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1.
The complexation of esters, amides, carboxylic acids, and inorganic ions with alpha-cyclodextrin (-CD) in aqueous medium was studied by calorimetry. Thermodynamic parameters for the formation of the host–guest complex have been determined. All these processes seem to be enthalpy driven. The entire ester molecule probably penetrates the -CD cavity. The carboxylic acids hydrogen bond to the -CD while the alkyl part of the acid enters the cavity. Amides undergo only a weak interaction with the host molecule -CD. Larger anions interact more strongly with -CD than do smaller anions; this may be, in part, due to the relative ease of desolvation of the larger anion. The cation seems to play some role in the complexation process with -CD.  相似文献   

2.
A study is made of the liquid phase hydrogenation of-(-furyl)-and-(-thienyl)--nitroethylenes over Pd black. It is shown that the nature of the substituent (phenyl, furyl, thienyl) does not affect the mode of addition of the hydrogen to the nitrovinyl group. Conditions are found for catalytic synthesis of high yields of heterylacetaldehyde oximes from nitroalkenes.  相似文献   

3.
Depending on crystallization conditions, dianilinegossypol and ethylacetate form low (ambient temperature, -phase) and high temperature (t = 35°C, -phase) clathrate modifications. The structure of the -phase has been discussed earlier [1]. Crystals of the 1 : 1 -phase complex, C42H40O6N2·C4O2H8, are monoclinic, space group P21/c, a = 11.362(6), b = 19.479(9), c = 19.085(9) Å, = 103.21(4)°, V = 4112(3)Å3, Z = 4, R = 0.084 for 3210 observed reflections.In these complexes centrosymmetric dimers of dianilinegossypol molecules formed via O(5)—H···O(3) hydrogen bonds are associated into columns by a weak O(8)—H···O(7) H-bond. A difference in the structure of these two phases is in the packing mode of the columns. The angle formed by intersecting host columns is about 126° for the -phase and 104° for the -modification. Guest molecules are hydrogen bonded to the host molecules via an O(1)—H···O(10) bond and are accommodated in channels in -phase complex and in cavities in -phase complex.  相似文献   

4.
The kinetics of electroreduction of Pd(II) complexes with -alanine, Pd(ala)2, is studied on a rotating Pd disk electrode in solutions of pH 8–13 containing large excess of -alanine and various supporting electrolytes (NaF, Na2SO4, NaClO4). On a Pd electrode, complexes Pd(ala)2 undergo reduction at potentials much more negative than on an Hg electrode. This is attributed to the chemisorption of water on the Pd electrode, which hampers adsorption of Pd(ala)2 that take part in the slow electrochemical stage. As with the Hg electrode, perchlorate ions hinder the Pd(ala)2 reduction on a Pd electrode. Studying adsorption of Pd(ala)2 on a Pd electrode is hampered by parallel processes of hydrogen adsorption and absorption.  相似文献   

5.
Summary From SIMS measurements on deuterium charged niobium foils a pressure-composition isotherm was obtained. The plateau pressure of the –-two-phase region is in good agreement with that known from electrochemical p-n isotherm measurements. The solubility in the homogeneous -phase measured by SIMS, however, is enhanced compared with the electrochemical p-n isotherm, i.e. the homogeneous -phase is broadened. These results are due to the ion bombardment causing a lattice distortion within the near surface region during the SIMS experiment.  相似文献   

6.
Zusammenfassung Der Aktivierungsvorgang der Anionkatalyse der Mutarotation der -Glucose besteht nach dem Verfasser darin, daß das Wasser des hydratisierten Anions das Proton von der dem Brückensauerstoff benachbarten Hydroxylgruppe der -Glucose auf das Anion überträgt. Katalysen der Mutarotation der -Glucose durch Anionen ohne innere Wasserstoffbrückenbindung (wie Formiation) weisen dieselbe Aktivierungsenthalpie auf wie die Wasserkatalyse der Glucosemutarotation. Hingegen ist für Katalysen durch Anionen mit innerer Wasserstoffbrückenbindung ein zusätzlicher Betrag der Aktivierungsenthalpie zur Lösung der inneren Wasserstoffbrückenbindung des Anions erforderlich. Von diesem Gesichtspunkt aus werden die Enthalpie und Entropie der inneren Wasserstoffbrückenbindung des Acetations berechnet und diskutiert.
Kinetic determination of enthalpy and entropy of internalH bridges in anions
The activation of the anion catalysis of the mutarotation of the -glucose consists—according to the author—in the transfer of the proton from the hydroxyl group in vicinity of the oxygen bridge of the -glucose to the anion by the water molecule of the hydrated anion. The catalysis of the mutarotation of -glucose by anions without an internal hydrogen bridge (for example formate ion) has the same activation enthalpy as the water catalysis of the mutarotation of -glucose. But for the catalysis of the mutarotation of -glucose by anions with internal hydrogen bridges and additional amount of activation enthalpy is necessary for loosening the internal hydrogen bond of the


1. Teil der Originalmitteilung bei der Tagung der Deutschen Bunsengesellschaft in Frankfurt am Main am 16. Mai 1969.  相似文献   

7.
Conclusions The enantioselective hydrogenation of-nitrocaprolactam (I) is effected on a chiral Pd complex, obtainedin situ in the presence of S--phenylethylamine, to give S--aminocaprolactam (II), hydrolysis of which gives S-lysine. The optical yield varies from 1 to 13% according to the solvent and concentration of chiral ligand. On a Pd complex with S-N-isopropyl--phenylethylamine, enantioselective hydrogenation of (I) gives an excess of the S-enantiomer of (II) (2%). On a Pd complex with S-phenylalaninol, hydrogenation of (I) leads to the R configuration of (II) with EE 7.2%.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 7, pp. 1597–1600, July, 1987.  相似文献   

8.
Conclusions An efficient method for the synthesis of ,,-trihydropolyfluoroalkyl chlorophosphates is by reacting ,,-trihydropolyfluoroalkyl dichlorophosphites and bis-(,,-trihydropolyfluoroalkyl) phosphites with sulfuryl chloride. It has been found that in three-coordinated polyfluoroalkyl phosphites, the high electronegativity of the polyfluoroalkyl groups hinders cleavage of the latter on reaction with sulfuryl chloride, thereby facilitating the formation of oxidation products.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 1, pp. 146–149, January, 1988.  相似文献   

9.
The molecular geometries of a series of steroid hormones including cortisol, 9-fluorocortisol, 6-fluorocortisol, and 9-chlorocortisol were optimized by 3-21G and 6-31G* ab initio calculations. The results of calculations on both levels are well consistent with each other and with the experiment. The conformational changes and electron density redistribution occurring in going from cortisol to its 6- and 9-halo derivatives were discussed. A conclusion was made that the O and F atoms can participate in hydrogen bonding with the corresponding structural groups of glucocorticoid receptors.  相似文献   

10.
The intercalation of ferrocene and dimethylaminomethylferrocene into -tin(IV) hydrogen phosphate (SnP) and -vanadyl phosphate has been investigated. Successful intercalation of 0.81 mol of dimethylamino-methylferrocene into -SnP by an acid-base reaction in aqueous medium to form a bilayer of protonated amines was achieved. However, ferrocene was not intercalated under the same conditions. Intercalation of -vanadyl phosphate by 0.11 mol of ferrocene in acetonic medium at room temperature was effected by a redox topotactic reaction. The voluminous dimethylaminomethylferrocene was not intercalated into -vanadyl phosphate.  相似文献   

11.
A general characteristic of cathodic reduction of -phenylvinylphosphonic acid and its methyl- and chloro-parasubstituted derivatives on Pt/Pt, Pd/Pt, and Pd/Pt modified with Cd and Cu adatoms, is given. At effective pressures of about 103–104 Pa the processes occur at high rates and at some potentials are limited by the reactant diffusion from the bulk solution. In the presence of Cd and Cu adatoms two reduction waves (presumably, single-electron) may be isolated, i.e. the hampering by adatoms is more pronounced for a second successive stage of the process. At low effective hydrogen pressures the hydrogenation rate is higher on Pd electrodes, which possess a larger sorption capacity. Potential intervals where the reduction of substituted reactants may be complicated by destruction, are found. It is shown that -phenylvinylphosphonic acid undergoes a complete reduction with a current efficiency of 100% in both hydrochloric- and sulfuric-acid solutions. Conditions where the reduction of -(4-chlorophenyl)vinylphosphonic acid proceeds largely without destruction are found. Prospects for use of electrochemical reduction as a preparative method of a selective production of -arylethylphosphonic acids are considered.  相似文献   

12.
The influence exerted by addition of -hydroxynaphthoic acid and combined additive Hg + Pb + -hydroxynaphthoic acid on the corrosion and self-discharge of a porous zinc electrode in alkali solution was studied.  相似文献   

13.
Zusammenfassung Aus den entsprechenden -Bromestern werden durch Umsetzung mit Natriumnitrit die -Oximinodicarbonsäuredimethylester C7 und C9 und der , -Dioximinoazelainsäuredimethylester erhalten. -Methyladipinsäure wird zum Gemisch aus -Bromund -Bromester umgesetzt. Mit Natriumnitrit wird -Nitro-und -Oximino--methyladipinsäuredimethylester erhalten.
The -oximino dicarboxylic dimethyl esters of C7 and C9 and the , -dioximino azelaic acid dimethyl ester are received from the corresponding -bromo esters by reaction with sodium nitrite. -Methyladipic acid is reacted with bromine to a mixture of the -bromo and -bromo ester. Reaction with sodium nitrite gives the -nitro ester and the -oximino ester of -methyl adipic acid.


5. Mitt.:H. Reinheckel, Mh. Chem.98, 1217 (1967).  相似文献   

14.
-Cyclodextrin having cinnamamide at 6- or 3-positions (6-CiNH--CD, 3-CiNH--CD) and -cyclodextrin with cinnamamide on 6-position (6-CiNH--CD) have been prepared. Supramolecular structures were formed in the solid state or aqueous solutions and characterized by measurements of NMR and vapor pressure osmometry (VPO). The results indicate that 6-CiNH--CD formed insoluble supramolecular polymers in the solid state, while 6-CiNH--CD and 3-CiNH--CD formed supramolecular complexes in aqueous solutions. 6-CiNH--CD was found to form a dimer in an aqueous solution. 3-CiNH--CD formed intermolecular complexes to give supramolecular polymers. The differences of the position of guest part on cyclodextrins caused to give a variety of supramolecular structures in aqueous solutions.  相似文献   

15.
summary The reaction of telomerization of ethylene with carbon tetrachloride or chloroform is initiated by hexacarbonyls of chromium, molybdenum, and tungsten at 115–120, forming ,,,-tetrachloroalkanes and ,,-trichloroalkanes. respectively.  相似文献   

16.
Conclusions The structure of two triterpone glycosides fromSapindus mukorossi Gaertn. has been established. It has been shown that sapindoside A is hederagenin 3-O--L-arabinosyl-(2 1)--L-rhamnopyranoside and sapindoside B is the 3-O--L-arabopyranosyl-(2 1)-O--L-rhamnopyranosyl-(3 1)--D-xylopyranoside.  相似文献   

17.
Oxidation of tricyclic sesquiterpenoids of the caryophyllene type with the HBr—DMSO system afforded ,-unsaturated -bromoketones. Since tricyclic derivatives, unlike simple alicyclic ketones, cannot undergo aromatization, all intermediate oxidation products can be isolated, which provide evidence that oxidation proceeds according to the following scheme: ketone-bromoketone,-dibromoketone,-unsaturated -bromoketone.  相似文献   

18.
The formation of host-guest complexes of gossypol at different temperatures has been investigated for the same pressure and concentration. Gossypol forms three different clathrates with dichloromethane within the temperature interval of 22-36 °C. Single crystals of these three modifications (phases) were obtained and their crystallographic parameters measured. The structure of the -phase has been determined previously and the -phase is isostructural to the inclusion complex of gossypol with benzene, while the structure of the -phase has been solved during the present research. Crystals of C30H30O8·CH2Cl2 are triclinic, space group P1, a = 8.604(1), b = 11.858(2), c = 14.405(2) (Å), = 84.60(1), = 89.14(1), = 89.73(1)°, V = 1463(1) Å3, Z = 2, R = 0.089 for 2419 observed reflections.Under ambient conditions gossypol forms unstable tubulates of the -phase; the -phase is a stable cage-type clathrate (cryptate) and the host-guest complex of the -phase is a clathrate of intermediate tubulato-cryptate type.  相似文献   

19.
Various approaches to the synthesis of 16,17-epoxypregn-4-ene-9,21-diol-3,20-dione were studied. A preparative method was found for the synthesis of this compound by the microbiological transformations of 20,20-dimethoxy-16,17-epoxypregn-5-ene-3,21-diol using Rhodococcus sp. with subsequent removal of the dimethyl acetal protection in 20,20-dimethoxy-16,17-epoxypregn-4-ene-9,21-dio-1-3-one.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 690–693, March, 1990.  相似文献   

20.
The syntheses of the 2-anilinocyclopentanones2 a–2 e in yields about 50% by reaction of 2-chlorocyclopentanone with 4-chloroaniline, N-methyl-4-chloroaniline, ,,-trifluoro-3-toluidine, N-methyl-,,-trifluoro-3-toluidine and 3,4,5-trimethoxyaniline, are described.  相似文献   

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