The structural data of two varieties of the title compound as well as the corresponding irreversible polymorphic transition are detailed. Although extensive structural analogies are pointed out, the transition is of destructive/reconstructive type with a poor rate requiring days or even weeks for completion. Without seeding, evidence of epitaxial nucleation is given. The genuine impact of polymorphism on the preferential crystallization is highlighted. The greater the departure from thermodynamic equilibrium the greater the differences between the courses of the entrainments initiated with a given polymorph. The best result in terms of robustness, yield, and conditions for up-scaling is obtained by using a combination of (i) a smooth crystallization process (auto-seeded and polythermic: AS3PC), (ii) the use of the stable polymorph, (iii) a pretreatment of the solid particles designed to enlarge the surface of the solid phase ready for the crystal growth as soon as the cooling program is launched.

Polymorphic forms I and III of (() modafinil have been studied. In contrast to the structure of form I which could be solved by using conventional single crystal X-ray diffraction, the crystal structure of form III could not be elucidated due to the shape and the size of the single crystals resulting from the high supersaturation under which this phase is obtained. To bypass the problem, the derived crystal packing (DCP) model has been successfully applied by recombining the slice (002)A extracted from form I. The calculated XRPD pattern of form III fits well with the experimental data. The extensive similarities between the two crystal structures are carefully detailed. † Crystallographic data are deposited at the CCDC under number 229171.

Resolution of the title compound is carried out at a two liter scale via two different processes of preferential crystallization (PC), the Auto Seeded Programmed Polythermic Preferential Crystallization (AS3PC) process and the classical Seeded Isothermal Preferential Crystallization (SIPC) process. The ratio, crystal growth rate/secondary nucleation rate, is strongly under the influence of the process. Consequently AS3PC process appears more efficient than SIPC process in terms of purity of the crops (optical purity), yield, easiness of scale up and downstream operations such as filterability.

The effect of mechanical milling on powder mixtures consisting of graphite and AB5 alloys, prepared either by mechanical alloying or by a high‐temperature melting process, has been investigated. The resulting hydride‐forming composite electrodes show a 10 and 40% capacity enhancement for arc‐melted and mechanically prepared AB5 alloys, respectively. Such an increase in capacity is suggested to be the result of several cumulative effects: (1) a mechanically induced reducing role of graphite which eliminates the AB5 particles of oxide coatings, enabling a better hydrogen adsorption/absorption and diffusion into the insertion sites of the alloy, (2) the appearance of an increasingly important double‐layer capacitance on each particle with increased milling time that adds to the faradic component, and (3) the improved electronic conductivity between the active AB5 material and the graphite that allows a better utilization of the alloy. © 1999 The Electrochemical Society. All rights reserved.