analysis indicate that copper, mercury and antimony in biological samples can be determined with an accuracy of 5.3%, 5.5% and 6.2%, respectively. Two samples and a standard can be analysed by the proposed method in about 4 hrs. Part of this work was presented at the International Conference on Modern Trends in Activation Analysis, Saclay, Paris, France, October 2–6, 1972.     

Computer programme for calculation of electric dipole moments from measurements in solution

An ALGOL computer programme is described for the calculation of an electric dipole moment from measurements made on dilute solutions in a non-polar solvent.     

Réactions des céténes et du dicéténe avec les germyl- et silylphosphines

Ketenes add to germyl- and silylphosphines R₃MPEt₂ with opening of the carbonyl group and formation of phosphorylated alkenoxygermanes or -silanes

(R′H, Ph). These adducts are thermally stable and only the addition derivative of diphenylketene and Me₃SiPEt₂ exhibits metallotropic isomerization to a C-derivative after prolonged heating. Hydrolysis of these addition compounds is a new approach to the acylphosphines R₂CH-CO-PEt₂. Diketene also reacts with germyl- and silylphosphines with acyloxygen bond cleavage and formation of metallated and phosphorylated ketoenolates of the type

. These derivatives isomerize either partially (MSi) or completely (MGe) into R₃MOC(CH₃)CHCOPEt₂. Their hydrolysis constitutes a new method of synthesis of the phosphorylated β-diketone

. The ketoenolates from the addition reaction of the hydrosilylphosphine, Me₂Si(H)PEt₂, cyclize readily after partial isomerization by the intramolecular addition SiH to CO, to give phosphorylated siladioxane and siladioxene. The conformation of these heterocyclic compounds has been studied.     

Über Alkalihexafluorobismutate(V)

The compounds LiBiF₆ (a = 5.18, c = 13.9₉ Å), NaBiF₆ (a = 5.47, c = 15.1₆ Å), RbBiF₆ (a = 7.71, c = 7.89 Å) and CsBiF₆ (a = 7.93, c = 8.27 Å, hexagonal lattice constants) are rhombohedral. The hexagonal unit cell contains three formula weights. LiBiF₆ and NaBiF₆ are isotypic with LiSbF₆, RbBiF₆ and CsBiF₆ are KOsF₆-isotypes. All compounds are colourless and very moisture sensitive.     

Construction of functional porphyrin polystyrene nano-architectures by ATRP

A series of mono-functionalized metallo-porphyrin polystyrenes have been synthesized using atom transfer radical polymerization and their self-assembling behavior was studied by electron microscopy showing that the polystyrene tail-length influences the aggregate architecture.     

Cluster aggregation: a new method for producing atomic and molecular clusters

A new method for the production of cold free clusters is presented. A beam of large rare gas clusters is passed through a low pressure atomic gas. The gas atoms are picked up by the rare gas clusters whereby they condense. A complete evaporation of rare gas atoms from the newly formed clusters then follows once the number of captured particles becomes sufficiently large. The method is demonstrated for Xe clusters with size up to 500 atoms per cluster but it should work for most materials, including the refractory materials.