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1.
The diacetylenic adducts, Fe2(CO)6{-EC(H) = C(C CMe)E} (E = E, E E; E, E = S, Se, Te) (1–8) have been obtained from the room temperature stirring of Fe2(CO)6(-EE) with HC CC CMe in methanol solvent containing sodium acetate. Compounds 1–8 have been characterized by IR and multinuclear NMR (1H, 13C, 77Se, and l25Te) spectroscopy. Trends in the chemical shifts of 77Se and 125Te NMR spectra of Fe2(CO)6{-EC(H) = C(C CMe)E} with a variation of EE are discussed. 相似文献
2.
B. T. Ibragimov S. A. Talipov T. F. ARIPOV A. S. SADYKOV 《Journal of inclusion phenomena and macrocyclic chemistry》1990,8(3):323-332
The crystal structure of a 2: 1 inclusion complex of gossypol withm-xylene has been determined by X-ray structure analysis. The crystals of C30H30O8·0.5C8 H10 are triclinic, space groupPl–,a = 8.478(1),b = 14.087(2),c = 14.411(2) Å, = 115,39(1), = 75.11(1), = 86.80(1)°,V = 1475.2(4) Å3,Z = 2,D
x
= 1.29 g cm–3,T = 295 K, (CuK
) = 7.01 cm–1. The structure has been solved by direct methods and refined to the finalR value of 0.079 for 3910 observed reflections. The gossypol molecules are linked by intermolecular hydrogen bonds and form bimolecular layers parallel to the ab plane. Disorderedm-xylene molecules occupy cavities between these layers. All polar groups of the gossypol molecule are packed in the interior of the bilayer while non-polar groups are directed outwards. An analysis of the crystal packing of other inclusion complexes of gossypol shows that such bilayers are formed in four complexes and three of those structures are generically related to each other.Deceased. 相似文献
3.
A new method for molecular structure quantitation is described, in which both electronic and topological attributes are united. The method uses the hydrogen-suppressed skeleton to represent the structure and leads to a graph invariant index for the individual atoms and hydride groups of the molecular skeleton. An intrinsic atom value is calculated for each atom asI = (
+ 1)/, in which
and are the counts of valence and sigma electrons of atoms in the molecular skeleton, that is, exclusive of bonds to hydrogen atoms. The electrotopological state valueS
i for an atomi is defined asS
i =I
i + I
i, where the influence of atom j on atom i, I
i, is given as (I
i-j
j)/r
2;r is the graph separation between atoms i and j, counted as number of atoms, includingi andj. The information in the electrotopological state values is revealed by examples of various types of organic structures, including chain branching and heteroatom variation. The relation of the E-state value to NMR chemical shift is demonstrated for a series of carbonyl compounds. 相似文献
4.
Tomislav P. Živković 《Journal of mathematical chemistry》2000,28(1-3):287-312
Linear (planar) molecules A and B which are identical except for isotopic substitutions at the atomic sites are considered. Stretching (bending, out-of-plane) frequencies
k
and normal modes
k
of the isotopically perturbed molecule B are expressed in terms of stretching (bending, out-of-plane) frequencies
i
and the corresponding normal modes
i
of the unperturbed molecule A. Complete specification of the unperturbed normal modes is not required. All that is needed are stretching (bending, out-of-plane) amplitudes |
i
of the normal modes
i
at those sites that are affected by isotopic substitution. The rule which interlaces frequencies
k
of molecule A with frequencies
i
of molecule B is derived. Given two isotopic molecules A and B
that differ by a single isotopic substitution at site , the inversion relation is derived. This relation expresses unperturbed stretching (bending, out-of-plane) amplitudes at the site in terms of stretching (bending, out-of-plane) frequencies of molecules A and B
. As an example, out-of-plane vibrations of deuterated bromoethene were considered. In the simplest method 12 out-of-plane frequencies of four polydeuterated bromoethenes were calculated from 12 out-of-plane frequencies of bromoethene and three monodeuterated bromoethenes. Standard deviation of thus calculated frequencies from experimental frequencies is =2.74 cm–1. In another method, 15 out-of-plane frequencies of four polydeuterated bromoethenes and selected monodeuterated bromoethene are calculated from 9 out-of-plane frequencies of bromoethene and the remaining two monodeuterated bromoethenes. Depending on which monodeuterated bromoethene is selected (1-, cis- or trans-), standard deviation of thus obtained frequencies from experimental frequencies is 1=2.84 cm–1, c=2.96 cm–1 and t=2.72 cm–1. 相似文献
5.
M. Ataman 《Colloid and polymer science》1987,265(1):19-25
The determination of the properties of aqueous salt solutions of poly(ethylene oxide) has been extended to the cloud point, and temperature measurements have been made at several concentrations for various salts (flourides, iodides, acetates, formates, phosphates, bromides, thiosulfates and perchlorates). The resulting dependency of the critical temperatures (mostly between 290–350 K) on the molar concentration can be expressed as sequences showing the decreasing effect of anion species or cation species in salting out the polymer. The decreasing order of effectiveness of the anions in reducing the temperature is PO
4
> HPO
4
> S2O
3
> H2PO
4
–
>F– > HCOO– > CH3COO– > Br– > I–. The order for cations is K+ Rb+ Na+ Cs+ > Sr++ > Ba++ Ca++ > NH
4
+
> Li+. The changes brought about in temperatures by the salts were found to be the results of the changes taking place in the hydrophilic and hydrophobic interactions among polymer, solvent and additive salts and of the change of water structure by structure making or structure breaking ions, and of the influence of salts on the hydration sheath of the polymer. 相似文献
6.
Jerome A. Imonigie Donal H. Macartney 《Journal of inclusion phenomena and macrocyclic chemistry》1993,15(2):195-203
The effects of -, -, dm-(heptakis(2,6-di-O-methyl)--) and -cyclodextrins (CD) on the kinetics of the electron-transfer reaction of the ferrocenemonocarboxylate anion (FCA–) with bis(pyridine-2,6-dicarboxylato)cobaltate(III) have been investigated in aqueous solution (0.20 M Na2HPO4, pH 9.2) at 25.0°C. Substantial decreases in the rate constants for the electron-transfer reactions were observed upon cyclodextrin inclusion of the reductant, due to an increase in the FCA0/– reduction potential and to the insulation of the reductant from oxidant. The inclusion stability constants for {FCA·CD}– were evaluated from the1H NMR and kinetic data, and the order of the stability constants was found to be -CDdm-CD-CD>-CD. 相似文献
7.
Bolko Brauser 《Fresenius' Journal of Analytical Chemistry》1968,237(1):8-17
Zusammenfassung Eine Methode zur Differentialspektrophotometrie durch Modulation eines Monochromators wird beschrieben. Der Monochromator oscilliert mit variabler Bandbreite zwischen
1 und (
1+). Wenn (
1+) die Wellenlänge des Absorptionsmaximums ist, erscheint am Photo multiplierausgang einer Sinuswelle, deren Amplitude der Extinktions differenz zwischen
1 und (
1+) proportional ist. Die Schaltung zur ultralinearen Messung dieser Amplitude ist angegeben und ihre Anwendung mit dem Zweistrahlphotometer Rapidspektroskop gezeigt. Die Empfindlichkeit wird durch die Kombination um den Faktor 10 bis 100 gesteigert. Der Rauschpegel ist bei der Monochromator-Modulationstechnik etwa 10–4 E.Das Differentialspektrum stellt die erste Ableitung eines Spektrums dar und gestattet die genauere Lokalisation von Schultern in steilen Flanken eines Spektrums. Die Kombination der beschriebenen Methode mit der Technik des Rapidspektroskops erlaubt es, dasselbe mit gleichem Erfolg wie ein Dual-Wavelength-Gerät einzusetzen.
Summary A method for differential spectrophotometry by modulation of a single monochromator is described. A single monochromator oscillates with variable bandwidth between 1 and ( 1+ ). If ( 1 + ) is the wavelength at maximal optical density, the photomultiplier output gives a sinus-wave, the amplitude of which is proportional to the optical density difference between 1 and ( 1+). The circuit for ultralinear measurement of this amplitude is described and details of its application with the split-beam spectrophotometer Rapidspektroskop are given. The sensitivity of the entire assembly is increased by a factor of between ten and one hundred. The noise level of the monochromator-modulated technique is about 10–4 optical density units. The differential spectrum represents the first derivative of a spectrum and allows one to determine more exactly the location of shoulders in the slope of a spectrum.The combination of the described method with the techniques of the Rapid spektroskop thus provides facilities which equal those of a dual-wavelength apparatus.相似文献
8.
Vinod K. Ahluwalia Manjula Khanna Rishi P. Singh 《Monatshefte für Chemie / Chemical Monthly》1982,113(2):197-200
Obtusinin (1) has been synthesised by the reaction of 6-methoxy-7-(3-methylbut-2-enyloxy)-2H-1-benzopyran-2-one (3) with OsO4. Synthesis of 7-(3-hydroxymethylbut-2-enyloxy)-6-methoxy-2H-1-benzopyran-2-one (2) has been achieved by the regiospecific oxidation of3 with SeO2 followed by reduction of the formed aldehyde with KBH4.
Synthese von Obtusinin und 7-(3-Hydroxymethylbut-2-enyloxy)-6-methoxy-2H-1-benzopyran-2-on
Zusammenfassung Obtusinin (1) wurde über 6-Methoxy-7-(3-methylbut-2-enyloxy)-2H-1-benzopyran-2-on (3) mit OsO4 synthetisiert. Die Darstellung von 7-(3-Hydroxymethylbut-2-enyloxy)-6-methoxy-2H-1-benzopyran-2-on (2) wurde mittels regioselektiver Oxidation von3 mit SeO2, gefolgt von Reduktion des gebildeten Aldehyds mit KBH4, bewerkstelligt.相似文献
9.
Ab initio SCF-MO-LCAO calculations have been performed with a 7s3p/3s GTO basis set for the CH3O--lactam + OH– reaction which is related to the mode of action of -lactam antibiotics. The comparison of the present results with the previous ones for -lactam + OH– and 3-cephem + OH– shows that the CH3O substitution has a negligible effect on the amidic bond breaking of -lactam, so that this group probably influences other steps of the antibiotic reactivity of cephaloporins. 相似文献
10.
M. Belger 《Journal of mathematical chemistry》1994,16(1):367-388
For a crystallographic group
acting on ann-dimensional Euclidean space we consider the
-invariant linear elliptic differential operatorP with constant coefficients and to it the
-automorphic eigenvalue problemP [] + = 0. N() is the number of all eigenvalues smaller than or equal to the frequency bound
q (q: order ofP). Earlier we found the asymptotic estimationN() c0 · n + c1 · n–1 (c
0,c
1: certain volumina). Furthermore,N() was interpreted as the number of so-called principal classes of principal lattice vectors within a convex domain. In this paper we demonstrate these results for the casen = 2 for two representative crystallographic groups
and the assigned lattices. Above all we demonstrate a counting method for an exact estimation ofN() if a is not too big. In an analogous way we can treat all the 230 space groups of crystallography. It will be seen that these applications are brought about by the so-called principal vectors of these lattices. 相似文献
11.
John F. Corrigan Marie Dinardo Simon Doherty Arthur J. Carty 《Journal of Cluster Science》1992,3(3):313-332
Tetrametal clusters such as Ru4(CO)13(-PPh2)2 and Ru4(CO)10(-PPh2)4 are 64-electron systems and, with five metal-metal interactions, are formally electron rich. In fact these clusters have unusual rhomboidal (or flat butterfly) structures with three or four elongated Ru-Ru bonds. With molecular orbitals antibonding with respect to metal metal interactions occupied in such clusters, facile two electron oxidation or ligand dissociation processes should occur, giving electron precise molecules. The molecule Ru4(CO)13(-PPh2)2
1a undergoes a remarkable, reversible transformation upon loss of CO affording (-H)Ru4(CO)10(-PPh2)[4-1(P),1(P),1(P),1,2-{C6H4}PPh]3 a cluster which contains a five coordinate phosphido bridge and an orthometallated 2 arene ring. This conversion is reversible under CO. These and other results which will be discussed confirm that M4 clusters with electrons in excess of the expected EAN rule count may exhibit unusual reactivity. The solid-state CP/MAS and static powder31P NMR spectra of some of these clusters exhibit99/101Ru-31P couplings, values of which have been measured for the first time. 相似文献
12.
Toshikatsu Koga 《Theoretical chemistry accounts》1989,75(6):417-424
Based on momentum- and position-space analyses of the moment operators for two-electron atoms, it is shown that there exists a family of two-electron wave functions which satisfy a proportionality relation, r/
1
v
/r
12
v
=p/
1
v
/p
12
v
=2–v/2, between the one and two-electron moments in position and momentum spaces, where v is an arbitrary number for which the moments are well-defined. 相似文献
13.
A comparative analysis of the relative reactivities of N-arylimides of endo-and exobicyclo[2,2,1]hept-5-ene-2,3-dicarboxylic acids for the addition reactions of hexachlorocyclopentadiene and bromine has been carried out. According to different correlations the transition states of these two processes are shown to be similar.
N- - - [2,2,1] -5--2,3- . .相似文献
14.
D. B. Goldman 《Journal of Thermal Analysis and Calorimetry》1985,30(5):1071-1080
Temperature programmed reduction in a hydrogen flow with simultaneous evolved gas analysis was employed to determine surface oxides on oxide dispersion strengthened (ODS) nickel containing TiO2, A12O3 or Cr2O3 particles, and on a Ni-2OCr alloy, after exposure to air at elevated temperatures. Oxides on particles of water-atomized (WA) Ni-2OCr powder were analysed similarly. Significant differences in starting temperatures of the reaction between hydrogen and phases present in oxide layers made identification of the phases possible. NiO or NiO doped with Ti, Al or Cr are the major constituents of the scale formed on ODS Ni. NiTiO3, NiCr2O4 and NiAl2O4 are formed as a result of a reaction between TiO2, A12O3 or Cr2O3 particles in the scale with NiO. The oxide layer formed on Ni-2OCr alloy consists of Cr2O3 and of NiO doped with Cr. Surface oxides on WA Ni-2OCr contain Cr2O3 and a small amount of NiO.
Zusammenfassung Temperaturprogrammierte Reduktion im Wasserstoffstrom wurde zusammen mit gleichzeitiger Analyse des in Freiheit gesetzten Gases dazu benutzt, um Oberflächenoxide an Nickel enthaltenden TiO2-, A12O3- oder Cr2O3-Partikeln mit verstärkter Oxiddispersion (ODS) und an einer Ni-2OCr-Legierung nach Behandlung in Luft bei erhöhten Temperaturen zu bestimmen. Oxide auf Partikeln von wasser-zerstäubtem (WA) Ni-2OCr-Pulver wurden auf ähnliche Weise analysiert. Signifikante Unterschiede in der Starttemperatur der Reaktionen zwischen Wasserstoff und der in den Oxidschichten vorliegenden Phasen ermöglichen die Identifikation der Phasen. NiO oder mit Ti, Al oder Cr gedoptes NiO sind die Hauptbestandteile des auf ODS-Ni gebildeten Belags. NiTiO3, NiCr2O4 und NiAl2O4 treten als Produkte der Reaktion von TiO2-, Al2O3- oder Cr2O3-Partikeln mit NiO im Belag auf. Die auf der Ni-2OCr-Legierung gebildete Oxidschicht besteht aus Cr2O3 und aus mit Cr gedoptem NiO. Oberflächenoxide auf WA-Ni2OCr enthalten Cr2O2 und geringe Mengen an NiO.
- , , , , , , Ni-2r, . Ni-2OCr. , , . , , , , . NiTiO3, NiCr2O4 NiAl2O4 , , . , Ni-2r, , . Ni-2r .相似文献
15.
G. V. Nizova Jacques Muzart G. B. Shulpin 《Reaction Kinetics and Catalysis Letters》1991,45(2):173-178
Cyclohexane is oxidized by air oxygen in CH2Cl2 solution to yield cyclohexanol, cyclohexanone and cyclohexyl chloride when irradiated by light (>310 nm) in the presence of (Bu4N)2CrO4 or (Bu3SnO)2CrO2. The addition of PhIO greatly accelerates the reaction and increases the yield of products. The reaction mixture contains neither cyclohexanol nor cyclohexanone when the photoreaction in the presence of the Cr(VI)–PhIO system is carried out in argon atmosphere. Hence neither iodosylbenzene nor oxochromium compounds can be oxygen atom donors in alkane oxygenation. The accelerating effect of iodosylbenzene may be due to the enhanced oxidizing power of photo-excited oxochromium species when coordinated to iodosylbenzene.
CH2Cl2 , , (>310 ) (Bu4N)2CrO4 (Bu3SnO)2CrO2. PhIO . Cr(VI)–PhIO , , . , ( ) . .相似文献
16.
The doping of MnO2 with small quantities of Bi2O3 results in an increase of the surface oxygen bond energy. Accordingly, the values of the specific catalytic activity and selectivity to nitrous oxide are lower for the doped catalyst than for pure MnO2. The mechanism of low temperature ammonia oxidation is the same on both catalysts.
Bi2O3 MnO2 . , , MnO2. .相似文献
17.
R. I. Soltanov E. A. Paukshtis E. N. Yurchenko 《Reaction Kinetics and Catalysis Letters》1985,28(1):139-144
Influence of the strength and concentration of non protic centers on the catalytic activity of metal-zeolite catalysts in isomerization of n-butane has been studied. A relationship between the specific activity and the center strength is suggested.
-. , .相似文献
18.
The reaction of phenylacetylene with CO and n-butanol in toluene (363 K) catalyzed by the Pd(dba)2/m(CF3COOH)/n(Ph3P) system (dba is dibenzylideneacetone; 2 m 8; 10 n 30) is studied. The initial rate of the main product (butyl 2-phenylpropenoate) buildup is found to depend on the pressure of CO and the concentrations of reactants and system components. The state of the catalyst under reaction conditions is studied in situby IR spectroscopy. A kinetic model is developed based on the experimental results. This model corresponds to the mechanism that resembles the hydride mechanism in the type of main intermediates in the catalytic cycle. 相似文献
19.
G. Hakvoort 《Journal of Thermal Analysis and Calorimetry》1988,33(4):1235-1240
The activity of copper containing catalysts for the formation of methanol from CO and H2 is investigated with High Pressure DSC. The activity is measured at 40 atm. and 230 C. The DSC signal has been calibrated with melting experiments with tin under reaction conditions. Comparison with flow reactor measurements shows a good relation with the DSC experiments.
We express our thanks to Dr. E. C. Kruissink and Drs. W. Glasz for delivery of the catalysts and measurement of the reactor activities. 相似文献
Zusammenfassung Die Aktivität kupferhaltiger Katalysatoren bei der Bildung von Methanol aus CO und H2 wurde mittels Hochdruck-DSC untersucht. Sie wurde bei 40 bar und 230 C gemessen.Die Eichung des DSC-Signals erfolgt mittels Schmelzen von Zinn unter Reaktionsbedingungen. Ein Vergleich mit Messungen im Strömungsreaktor zeigte eine gute Korrelation mit den DSC-Ergebnissen.
- , . 40 230. . .
We express our thanks to Dr. E. C. Kruissink and Drs. W. Glasz for delivery of the catalysts and measurement of the reactor activities. 相似文献
20.
V. A. Razdobarov V. A. Sadykov S. A. Veniaminov N. N. Bulgakov O. N. Kovalenko Yu. D. Pankratiev V. V. Popovskii G. N. Kryukova S. F. Tikhov 《Reaction Kinetics and Catalysis Letters》1988,37(1):109-114
The differentiation of surface oxygen forms of Co3O4 by energy, reactivity and centers of adsorption has been carried out.
Co3O4 , .相似文献