Alternating copolymer of styrene–acrylonitrile obtained with vanadium-based complex catalyst in presence of monomers

Vanadium-based catalyst complexes prepared in the presence of monomers have been used for the copolymerization of styrene and acrylonitrile. VOCl₃–Al(i-C₄H₉)₃ catalyst system seems to yield an alternating copolymer. The copolymers are easily soluble in DMF and have low softening points.     

Chemoselective hydrogenation of substituted nitroaromatics using novel water-soluble iron complex catalysts

Chemoselective hydrogenation of substituted nitroaromatic compounds by water-soluble iron complex catalysts with molecular hydrogen has been reported for the first time. This biphasic catalyst presents an opportunity for a solvent-free hydrogenation. This catalyst system provides a low-cost, efficient alternative to the selective but environmentally unacceptable stoichiometric reductions as well as the supported noble metal catalysts used for hydrogenation. An efficient recycling strategy has resulted in a cumulative turnover number above 6000.     

Polymerization of styrene with chromium acetylacetonate–triisobutylaluminum catalyst system

Styrene is polymerized with chromium acetylacetonate–triisobutylaluminum catalyst at 40°C in a benzene medium. At the stoichiometric ratio of Al/Cr of 4, the activity for polymerization was found to be maximum. Further, the kinetic studies were carried out at this ratio of Al/Cr of maximum activity. The kinetics of polymerization and the total activation energy around 10.00 kcal/mole suggest a coordinate anionic mechanism.     

Stereoselectivity ratios in a simple Diels-Alder reaction in aqueous salt solutions of alcohols

This is the first exhaustive report on the variation of stereoselectivity ratios for a simple Diels-Alder reaction between cyclopentadiene and methyl acrylate. The reaction was carried out in aqueous mixtures of methanol, ethanol, propan-1-ol and butan-1-ol in presence of LiClO₄, LiCl, NaCl, KCl, CaCl₂ and MgCl₂. The endo stereoisomer decreases with the increase in carbon chain length of the alcohol. However, LiClO₄, a salting-in agent in water becomes salting-out in aqueous mixtures of alcohols. The solvent properties, thus can be attuned by adjusting the amount of solvents and salts.     

LIGHT INDUCED INTERACTION BETWEEN RHODOPSIN AND GTP DEPENDENT PROCESSES IN ROD OUTER SEGMENTS—I. KINETIC ANALYSES OF LIGHT SCATTERING TRANSIENTS

Abstract— A fast light-induced light scattering transient in the presence of Mg²⁺ and GTP is observed from bovine rod outer segment suspension. This transient is studied at various temperatures, degrees of photo-bleaching and GTP concentration. The kinetic analysis of this signal at low photo-bleaching (∼ 5%) reveals two different processes which are consecutive rather than simultaneous. The rate of both processes depends upon the extent of photo-bleaching and indicates that each process requires a photolyzed rhodopsin intermediate. At low temperature, the rate constant of both the processes increases with the extent of photo-bleaching while at higher temperatures it decreases. The calculated activation energy of both processes decreases with increasing photo-bleaching. It has also been observed that with decreasing GTP concentration, the rates of both processes decrease indicating that the two processes though first order are most likely bimolecular, first order in both GTP and the photolytic rhodopsin intermediate (metarhodopsin II)     

Radiation-induced copolymerization of hydrophilic monomers with vinyl acetate: Synthesis and thermal properties

Radiation-induced copolymerization of hydrophili+ monomers, viz., 2-hydroxyethyl methacrylate (HEMA), 2-hydroxypropyl methacrylate (HPMA), and N-vinyl-2-pyrrolidone (NVP) with vinyl acetate (VAc) was carried out in bulk at 25°C. The copolymer composition was determined from the acetoxy content. The copolymerization parameters were determined by a graphical method and compared with those determined by the Yezrielev, Brokhina, and Roskin (YBR) method. Thermal properties of copolymers were studied by GC-MS. Probable mechanisms were suggested from the products obtained.     

Simultaneous Determination of Enalapril and Losartan in Pharmaceutical Preparations by UV Spectrophotometry and LC

The simultaneous determination of enalapril (Ena) and losartan (Los) in solid dosage forms were done by two methods. The first method involves spectrophotometric determination using the simultaneous equation method at 222 and 250 nm for Ena and Los, respectively. The second method involved an RP-LC method of analysis using methanol:water:acetonitrile (45:35:20% v/v) as the mobile phase. Both methods were satisfactorily validated as per ICH guidelines.     

Long range forces and limits on unparticle interactions

Couplings between standard model particles and unparticles from a nontrivial scale invariant sector can lead to long range forces. If the forces couple to quantities such as baryon or lepton (electron) number, stringent limits result from tests of the gravitational inverse square law. These limits are much stronger than from collider phenomenology and astrophysics.