Stochastic model of dissociation-recombination kinetics in micelles

The small number of reagents solubilized in a micelle prohibits the use of conventional reaction kinetics. In order to describe the kinetics of the reaction A + B ? AB proceeding in a micellar phase, a stochastic model is evaluated. The deviation of these results from those obtained by conventional kinetics may be as high as 20%.     

The magnetizability of excited-state hydrogen: temperature-independent paramagnetism in the B1Σ+u state

Components, of the magnetizability tensor for the B¹Σ⁺_u and a ³Σ⁺_g states ot the hydrogen molecule have been calculated for fixed bond lengths near equilibrium. Explicitly correlated “generalised James-Coolidge” type wavefunctions were used. It is found thilt in the B 1Σ⁺_u state the molecular magnetizability is a positive quantity.     

Examination of Contemporary Lake Sediments by Means of Thermal Analysis: The Dabie lake near Szczecin

An attempt was made to use thermal analysis (DTA, TG, DTG) for identification of the mineralogical composition of contemporary lake sediments. Sediments were investigated both in the natural state and after ignition at 300°C. Selected fractions of the sediments in the natural state were also studied. The thermoanalytical curves of mollusca shells, reed and plankton were also recorded for use in the interpretation of the thermoanalytical curves of sediments.This revised version was published online in November 2005 with corrections to the Cover Date.     

Different properties of exciplexes and excited states of CT complexes in the solid phase

The fluorescence, excitation and absorption spectra and fluorescence decay kinetics of charge-transfer (CT) complexes and exciplexes ofheteroaromatic cations and some other electron acceptors were investigated in ethanol at 77 K. Experimental data indicate that the fluorescence state of the exciplex may differ from that of the CT complex.     

Racemization of sulfinic esters with trichloroacetic anhydride

Both alkane- and arene-sulfinates undergo racemization and oxygen exchange reaction with trich-loroacetic anhydride. The rate of racemization of (?)menthyl (?)p-toluenesulfinate was found to be twice that of oxygen exchange, suggesting the reaction involves a Walden inversion. When reaction was carried out in benzene, the rate of racemization was found to be first order with respect to both sulfinic ester and trichloroacetic anhydride. The substituent effect is large (p = ?1.53) suggesting that the initial acylation is the rate-determining step. The rate of racemization was found to be retarded by the addition of perhaloacetic acid while very small catalytic effect of mercuric chloride was observed.     

The effect of the gas atmosphere on the phase transformation in the solid solution of MoO3 in V2O5

The nature of the structure transformation occurring under the influence of oxidizing or reducing gas atmosphere in powdered oxide (V₂O₅)_0.93 (MoO₃)_0.07 has been investigated. The formation of an intermediate compound in the inner parts of the catalyst grains during the oxidation and in the subsurface layers during the reduction has been observed.     

210Po in popular medicinal herbs from Poland

Herbs are an important part of traditional medicine in Poland. Therefore, the aim of this study was the determination of polonium ²¹⁰Po in 48 selected medicinal herb samples from the Polish market. The activity concentrations of ²¹⁰Po were measured using alpha spectrometry. The activity concentration of ²¹⁰Po was in the range from 0.3?±?0.1 to 28.2?±?0.4 Bq kg^–1. The obtained results were compared with corresponding studies conducted worldwide. A higher ²¹⁰Po activity concentration was observed in the above-ground part of plants. The obtained results show that the highest ²¹⁰Po activity concentration was observed in evergreen plants and winter-hardy plants. Yet even infusions with 2 g of the most contaminated herbs examined were considered to be radiologically safe.     

High-pressure (2+2)cycloaddition of toluene-4-sulphonyl isocyanate to glycals

High-pressure (2+2)cycloaddition of toluene-4-sulphonyl isocyanate to glycals is examined. Reactions proceed regiospecifically to afford single products in case of all 3-substituted glycals. Upon heating or even after standing at room temperature adducts undergo retro-addition to give starting glycals. Various aspects of the cycloaddition are discussed, especially ret-ro-reaction and rearrangement of β-lactams to α,β-unsaturated amides.     

Rotational isomerism in 1,4-disilabutane

Raman spectra of 1,4-disilabutane (DSB) are recorded in both liquid and solid states. IR spectra in the gas and solid phases are also recorded. Two rotational isomers, trans and gauche, are present in the gas and pure liquid phases. An assignment of the main features of the IR and Raman spectra is made, with the aid of normal coordinate calculations for the two isomers. The temperature dependence of the Raman spectrum of DSB is studied in the range 77–300 K. The enthalpy difference between the two isomers is 5.01 ± 0.31 kJ mol^?1. This value is expected to be higher for gaseous DSB.