Two new macrocyclic diaryl ether heptanoids from Boswellia ovalifoliolata

The stems of Boswellia ovalifoliolata BAL. & HENRY (Burseraceae) afforded two new macrocyclic diaryl ether heptanoids, ovalifoliolatin A (1) and B (2) together with three known compounds; acerogenin C (3), 3 alpha-hydroxyurs-12-ene (4), and sitost-4-en-3-one (5). The structures were established by means of spectroscopic analysis and compounds 1, 3-5 were evaluated for their antibacterial activity.     

Electroinitiated cationic polymerization of styrene in the presence of ferric chloride

The electroinitiated polymerization of styrene has been studied in acetone with ferric chloride as the electrolyte. At a fixed monomer concentration, the polymer yield depends on the current strength as well as the concentration of ferric chloride. The molecular weight of the polymer lies in the range of 1000–3000. Addition of zinc chloride to the system or replacement of the solvent by DMF (partly or fully) or methanol retards the polymerization. The current exponent of polymerization is unity with a reaction rate constant of 4.416 × 10^?2 reaction percent per hour. The locus of polymerization is the anode compartment. A cationic mechanism has been proposed for the polymerization, the initiating step consisting of an electron transfer from an adsorbed charge transfer complex of styrene and ferric chloride.     

Approximate Queueing Formulae Based on Consideration of the Busy Period

An approximation formula to one in M/M/1 queueing theory for hours in a queue is examined. Then it is extended to models M/D/1 and M/E _k /1 whereby wasted time or queue length is found to lie between two extremes. An empirical approximation to traffic intensity called utilization rate is used.     

Kinetics of oxidation of Indigo Carmine by potassium peroxydisulfate

The reaction is first order in potassium peroxydisulfate and zero order in Indigo Carmine. Hydrogen ions have no effect on the rate in the acidity range of 0.0–0.2 M. Allyl acetate inhibits the reaction. A radical chain mechanism is proposed.

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. 0 0,2 M . . .

     

Novel analogues of ascomycin with modifications in the amino acid unit through photochemistry: the synthesis of 5,6-dehydroascomycin, SDZ ASQ 871

Irradiation of ascomycin 1a and its derivatives in MeOH, EtOH and propanol resulted in alkoxylation of the pipecolic acid moiety in the ε-position with concomitant reduction in the tricarbonyl region leading to 6-alkoxy-9-hydroxy derivatives in high stereoselectivities and good yields. The products, after reoxidation of the C(9)-OH, afforded the 6-alkoxy analogues of the parent compounds. Elimination of MeOH from the photoproducts, followed by oxidation gave the corresponding 5,6-dehydro amino acid analogues. Similarly, starting from the proline analogue 7 modifications in the pyrrolidine moiety could be achieved.     

Surfactant immobilized interlayer species bonded to montmorillonite as recyclable adsorbent for lead ions

Removal of lead ( Pb2+ ) ions from aqueous solution by adsorption onto surfactant-immobilized interlayer species bonded to montmorillonite clay (SIIS-clay) was investigated. Surfactant-immobilized interlayer chromate bound to clay (SIICr-clay) was prepared by treatment of montmorillonite clay with hexadecyltrimethylammonium (HDTMA) bromide followed by chromate adsorption at the intergallery framework of the clay. Experiments were carried out as a function of solution pH, solute concentration, and temperature (5-45 degrees C). The Dubinin-Kaganer-Radushkevich (DKR) model was adopted to describe the single-solute adsorption isotherms. Adsorption energy for lead ions on SIICr-clay computed from the DKR equation shows that a precipitation mechanism was operative. The thermodynamic parameters ( Delta G 0, Delta H 0, and Delta S 0) for lead ion adsorption on SIICr-clay were also determined from the temperature dependence. The kinetics of metal ion adsorption was examined and the first-order rate constant was finally evaluated. Adsorbed lead ions could be recovered completely on leaching with the disodium salt of ethylenediamine tetraacetic acid (EDTA) solution and the adsorbent was found to readsorb lead ions repeatedly after leaching. Thus, surfactant-modified smectite clays offer an effective method for designing a recyclable adsorbent for lead ions.     

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