IR spectroscopic studies of adiponitrile and ammonia adsorption over Ti?Sb?O catalyst

Rate constants for the aminolysis of o-(2,4-dinitrophenyl) cyclopentanone oxime with several primary alkylamines, C₂H₅NH₂–C₆H₁₃NH₂ and one secondary arylamine, purrolidine, in 11 water-acetonitrile are reported. With primary amines, base catalysis is absent, while with pyrrolidine saturation catalysis has been observed. Reduction in size of nonconjugated oxime moiety (leaving group), drastically decreases the rates. Thermodynamic parameters for these reactions have also been calculated.

---

O-(2,4-) (C₂H₅NH₂–C₆H₁₃NH₂) , , : =11. , . ( ) . .

     

Convective Instability of the Limiting Current of the Triiodide Reduction in a Vertical Channel

The instability of the limiting current of the cathodic reaction is studied in the I^– ₃–I^–/Pt system with excess of potassium iodide at the electrode situated at the bottom of a vertical cylindrical channel. Dependence of parameters of the oscillation process on the concentration of electroactive and supporting ions and solution viscosity is analyzed. The deceleration of the transport processes in solutions containing glycerol is shown to be due to a considerable decrease in the triiodide ion diffusion coefficient.     

Synthesis and Spectroscopic Study of Iron(III) and Copper(II) Chloride Complexes with 2-(3,3-Dimethyl-1,2,3,4-tetrahydroisoquinolylidene-1)-5,5-dimethyl-2,3,5,6-tetrahydroimidazo[2,1-a]isoquinoline-3-one (L). The Crystal Structure of L

Complexes of Fe(III) and Cu(II) chlorides with 2-(3,3,-dimethyl-1,2,3,4-tetrahydroisoquinolylidene-1)-5,5-dimethyl-2,3,5,6-tetrahydroimidazo[2,1-a]isoquinoline-3-one (L) were synthesized and studied by IR and electronic absorption spectroscopy. X-ray diffraction analysis of compound L was carried out. The molecule of L was found to crystallize in the form of cis-isomer with the proton localized on the nitrogen atom of the dihydroisoquinoline fragment.     

Synthesis and spectroscopic studies of non-heme diiron(III) species with a terminal hydroperoxide ligand: models for hemerythrin

Two compounds, [Fe2(mu-OH)(mu-Ph4DBA)(TMEDA)2(OTf)] (4) and [Fe2(mu-OH)(mu-Ph4DBA)(DPE)2(OTf)] (7), where Ph4DBA(2-) is the dinucleating bis(carboxylate) ligand dibenzofuran-4,6-bis(diphenylacetate), have been prepared as synthetic models for the dioxygen-binding non-heme diiron protein hemerythrin (Hr). X-ray crystallography reveals that, in the solid state, these compounds contain the asymmetric coordination environment found at the diiron center in the reduced form of the protein, deoxyHr. M?ssbauer spectra of the models (4, delta = 1.21(2), DeltaE(Q) = 2.87(2) mm s(-1); 7, delta(av) = 1.23(1), DeltaE(Qav) = 2.79(1) mm s(-1)) and deoxyHr (delta = 1.19, DeltaE(Q) = 2.81 mm s(-1)) are also in good agreement. Oxygenation of the diiron(II) complexes dissolved in CH2Cl2 containing 3 equiv of N-MeIm (4) or neat EtCN (7) at -78 degrees C affords a red-orange solution with optical bands at 336 nm (7300 M(-1) cm(-1)) and 470 nm (2600 M(-1) cm(-1)) for 4 and at 334 nm (6400 M(-1) cm(-1)) and 484 nm (2350 M(-1) cm(-1)) for 7. These spectra are remarkably similar to that of oxyHr, 330 nm (6800 M(-1) cm(-1)) and 500 nm (2200 M(-1) cm(-1)). The electron paramagnetic resonance (EPR) spectrum of the cryoreduced, mixed-valence dioxygen adduct of 7 displays properties consistent with a (mu-oxo)diiron(II,III) core. An investigation of 7 and its dioxygen-bound adduct by extended X-ray absorption fine structure (EXAFS) spectroscopy indicates that the oxidized species contains a (mu-oxo)diiron(III) core with iron-ligand distances in agreement with those expected for oxide, carboxylate, and amine/hydroperoxide donor atoms. The analogous cobalt complex [Co2(mu-OH)(mu-Ph4DBA)(TMEDA)2(OTf)] (6) was synthesized and structurally characterized, but it was unreactive toward dioxygen.     

The hydration of hydrophobic substances

A model of the hydration of hydrophobic substances in water is suggested. The models of fluctuation formation of empty cavities in water as a stage of hydration extensively used in the literature were shown to be at variance with experiment. The fundamental role played by the interphase boundary surface was emphasized. On this surface, the successive addition of water molecules with the formation of capsules around hydrophobic molecules occurred. The physical meaning of the Ostwald equation was revealed. This equation characterized the distribution of hydrophobic volatile substances between the gas and aqueous phases. The method of optical probes (hydrophobic aromatic molecules) was used to reveal the synergistic character of autocorrelation of dispersion interactions between water and hydrophobic substance molecules. This synergism was at variance with the Lennard-Jones potential. The synergism (superadditivity) of dispersion attraction forces, which strengthened their directional character, caused the self-organization and enhanced stability of hydration capsules with encapsulated hydrophobic molecules. Computer models were used to show that the spatially directional character of dispersion interactions necessary for the self-organization of hydrated aggregates could be simulated by the molecular mechanics method on the basis of orientational correlation of water molecules and hydrophobic substances in the starting system.     

The influence of grafted functional groups on the adsorption properties of silica

The adsorption properties of silica gel with grafted aminopropyl and guanidinoethanethiol (GET) groups were studied by the techniques of adsorption under static conditions and gas chromatography. It was shown that molecules capable of forming hydrogen bonds are adsorbed on all modified samples more weakly than on the initial silica gel. The grafting of GET radicals on the surface results in a noticiable increase in the dispersion interaction with adsorbed molecules. Calculation of the contributions of molecular groups to the constant of adsorption equilibrium showed that the thermodynamic characteristics of adsorption on aminosilochromes and aminosilicas with a polymeric layer of the modifying agent have similar values. Such adsorbents can be used for investigation of polar compounds, including organic bases. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 3, pp. 452–457, March, 1997.     

Promoting effect of potassium on catalytic and surface properties and phase commposition of catalysts for synthesis of alcohols

The dependence between catalytic and surface acid-base properties of Zn–Cr–K catalysts has been established. Modification by potassium and an increase in potassium concentration promotes Zn–Cr–K reduction and raises the yield of higher alcohols. The spinel structure of catalysts is preserved.

---

Zn–Cr–K . Zn–Cr–K , .

     

Investigation of the state of copper cations in CuCr2O4/Al2O3 catalysts based on the IR spectra of adsorbed carbon monoxide

The state of copper cations in samples of CuCr₂O₄ applied on A1₂O₃, has been investigated by means of the IR spectroscopy of adsorbed molecules. The IR spectra of carbon monoxide, adsorbed on CuCr₂O₄/Al₂O₃ catalysts and submitted to different treatments, have been studied. The separation of a Cr₂O₃ phase was observed during heating of the sample under reducing conditions with the formation of a copper-containing compound, in which the state of the copper ions was different from the state characteristic for chromite. A change in the phase composition of the active component was established in comparison with the original samples and a change in the phase composition of the support from -Al₂O₃ to -Al₂O₃ in catalyst samples, spent in catalytic heat generators.Translated from Teoreticheskaya i Éksperimental/naya Khimiya, Vol. 26, No. 5, pp. 633–637, September–October, 1990.The authors wish to express their gratitude to T. A. Gordymova and B. A. Bunimovich for their assistance in the experimental work.     

Properties of continuous mappings of unbounded metric spaces

Suppose a closed unbounded set F R_n is a union of a finite number p of closed unbounded sets F_i that are pairwise disjoint, and suppose f is a continuous mapping of F into the metric space R⁽²⁾. With each set F_i there is associated a point at infinity _i, at which it is assumed that f has a finite limit A_i R⁽²⁾, i=1, 2, ..., p. It is proved that: 1) f is bounded on F; 2) if f is a real functional, then the set contains a smallest and a largest value; 3) if the distance between F_i and F_j is greater than zero whenever i j, then f is uniformly continuous on F.Translated from Ukrainskii Matematicheskii Zhurnal, Vol. 43, No. 3, pp. 422–427, March, 1991.