- Supramolecular metathesis: Co-former exchange in co-crystals of pyrazine with (R,R)-, (S,S)-, (R,S)- and (S,S/R,R)-tartaric acid
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Co-crystals of dextro-(R,R), levo-(S,S), meso-(R,S) and racemic (R,R-S,S)-tartaric acid with pyrazine were obtained by manual kneading and slurry experiments; subsequent reactions in the solid state between these co-crystals and the various forms of tartaric acid in the solid state and via slurry show that co-former exchange takes place according to the sequence of stability [(R,S)-ta]2·py > (S,S/R,R)-ta·py > (R,R)-ta·py or (S,S)-ta·py.
- Braga, Dario,Grepioni, Fabrizia,Lampronti, Giulio I.
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- Decorated single-enantiomer phosphoramide-based silica/magnetic nanocomposites for direct enantioseparation
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The nano-composites Fe3O4SiO2(-O3Si[(CH2)3NH])P(O)(NH-R(+)CH(CH3)(C6H5))2 (Fe3O4SiO2PTA(+)) and Fe3O4SiO2(-O3Si[(CH2)3NH])P(O)(NH-S(-)CH(CH3)(C6H5))2 (Fe3O4SiO2PTA(-)) were prepared and used for the chiral separation of five racemic mixtures (PTA = phosphoric triamide). The separation results show chiral recognition ability of these materials with respect to racemates belonging to different families of compounds (amine, acid, and amino-acid), which show their feasibility to be potential adsorbents in chiral separation. The nano-composites were characterized by FTIR, TEM, SEM, EDX, XRD, and VSM. The VSM curves of nano-composites indicate their superparamagnetic property, which is stable after their use in the separation process. Fe3O4, Fe3O4SiO2, Fe3O4SiO2PTA(+) and Fe3O4SiO2PTA(-) are regularly spherical with uniform shape and the average sizes of 17-20, 18-23, 36-47 and 43-52 nm, respectively.
- Karimi Ahmadabad, Fatemeh,Pourayoubi, Mehrdad,Bakhshi, Hadi
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- Plaster retarding composition
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The present invention is related to a calcium tartrate plaster retarding composition, characterised in that it has a mean particle size lower than 30 μm,The present invention is also related to the plaster comprising said composition and to the preparation process of said composition.
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- 4-AcNH-Tempo-catalyzed oxidation of aldoses to aldaric acids using chlorine or bromine as terminal oxidants
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The 4-AcNH-TEMPO-catalyzed oxidation of D-glucose to D-glucaric acid using elemental chlorine or bromine as the terminal oxidant is reported. The pH and temperature of the reactions were closely controlled to be between 0-5 deg C and pH 11.5, respectively. Spectroscopically (1H NMR) determined yields of glucarate were greater than 90 percent; yields of crystalline monopotassium D-glucarate (or disodium D-glucarate), isolated and purified by precipitation, were between 70 and 85 percent. Oxidations of mannose to mannaric acid and galactose to mucic acid were also demonstrated.
- Merbouh, Nabyl,Bobbitt, James M.,Brueckner, Christian
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