摘要:
Pentoses and hexoses are epimerized by heating sugar dissolved in a solvent in the presence of a molybdenum(VI) compound, by an improved process in which, for the preparation of a sugar having cis OH groups in the 2- or 3-position, of the formula Ia or Ib ##STR1## where R is one of the radicals ##STR2## a homogeneous solution of the corresponding sugar of the formula IIa or IIb ##STR3## is heated to 75.degree.-100.degree. C. in the presence of from 30 to 200 mol %, based on sugar used, of a metal salt of the formula (III)MeX.sub.2 (III)where Me is Mg, Ca, Sr, Ba or Zn and X is Cl or Br, which may or may not contain water of crystallization, and in the presence of from 2 to 20 mol %, based on the sugar used, of a molybdenum(VI) compound.The process is particularly important for the preparation of D-ribose, which is required as an intermediate for vitamin B.sub.2.
摘要:
A process for preparing polyenecarbonyl compounds having a high all-E content and their acetals or ketals by aldol condensation or Horner-Emmons reaction comprises carrying out the reaction, for the purposes of the preferred formation of a double bond of E configuration and in order to maintain the E configuration of the double bonds in the stating compounds as completely as possible, in the presence of oxygen or an oxygen-inert gas mixture or nitric oxide or a nitric oxide-inert gas mixture and/or in the presence of specific stable radicals and/or in the presence of quinones or quinone derivatives.
摘要:
Abstract of the Disclosure: Compounds of the formula I ##STR1## where R.sup.1 is H or C.sub.1 -C.sub.4 -alkyl, R.sup.2 is C.sub.1 -C.sub.4 -alkyl and R.sup.3 is an ether, silyl ether or acetal protective group which can be converted into a hydroxyl group by hydrolysis, in particular one of the radicals ##STR2## and a process for preparing these compounds by reacting an alkenyne of the formula II ##STR3## in an inert solvent in the presence of lithium amide with a cyclohexenone of the formula III ##STR4## and the use of the compounds of the formula I for preparing astaxanthin, are described.
摘要:
A process for the preparation of alkyl esters of 0,0-dialkyl-4-phosphono-2-methyl-2-butenoic acid containing a high percentage of E isomers, wherein the corresponding alkyl esters of 2-hydroxy-2-methyl-3-butenoic acid are caused to react with PBr.sub.3 or PCl.sub.3 at temperatures ranging from 0.degree. to 80.degree. C. in the absence of pyridine and, if desired, the resulting mixture comprising predominantly alkyl esters of 4-halo-2-methyl-2-butenoic acid is caused to react with trialkyl esters of phosphorous acid at temperatures ranging from 70.degree. to 140.degree. C. The end products are desirable C.sub.5 building blocks for polyene syntheses or preceding stages.
摘要:
Compounds of the formula I ##STR1## where R.sup.1 is H or C.sub.1 -C.sub.4 -alkyl,R.sup.2 is C.sub.1 -C.sub.4 -alkyl and R.sup.3 is an ether, silyl ether or acetal protective group which can be converted into a hydroxyl group by hydrolysis, in particular one of the radicals ##STR2## and a process for preparing these compounds by reacting an alkenyne of the formula II ##STR3## in an inert solvent in the presence of lithium amide with a cyclohexenone of the formula III ##STR4## and the use of the compounds of the formula I for preparing astaxanthin, are described.
摘要:
A dividing-wall column having a dividing wall which is essentially disposed along the long direction of the column is proposed, which divides the column interior into a feed part, a take off part, an upper shared column part and a lower shared column part, with feed in whole or in part in the vaporous state of a mixture to be separated between the upper region of the feed part and the lower region of the feed part and/or side stream take off in whole or in part in the vaporous state between the upper region of the take off part and the lower region of the take off part, where if feed is in whole or in part in the vaporous state the cross-sectional area of the upper region of the feed part is increased by plane-parallel displacement of the dividing wall toward the upper region of the take off part, and/or if the side stream take off is in whole or in part in the vaporous state, the cross-sectional area of the lower region of the take off part is increased by displacement of the dividing wall toward the lower region of the feed part, in such a manner that the F factor is substantially the same in all column regions.
摘要:
A column is described for carrying out reactive distillations in the presence of a heterogeneous particulate catalyst having an ordered packing or random packings which form intermediate spaces in the column interior, the quotient of the hydraulic diameter for the gas flow through the ordered packing or the random packings and the equivalent diameter of the catalyst particles being in the range from 2 to 20, preferably in the range from 5 to 10, in such a manner that the catalyst particles are introduced into the intermediate spaces, distributed and discharged loose under the action of gravity.
摘要:
Graft copolymers having improved phase binding between the graft base and the grafted-on polymer, are prepared from:a) a grafted-on polymer phase containing one or more monomers from the group consisting of (meth)acrylates of alcohols having 1 to 10 carbon atoms, vinyl esters of saturated aliphatic carboxylic acids having 2 to 10 carbon atoms, olefins, vinyl halides, styrene and styrene derivatives, andb) a peroxy group-containing copolymer phase containing from 0.01 to 20% by weight of an olefinically unsaturated peroxy compound of the general formula I or II ##STR1## where R.sup.1 is a chemical bond or a linear or branched alkyl chain having 1 to 10 carbon atoms or a cycloalkyl group having 3 to 10 carbon atoms, R.sup.2 and R.sup.3 are an alkyl group having 1 to 4 carbon atoms, R.sup.4 is an alkyl group or an alkyl-substituted phenyl group having 3 to 12 carbon atoms, and R.sup.5 is a cycloalkyl group having 3 to 12 carbon atoms, and from 80 to 99.9% by weight of one or more comonomers from the group consisting of the (meth)acrylates of alcohols having 1 to 10 carbon atoms, vinyl esters of saturated aliphatic carboxylic acids having 2 to 10 carbon atoms, olefins, vinylaromatic compounds, vinyl halides and/or vinyl ethers.The graft copolymers are useful as binders in the textile industry as heat stable binders, as adhesives in plasters and as binders in emulsion paints.