Thermodynamic study of a series lithium β-diketonates

Thermal behaviour of a series of lithium β-diketonates: Li(dpm) (dpm=dipivaloylmethanate (2,2,6,6-tetramethylheptane-3,5- dionate)), Li(pta) (pta=pivaloyltrifluoracetonate (2,2-dimethyl-6,6,6-trifluoro-3,5-hexanedionate)), Li(tfa) (tfa=trifluoracetylacetonate (1,1,1-trifluoro-2,4-pentandionate)), Li(hfa) (hfa=hexafluoracetylacetonate (1,1,1,5,5,5-hexafluoro-2,4-pentandionate)) has been investigated. Gas phase composition of these complexes has been established. Temperature dependences of vapor pressure of lithium compounds were obtained by static and dynamic methods, and thermodynamic parameters were calculated. Dependence of compound volatility on ligand structure is shown. For Li(dpm) detailed investigation has been done by differential scanning calorimetry (DSC).     

Fullerene C6 0 Aggregates in Polymethyl Methacrylate Films

The structure of aggregates of fullerene C_{6 0} introduced into films of radical polymethyl methacrylate in the stage of solution preparation was studied by wide-angle X-ray diffraction.     

EPR studies of reduced Zn-chlorins and their isotope substituted analogues

Radical anions of Zn-chlorin, Zn-octaethylchlorin complexes and their ¹⁵N and deuterium substituted analogues have been studied by EPR spectroscopy and the INDO molecular orbital method in the unrestricted Hartree-Fock procedure. Parameters of experimental spectra, determined by using the iterative least-squares fitting method, have been compared with those calculated on the basis of spin density distribution. A satisfactory agreement between the experimental hyperfine coupling constants and theoretical ones for the systems studied has been obtained.     

Types of rotary crystal state of solid solutions of paraffins

Thermal deformations and polymorphous transformations of solid solutions of paraffins in C₁₇–C₁₉, C₁₉–C₂₁, C₂₁–C₂₃, C₂₂–C₂₄, and C₂₃–C₂₄ systems are investigated by thermal X-ray diffractometry using a temperature step of several tenths of a degree. It is examined how the length of a molecular chain of a homolog (n) and the difference in length (Δn) between the chains as well as the molecular composition of a solid solution affect these transitions, and the data are compared with those for the individual homologs of paraffins. St. Petersburg University. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 3, pp. 380–394, May–June, 1998. This work was supported by RFFR grant No. 97-05-65534 and ISSEP grants No. 156p and a97-2633.     

On the "Rebound" Mechanism of Alkane Hydroxylation by Cytochrome P450: Electronic Structure of the Intermediate and the Electron Transfer Character in the Rebound Step

Two electromeric forms, a and b (a is the ground state in a solvent) exist for the hydroxo-iron complex 1, an intermediate in the rebound mechanism of alkane hydroxylation by cytochrome P450. Results of density functional and model solvent calculations of various species are in agreement with experimental findings, and imply the role of 1 a in the rebound mechanism.     

Stable σ-adducts of 4,6-dinitrotetrazolo[1,5-a]pyridine with alkoxide anions

The reaction of 2-chloro-3,5-dinitropyridine with two equivalents of KN₃ in the presence of ROH results in stable Meisenheimer-type -adducts of 4,6-dinitrotetra-zolo[1,5-a]pyridine with RO^– anions (R = H, Alk, Ph). The mechanism of -complex formation was suggested. The structure of the -adduct with R = Me was established by IR and NMR spectroscopy and by X-ray diffraction analysis.For the preliminary communication, see Ref. 1.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1278–1283, July, 1994.This work was supported by the Russian Foundation for Basic Research (project code 93-03-5329).     

Evaluation of the limits of maximal means

It is proved that the limit $$\mathop {\lim }\limits_{\Delta \to \infty } \mathop {\sup }\limits_\gamma \tfrac{1}{\Delta }\int_0^\Delta {f(\gamma (t))dt} $$ , wheref: ? → ? is a locally integrable (in the sense of Lebesgue) function with zero mean and the supremum is taken over all solutions of the generalized differential equation γ ∈ [ω1, ω2], coincides with the limit $$\mathop {\lim }\limits_{T \to \infty } \mathop {\sup }\limits_{c \geqslant 0} \varphi _f (k,{\mathbf{ }}T,{\mathbf{ }}c)$$ , where $$\varphi _f = \frac{{(k - 1)\bar I_f (T,c)}}{{1 + (k - 1)\bar \lambda _f (T,c)}},k = \frac{{\omega _2 }}{{\omega _1 }}$$ . Here ¯λf = λf /T, ¯ I_f =If/T, and λf is the Lebesgue measure of the set $$\{ \gamma \in [\gamma _0 ,\gamma _0 + T]:f(\gamma ) \geqslant c\} = A_f ,I_f = \int_{A_f } {f(\gamma )d\gamma } $$ . It is established that this limit always exists for almost-periodic functionsf.     

Contribution of dimensional factor to the potential of copper-containing electron-ion exchangers

The average size of copper particles in copper-containing electron-ion exchangers is determined with the aid of microscopy and x-ray diffractometry. The results are used to calculate the contribution made by a dimensional factor to the electrode potential. Compared to the potential of compact copper, the potential shift in the negative direction measured experimentally falls within the region of calculated values. The average size of copper particles remains practically unchanged after contact with a copper sulfate solution, testifying to stabilization of an ultradisperse state of copper particles by a polymer matrix.