Abstract: A process for preparing a difunctional compound having high enantiomeric purity that is a 1,2-, 1,3-, or 1,4-diol, dithiol, or mercapto alcohol from an optically active starting material that includes an .alpha.-, .beta.-, or .gamma.-hydroxy (or mercapto) aldehyde, ketone, ester, or amide is described. The process is carried out in an anhydrous solvent medium and comprises (1) reducing the starting material with a metal hydride (e.g., sodium borohydride), (2) adding a coreactant that is substituted by at least one, but preferably two, hydroxyl or mercapto groups (e.g., pyrocatechol), and (3) directly distilling the product from the reaction medium. The coreactant preferably has a higher boiling point at normal atmospheric pressure than the difunctional compound. The difunctional compounds are used as reactants for syntheses of agrochemicals or pharmaceuticals, or as precursors for polymers.

Abstract: "Esters" are synthesized by reacting a nucleophile with a propargyl xanthate advantageously having the formula (I):R.sub.3 --C.tbd.C--CR.sub.1 R.sub.2 --S--CS--Y--R (I)in the presence of at least one acid, Bronsted or otherwise, and at a temperature ranging from 0.degree. to 300.degree. C.; the subject reaction is particularly applicable to a wide variety of chiral organic syntheses.

Abstract: The present invention relates to a composition which can be used as reduction catalyst.This composition is characterized in that it comprises a support whose constituent material comprises at least one oxide chosen from oxides which are inert or capable of being made inert relative to the reaction mixture and a phase at least partially covering the said support, of which at least part comprises an intermetallic ruthenium-tin compound of composition Ru.sub.3 Sn.sub.7. The invention also describes the use of the reduction catalyst and its application to organic synthesis.

Abstract: Aqueous silicone dispersions crosslinkable into elastomeric state by elimination of water therefrom, well adapted for the production of elastomer seals, e.g., for the building industry, include:(A) 100 parts by weight of an oil-in-water emulsion of an .alpha.,.omega.-(dihydroxy)polydiorganosiloxane stabilized with at least one anionic or nonionic surface-active agent, or mixture thereof;(B) 1 to 100 parts by weight of an hydroxylated silicone resin containing, per molecule, at least two different recurring structural units selected from among those of the formulae: R.sub.3 SiO.sub.0.5, R.sub.2 SiO, RSiO.sub.1.5 and SiO.sub.2, wherein the radicals R, which may be identical or different, are vinyl, phenyl or 3,3,3-trifluoropropyl radicals, or linear or branched chain alkyl radicals containing from 1 to 6 carbon atoms, said resin having a hydroxyl group weight content of from 0.1% to 10%;(C) 0 to 250 parts by weight of a nonsiliceous inorganic filler;(D) 0.

Abstract: Precipitated silica particulates having a BET specific surface ranging from 20 to 300 m.sup.2 /g, a CTAB specific surface ranging from 10 to 200 m.sup.2 /g, an oil uptake (DBP) ranging from 80 to 400 cm.sup.3 /100 g, a pore volume ranging from 1 to 10 cm.sup.3 /g and a mean pore diameter ranging from 10 to 50 nm, well adapted for such applications as the coating of paper and catalysis, are prepared by (a) simultaneously introducing a silicate and an acid into a dispersion of colloidal silica, thereby providing a silica suspension, (b) next decreasing the pH of such suspension to a value ranging from 3 to 7, and (c) then separating the silica particulates from the final suspension and drying them.

Abstract: Unique colorant compositions, well suited for the pigmentation of a wide variety of coatings and substrates, e.g., cosmetics, plastics, paints and rubbers, comprise (1) at least one crystalline rare earth metal sulfide or sesquisulfide, for example cubic cerium sesquisulfide Ce.sub.2 S.sub.3, and (2) a dopant amount of at least one alkali metal, and wherein the at least one rare earth metal sulfide or sesquisulfide comprises whole (unground) monocrystalline grains thereof having a mean particle size of at most 1.5 .mu.m.

Abstract: The invention relates to the use as a luminophor in plasma systems of a compound based on an yttrium, lanthanum, gadolinium or lutecium phosphate doped with at least one rare earth chosen from the group comprising terbium, praseodymium, europium and cerium.

Abstract: The invention relates to a new process for the preparation of precipitated silica which has a good dispersibility and very satisfactory reinforcing properties. It also relates to new precipitated silicas which are in the form of powder, of substantially spherical beads or of granules, these silicas being characterized by the fact that they have a CTAB specific surface of between 90 and 250 m.sup.2 /g, a BET specific surface of between 90 and 250 m.sup.2 /g, a DOP oil uptake lower than 300 ml/100 g, a zinc content of between 1 and 5% by weight, and by the fact that the number N of stearic acid molecules consumed per nm.sup.2 of silica surface, when stearic acid is reacted with this silica in xylene for 2 hours at 120.degree. C., is at least 1. The invention also relates to the use of the said silicas as reinforcing fillers for elastomers, especially for improving their rheological properties.

Abstract: A process and reagent for allylating a nucleophile preferably of formula (V).(R).sub.n Ar--Y--H (V)The nucleophile is reacted with a reagent containing an allyl derivative and a catalyst in an aqueous phase containing at least one element of group VIII of the Classification of the elements. A water-soluble phosphine may also be present in the reagent, and the reagent may also contain at least one organic phase.

Abstract: The present invention relates to silicas, in particular precipitated silicas, which can be used in particular as abrasive agents in toothpaste compositions. The silicas according to the invention have, first of all, low specific surfaces. Their BET specific surface is between 20 and 75 m.sup.2 /g, preferably between 35 and 64 m.sup.2 /g. The invention also relates to a process for their preparation and to the toothpaste compositions containing them.

Abstract: The present invention relates to compounds composed essentially of a linear, cyclic or branched polyorganosiloxane having, per molecule, at least 3 siloxy units, including at least one siloxy functional unit of formula: ##STR1## where R.sup.1 represents a C.sub.1 to C.sub.4 alkyl or phenyl radical, X contains an N,N'-di- and/or trisubstituted phenylenediamine functional group, bonded to the silicon via an Si-(hydrocarbon linking unit)-N and/or Si-(hydrocarbon linking unit)-C bond, and a is a number chosen from 0, 1 and 2. The present invention also relates to the use of such compounds as antiozonants for rubbers and in particular for rubber compositions for tires.

Abstract: The invention relates to new compositions based on ceric oxide having an improved oxygen storage capacity, these compositions being characterized in that they contain, besides ceric oxide, at least one oxide of another metallic element M chosen from the group consisting of iron, bismuth, nickel, tin and chromium or one of their mixtures, this oxide preferably being in solid solution with the abovementioned cerium oxide. The process of synthesis of these compositions consists in first of all preparing an intimate mixture between (i) a ceric oxide or a ceric hydroxide and (ii) at least one additive consisting of a hydroxide or a salt, thermally decomposable to an oxide, of the metallic element M, and in then calcining this mixture so as to obtain the desired composition based on oxides. The compositions according to the invention are particularly useful in the manufacture of catalysts and/or catalyst supports, especially those intended for treating exhaust gases from internal combustion engines.

Abstract: In a first embodiment of the invention, a colloidal dispersion of a cerium compound is characterised in that it has a pH of at least 4 and a conductivity of at most 5 mS/cm. In a second embodiment, the colloidal dispersion is characterised in that it has a pH of more than 5. In a third embodiment, the colloidal dispersion is characterised in that the colloids have a carbon content such that the carbon/cerium mole ratio is at Least 0.01 and in that the pH is greater than 5.A process for the preparation of these dispersions is characterised in that a first colloidal dispersion is used as a starting material, with a pH which is lower than the pH of the dispersion which is to be prepared, and the pH of the first dispersion is raised while reducing the ionic strength. For the third embodiment, an organic acid is added to the starting dispersion.

Abstract: The present invention relates to water-redispersible pulverulent composition comprising:a powder of at least one water-insoluble film-forming polymer prepared from at least one ethylenically unsaturated monomer,at least one nonionic surfactant chosen from the polyoxyalkylenated derivatives,at least one water-soluble compound chosen from polyelectrolytes belonging to the family of weak polyacids.

Abstract: The invention relates to the use as a luminophor in plasma systems of a compound based on an yttrium, lanthanum, gadolinium or lutecium phosphate doped with at least one rare earth chosen from the group comprising terbium, praseodymium, europium and cerium.

Abstract: A stripping and/or cleaning composition is disclosed, which contains, by volume: (a) 1 to 90% of at least one C.sub.1 -C.sub.4 dialkyl ester of at least one C.sub.4 -C.sub.6 aliphatic diacid; and (b) 99 to 1% of at least one ether selected from the group consisting of ethers with a flash point above 5.degree. C., at least one methoxy group per molecule and a molecular weight of less than 200.

Abstract: The present invention relates to a process for the purification of a medium containing organic waste. The process according to the present invention is characterized in that the starting medium (or effluent) containing the organic waste is subjected to the following stages: (i) treatment with at least one oxidizing agent; (ii) treatment with at least one flocculating agent; (iii) treatment with at least one polyelectrolyte, and in that the effluent obtained on conclusion of all of these stages is subjected to a filtration stage (iv), whereby a filtration cake and a filtrate are obtained. The process according to the present invention is more particularly useful for the treatment of pig manure.

Abstract: The invention relates to a self-levelling fluid mortar including calcium sulphate, granulates, lime, water and either a silica and a compound containing alumina or a pozzuolana, and to a screed obtained from said fluid mortar. It also relates to the combined use of lime and either of a silica and of a compound containing alumina or a pozzuolana to increase the mechanical strength and reduce the water sensitivity of a screed.

Abstract: An aqueous emulsion comprising at least one (co)polymer is provided. The (co)polymer is derived from a monomer having formula (1):(R.sub.1 R.sub.2 C.dbd.CR.sub.3 --CO--L--).sub.q A(--NCOblock).sub.p (1)wherein R.sub.1, R.sub.2, and R.sub.3, which are the same or different, represent a hydrogen or a group selected from hydrocarbon chains comprising 1 to 12 carbon atoms, halogens, and electron-withdrawing functional groups; L, which is the same or different, represents a divalent hydrocarbon radical comprising 2 to 12 carbon atoms; A represents an organic backbone which has n free valencies, n is a number between 2 and 7, and is equal to p+q; NCOblock represents a protected isocyanate functional group; p is a number between 1 and 6; and q is a number between 1 and 6.

Abstract: The invention concerns a procedure for preparation of a precursor of a mixed cerium and zirconium oxide-based composition, characterized by the following steps:a liquid mixture is prepared containing cerium and zirconium compounds;the preceding mixture is placed in contact with carbonate or bicarbonate, thus forming a reactive medium exhibiting a neutral or basic pH during the reaction;the precipitate obtained is collected.A mixed cerium and zirconium oxide-based composition is obtained by calcining this precursor. This composition is characterized by the fact that it has a total pore volume of at least 0.6 cm.sup.3 /g, and that at least 40%, and more particularly at least 50%, of the total pore volume is composed of pores having a diameter of at most 1 .mu.m.