A theoretical study of the difference in the behavior ofl- andd-alanine toward the two inverse forms of kaolinite

The adsorption ofl- andd-alanine on kaolinite is studied by means of the self-consistent field method, the field created by the crystal being simulated by that of 230 point charges, corresponding to two layers. The absolute structure we have adopted for kaolinite is that for whichthe ( ) trihedron is direct. Indeed, it has been shown that, owing to the nuclear weak interactions, this structure is more stable than the inverse structure. On the adopted structure, the l forms of the positive ion and of the zwitterion are more easily adsorbed than the d forms. The difference between the adsorption energies of thel andd forms are 0.14 and 0.04 kJ mol^–1 for the positive ion and the zwitterion, respectively. These differences are considerably larger than those arising from the weak interactions (ca. 10^–17 kJ mol^–1) so that the asymmetrical adsorption on kaolinite seems to be one of the causes of thel homochirality observed for the amino acids of proteins.     

Isomeric structures of the carbenoid,CHF2Li

The carbenoid, CHF₂Li, is suggested by $\text{ab}$$\text{initio}$ molecular orbital theory to exist in three isomeric forms, none of which corresponds to a classical tetrahedral carbon structure.     

Prostaglandin analogs modified at the 10 and 11 positions

A simplified methodology for the building of prostaglandins substituted at the 10 and 11 positions is presented.     

Nitroxydes 91 : β-Cétoénolates nitroxydes

β-Ketoaldehyde derivatives of simple piperidine and pyrrolidine nitroxides as spin labelled ligands give paramagnetic three-electron copper complexes.     

Sur un Théorème de M. A. Zorn

Sans résumé     

A diversity-oriented strategy for the construction of tetrasubstituted pyrroles via coupled domino processes

A new microwave-assisted rearrangement of 1,3-oxazolidines scaffolds is the basis for a new, metal-free, direct, and modular construction of tetrasubstituted pyrroles from terminal-conjugated alkynes, aldehydes, and primary amines. This new reaction manifold entails two linked domino processes in a one-pot manner with both atom- and bond-efficiency and under very simple and environment-friendly experimental conditions.     

Ondes et radiations électromagnétiques et gravitationelles en relativité générale

Résumé Théorie des ondes et radiations gravitationelles basée sur l’analogie existant entre les comportements du tenseur de courbure et du tenseur champ électromagnétique en relativité générale. Contribution à la quantification des champs. à Antonio Signorini pour son 70^me anniversaire.     

The Reactivity Of singlet carbenes. An ab initio study

The energy barriers for the addition to ethylene of a series of carbenes have been calculated at an ab initio level. using the STO-3G and 3-21G basis sets. It is shown that the usual extrapolation of experiment results, which predicts that the reactivity of carbenes decreases when increasing its nucleophilic character, is not valid.