Electronically ‘atypical’ a 15-type compounds based on chromium and molybdenum

The superconducting transition temperature has been investigated as a function of composition and degree of long-range order in a number of binary and ternary A 15-type phases on Cr and Mo. It is concluded that these compounds are unlike the typical Nb- or V- based phases with the same structure. The maximum T_c does usually not occur at the ideal composition. Nevertheless, a correlation has been found between T_c and the degree of order.     

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