Calculus rules of the generalized contingent derivative and applications to set-valued optimization

Positivity - In the paper, we develop sum and chain rules of the generalized contingent derivative for set-valued mappings. Then, their applications to sensitivity analysis and optimality...     

Regioselectivite des substitutions nucleophiles sur des fluoro olefines fonctionnelles

The fluoroolefines CF₃C$\text{F}\text{β}$=C$\text{F}\text{α}$-Y where Y=C₆H₅, C₆H₄CF₃, CONET₂, COOC₃H₇ have been synthesized. Diethylaminolithium or lithium ethoxide attack preferentially these olefines at the α position when Y=C₆H₅ or exclusively at the β position when YCOOC₃H₇. With Y=CONEt₂ this regioselectivity is not so neat, therefore the polarising effect of CF₃ group should be not very much weaker than the amide's. The increasing of the electronic effect in the order

show that vinylic fluorine atoms have no influence on the transmission of these electronic effects.     

Condensation des bromures de perfluoro-alkylmagnesium sur les aldehydes et cetone α-halogenes

Perfluoroalkyl magnesium halides react with α halogenocarbonyl compounds producing diastereoisomeric halohydrines which lead to perfluoroalkyl epoxydes by cyclisation.NMR study shows that the epoxyde configuration may be deduced from the coupling constant value ⁴J(H-F) between the epoxyde proton and the R_F radical.The condensation on the carbonyl group is less stereo-selective with R_FMgX than with usual Grignard reagents.     

Absolute asymmetric synthesis of tertiary α-amino acids

Frozen: the spontaneous crystallization of an achiral compound in a chiral conformation is used as the unique source of chirality in an absolute asymmetric synthesis of tertiary amino acids. The dynamic axial chirality of tertiary aromatic amides is frozen in a crystal and is responsible for the stereoselectivity of the deprotonation/alkylation. α-Amino acid derivatives are synthesized in up to 96 % ee.     

Kinetics of <Emphasis Type="Italic">n</Emphasis>-hexane isomerization over supported palladium catalysts

The steady- and unsteady-state kinetics of n-hexane isomerization over Ni- or Co-promoted Pd/HZSM-5 catalysts in the presence of hydrogen has been investigated. The kinetics of the reaction is described by similar fractional rational rate equations differing in the values of their constants. Hydrogen exerts a favorable effect on the isomerization rate. The catalysts have been characterized by the BET-N₂ method, X-ray diffraction, transmission electron microscopy, H₂-TPR, and NH₃-TPD. The introduction of a promoter (Ni or Со) strengthens the adsorption of the reactants and increases the amount of reactants adsorbed.     

Dragon Fruit Foliage: An Agricultural Cellulosic Source to Extract Cellulose Nanomaterials

In this report, we focus our effort to extract cellulose nanomaterials (CNs) from an agricultural cellulosic waste, Dragon Fruit foliage (DFF). DFF was first pretreated by several mechanical treatments and then bleached by chemical treatment to obtain bleached DFF. CNs were then produced from the hydrolysis of the bleached DFF catalyzed by sulfuric acid. We obtained CNs with a small diameter (50 to 130 nm) and length (100 to 500 nm) and a height of 3 to 10 nm. The CNs have a high crystallinity (crystallinity index 84.8%), high −COOH content (0.74 mmol·g⁻¹), good thermal stability and a good Cu (II) adsorption capacity with an adsorption maximum of ~103 mg·g⁻¹. These findings demonstrated the great potential of converting many agricultural cellulosic wastes into valuable cellulose nanomaterials.     

Reaction of perfluoroalkylcarbanions with thiocyanates

A nucleophile can attack a thiocyanate either on the sulfur atom or on the cyanide group. In the former case the product is a sulfide, in the later one a nitrile.Our goal was to study this reaction with perfluoroalkyl carbanions. Linear, ramified and cyclic magnesium or potassium anions were examined. It appears that, independently of the nature of the R group (CH₃, C₆H₅CH₂, C₆H₅), attack occurs on the sulfur atom leading only to the formation of sulfides.

In the case of RC₆H₅CH₂, cleavage of the sulfide by chlorine gives mainly the corresponding perfluoroalkylsulfenyl chloride.