321 research outputs found
Disappearing conglomerates, assessment of the threat
International audienc
On the existence of a dynamic critical point by using wet milling on (±) modafinil
This study has been carried out on the molecular compound (±)
modafinil, which exhibits five pure polymorphic forms (I, III, IV,
V and VI). At P = 1 atm, irrespective of temperature and without
any milling energy, Form I is the stable form. Therefore, the other
polymorphic forms (III, IV, V and VI) are of monotropic
character.
The steady states of (±) modafinil have been investigated as a function of wet milling parameters (milling intensity and water concentration). The results presented here suggest the existence of a dynamic critical point defined by Tc â 40°C, Pc â 1 atm, Ic â k R; R=50, Xc = 2% mass percent of water, respectively the critical: mean temperature, global pressure, milling intensity proportional to R and water composition (in mass percent)
In situ X-ray for monitoring crystallization in solution : In-situXÂź
International audienc
Relevance of Second Harmonic Generation Microscopy (SHG-M) in Material Sciences
International audienc
Practical Role of Racemization Rates in Deracemization Kinetics and Process Productivities
International audienc
Prenucleation self-assembly and chiral discrimination mechanisms during solution crystallisation of racemic diprophylline
The crystallisation behaviour of (RS)-diprophylline (DPL) in two different solvents is investigated to assess the incidence of solvated pre-associations on nucleation, crystal growth and chiral discrimination. In the solvated state, Raman spectroscopy shows that dimeric associations similar to those depicted in the crystalline solid solution (ssRII) predominate in isopropanol (IPA), which may account for the systematic spontaneous nucleation of this crystal form from this solvent. By contrast, spontaneous nucleation in DMF yields the stable racemic compound RI, consistently with the distinct features of the Raman spectrum collected in this solvent. A crystal growth study of ssRII in IPA reveals that the crystal habitus is impacted by the solution enantiomeric excess; this is explained by increased competition between homo- and heterochiral pre-associations. This is supported by a molecular modelling study on the enantiomeric selectivity of the DPL crystal lattices. The combination of assessment methods on solution chemistry, nucleation and chiral discrimination provides methodological tools from which the occurrence of solid solutions can be rationalised
Chirality and supramolecular chirality, chiral discrimination in the solid-state and break of symmetry
International audienc
Chiral Discrimination in the Solid State: Applications to Resolution and Deracemization
International audienc
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