The synthesis of 1,2-diacetyl- and 1,2-diethylferrocenes

A method is described for the preparation of 1,2-diacetylferrocene, in which ferrocene is acetylated with acetyl chloride in the presence of AlCl₃ in methylene chloride. Addition of the ferrocene to an excess of the acetylation mixture over a prolonged period was found to be most favourable. The 1,2-diacetylferrocene formed proved to be free of the 1,3-isomer. It was reduced with LiAlH₄/AlCl₃ to 1,2-diethylferrocene.     

The rates of the exchange reactions between [Gd(DTPA)]2- and the endogenous ions Cu2+ and Zn2+: a kinetic model for the prediction of the in vivo stability of [Gd(DTPA)]2-, used as a contrast agent in magnetic resonance imaging

The kinetic stability of the complex [Gd(DTPA)]2- (H5DTPA = diethylenetriamine-N,N,N',N",N"-pentaacetic acid), used as a contrast-enhancing agent in magnetic resonance imaging (MRI), is characterised by the rates of the exchange reactions that take place with the endogenous ions Cu2+ and Zn2+. The reactions predominantly occur through the direct attack of Cu2+ and Zn2+ on the complex (rate constants are 0.93+/-0.17 M(-1) s(-1) and (5.6+/-0.4) x 10(-2)M(-1) S(-1), respectively). The proton-assisted dissociation of [Gd(DTPA)]2- is relatively slow (k1 = 0.58+/-0.22 M(-1) s(-1)), and under physiological conditions the release of Gd3+ predominantly occurs through the reactions of the complex with the Cu2+ and Zn2+ ions. To interpret the rate data, the rate-controlling role of a dinuclear intermediate was assumed in which a glycinate fragment of DTPA is coordinated to Cu2+ or Zn2+. In the exchange reactions between [Gd-(DTPA)]2- and Eu3+, smaller amounts of Cu2+ and Zn2+ and their complexes with the amino acids glycine and cysteine have a catalytic effect. In a model of the fate of the complex in the body fluids, the excretion and the "dissociation" of [Gd(DTPA)]2- are regarded as parallel first-order processes, and by 10 h after the intravenous administration the ratio of the amounts of "dissociated" and excreted [Gd(DTPA)]2- is constant. From about this time, 1.71% of the injected dose of [Gd(DTPA)]2- is "dissociated". The results of equilibrium calculations indicate that the Gd3+ released from the complex is in the form of Gd3+-citrate.     

Standard enthalpy and heat capacity of solid tin telluride

The published data on the heat capacity of tin telluride were analyzed. The C _p values were demonstrated to be consistent only at temperatures below 56 K. Some data on the heat capacity of SnTe within 80–453 K were found to differ significantly. The heat capacity C _p was measured on a DSM-2M calorimeter within a temperature range of 350–600 K and other thermodynamic functions of tin telluride were calculated.     

Reduction of nitrates,the no donors,by hemoglobin in the presence of cysteine

Hemoglobin (Hb) reduces 3,3-bis(nitroxymethyl)oxetane (NMO) only in the presence of cysteine (Cys) via intermediate cysteine thionitrate. The kinetics of the reaction of NMO with Cys and the kinetics and mechanism of formation of NO in the ternary system Hb-NMO-Cys were studied. The formation rate of Hb-NO in the ternary system is higher than that of Hb-NO in the reaction of Hb only with NO ₂ ⁻ generated in the binary system NMO-Cys. The second-order rate constants of the main reaction steps in the system Hb-NMO-Cys were estimated by simulating the kinetics of the reactions with a system of equations taking into account equilibria between all components of the reaction mixture. Hemoglobin reduces cysteine thionitrate, the intermediate in the reaction of NMO with Cys, to NO. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 4, pp. 725–731, April, 2007.     

The Rotational Spectrum of SiHF3 in the Vibrational State υ6=2: Observation of Direct l-Type Resonance Transitions

The υ₆=2 vibrational state of the main isotopomer of trifluorosilane, ²⁸SiHF₃, has been investigated in the centimeter- and millimeter-wave ranges. Rotational spectra following the Δ J=1, Δk=Δ l=0 selection rule have been measured up to J=24 and K=23 and for both values of ∣l∣. Two types of direct l-type resonance transitions induced by the (Δ l=Δk=±2) interaction could be observed by means of waveguide Fourier transform microwave spectroscopy in the range 8-26 GHz: 252 transitions following the Δ J=0, Δl=Δk=±2 selection rule covering values of J=7-39 and G=∣k-l∣ from 1 to 18 and 90 transitions following the Δ J=0, Δl=Δ k=±4 selection rule covering values of J=17-52 and G from 1 to 4. Due to the strong (2,2) resonance, 18 A₁-A₂ splittings of the k=l=±2 states from J=36-53 could also be observed. Accidental near-degeneracies lead to strong perturbations due to Δ (k-l)=±3 interactions, enabling the observation of perturbation-allowed transitions with selection rules k=±3(l=±2)↔±4(±2), ±2(±2), A₊↔ ±1(?2), A₋ and ± 1(0)↔± 6(±2). In a multiple-fit analysis the experimental data have been refined using five reduced forms of the effective Hamiltonian as proposed by Sarka and Harder [J. Mol. Spectrosc.197, 254-261 (1999)]. Parameters up to seventh order have been determined including the axial rotational constant C for both values of ∣l∣ and the vibrational separation of the ∣l∣=0 and 2 states. The unitary equivalence of the determined parameter sets has been demonstrated up to fifth order. Differences of the rotational constants in the various parameter sets have been explained by the theory of reduction. Sign relations of the fitted parameters and general features of the direct l-type resonance spectrum in a υ_t=2 level are discussed.     

Plexin B3 promotes neurite outgrowth,interacts homophilically,and interacts with Rin

Background  

Plexins, known to date as receptors of semaphorins, are implicated in semaphorin-mediated axon repulsion and growth cone collapse. However, subtype-specific functions of the majority of the nine members of the mammalian plexin family are largely unknown. In order to investigate functional properties of B-plexins, we analyzed the expression of human and murine plexin B3 and expressed full-length human plexins B2 (B2) and B3 (B3) in NIH-3T3 cells.     

Solubility polytherm and the influence of temperature on the enthalpy and entropy of dissolution

The significance and metrological meaning of parameters accessible to regressive estimates from the experimental data on solubility polytherms are refined using corollaries to the universal interrelation between the Gibbs energy, enthalpy, and entropy of dissolution. A standard procedure for processing solubility polytherms is suggested. Its informativeness is illustrated for the example of new metrologically verified data on the polytherm of solubility of ferrocene in pure water.     

Synthesis of β-carbonylphosphine oxides and phenyl-substituted ethylenediphosphine oxides. study of their complexing with alkali metals cations

The synthesis of some β-carbonylphosphine oxides and phenyl-substituted ethylenediphosphine oxides was carried out. Their complexing with alkali metals cations was studied. Compounds obtained were shown to possess clearly expressed Li/Na selectivity.     

Perfluoropropylene oxide as a reagent for the synthesis of germanium,titanium, tin,and zirconium fluorides

A new method of preparation of germanium, titanium, tin, and zirconium fluoride alcohol complexes by reaction of the metal oxides with a solution of perfluoropropylene oxide in methanol is developed. The reaction of the complexes obtained with ligands (L = 1,10-phenanthroline or dimethyl sulfoxide) was studied, and the structure of the obtained compounds was determined. A new route to the synthesis of 1-fluorogermatrane is developed.