Radical polymerization of styrene initiated by styrene–arsenic sulfide complex

Styrene forms a complex with arsenic sulfide which in DMF at 85°C initiates radical polymerization yielding high molecular weight polymer. The order of reaction, with respect to initiator and monomer, is 0.5 ± 0.02 and unity, respectively. The energy of activation for the system computed as 96 kJ mol^?1 and the polymerization is retarded by hydroquinone. A possible mechanism for reaction has also been proposed.     

Studies on some newer polyhydrazides containing amide linkages. III

Novel polyhydrazides having inherent viscosities in the range of 0.24–0.38 dL g^?1 were prepared by polymerizing a series of hydrazides with different diacid chlorides in polar aprotic solvents. These polymers display a wide range of solubility in a number of solvents. They start decomposing at about 200°C in air. Results of differential thermal and thermogravimetric analysis show that a steep weight loss takes place mainly in the range of 300–440°C.     

Dynamic light-scattering analysis of the electrostatic interaction of hexahistidine-tagged cytochrome P450 enzyme with semiconductor quantum dots.

Currently, there is great interest in the development of methods suitable for determining the stoichiometry of biomolecules attached to nanoparticles. We describe the use of the dynamic light-scattering technique (DLS) to determine the stoichiometry of the protein cytochrome P450(BSbeta) attached to CdS and CdSe quantum dots (QDs). The enzyme-conjugated QDs have different diffusion characteristics compared to the QD and enzyme precursors, expressed in their size, scattering intensity as well as zeta-potential values. The significant enhancement of the scattering intensity of QDs observed upon conjugation with the P450(BSbeta) due to the refractive-index increment and the systematic variation in zeta potential resulting from charge neutralization of the anionic QDs by the cationic histidine-tagged P450(BSbeta) have been used for stoichiometry determination.     

Influence of the nature of organic diluents on the extraction of uranium(VI) by bis(2-ethylhexyl) sulfoxide from nitric acid solutions

The extraction of uranium(VI) from nitric acid solutions by bis(2-ethylhexyl) sulfoxide (BESO) has been examined using sixteen inert organic diluents in order to establish the correlation between its distribution coefficient and some physico-chemical properties of the diluents. The extracted solvated species is shown to be UO₂(NO₃)₂·2BESO, irrespective of their nature. The extraction rate is lower in halogen substituted hydrocarbons as compared to the other diluents used. Among benzene derivatives, extraction is found to decrease with number of substituted methyl groups. Extraction efficiency decreases as the organic solvent is varied in the order: benzene>nitromethane>toluene> >nitrobenzene>cyclohexane>p-xylene>monochlorobenzene>dodecane>o-dichlorobenzene> >hexane>decalin>1,2-dichloroethane>1,1,1-trichloroethane>carbon tetrachloride> >tetrachloroethane>chloroform. Among the properties showing good correlations with distribution coefficient are Hansen's three-dimensional solubility parameters and Dimroth's empirical solvent polarity parameters [E _T(30) ]. Polarizability indices are most satisfactorily applicable to a wide variety of solvents.     

A Concise, Enantioselective Synthesis of (-)- and (+)-Hongconin

Optically pure enone 9c, available in three steps from known 6-deoxy D-galactal derivative 7b, reacts with cyanophthalide 6 to directly afford the natural product (-)-hongconin (1), a compound from traditional Chinese medicine recently shown to exhibit antianginal activity. The enantiomer of 1 and its (+)-cis-diastereomer were also synthesized in a parallel fashion from the L-sugar counterpart. The use of C-glycoside Michael acceptors, as opposed to their O-glycoside counterparts, represents a potentially useful simplification of phthalide annulation methodology in synthesizing numerous other such optically pure isochromanquinoids, since it obviates the inconvenience of additional steps late in the synthetic scheme associated with reductive manipulation of a remaining acetal moiety into the desired pyran ring substituent.     

Determination of gallium in tumour-affected tissues by means of spectroscopic techniques

A comparative investigation was carried out on the suitability of atomic absorption spectrometry and of emission spectrography with arc and hollow-cathode excitation sources for determination of gallium (μg g^-1) in biological samples. The three methods give reliable results. Hollow-cathode emission spectrography was found to be influenced to a lesser extent by matrix effects and to be more precise than the other two techniques.