Esterification of n-Butanol with Acetic Acid in the Presence of Heteropoly Acids with Different Structures and Compositions

The esterification reaction of n-butanol with acetic acid ([BuOH] : [HOAc] = 1 : 15 mol/mol; 55°C, 5% H₂O) was studied in the presence of tungsten heteropoly acids of the Keggin (H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, H₅PW₁₁TiO₄₀, H₅PW₁₁ZrO₄₀, and H₃PW₁₁ThO₃₉) and Dawson structure (-H₆P₂W₁₈O₆₂, H₆P₂W₂₁O₇₁(H₂O)₃, H₆As₂W₂₁O₆₉(H₂O), and H₂₁B₃W₃₉O₁₃₂). The reaction orders with respect to H₆P₂W₂₁O₇₁(H₂O)₃, H₃PW₁₂O₄₀, and H₆P₂W₁₈O₆₉are equal to 0.78, 1.00, and 0.97, respectively. It was found that the reaction rate depends on the acidity, as well as on the structure and composition of heteropoly acids. The H₂₁B₃W₃₉O₁₃₂heteropoly acid is most active, whereas the Keggin-structure heteropoly acids exhibit the lowest activities. Of the Keggin structure heteropoly acids, H₅PW₁₁ZrO₄₀exhibits the highest activity because of the presence of a Lewis acid site in its structure.     

Heterocyclization of Derivatives of 4-Oxoalkanoic Acids to 1,5-Disubstituted Pyrrolin-2-ones

Conditions were developed for the synthesis and production of 1-aryl-5-alkyl(aryl)-3H- and 1-aryl-5-alkyl(aryl)-5H-pyrrolin-2-ones from the amides and esters of 4-oxoalkanoic acids. It was established that the yield and ratio of the 3H and 5H isomers depend on the substrate employed in the reaction.     

Alkylation of p-substituted phenols by heteropoly acids

Liquid-phase alkylation of p-tert-butylphenol (TBP) and p-cresol by olefins and benzyl chloride in the presence of solid heteropoly acids (HPA) H₃PW₁₂O₄₀ and 25% H₃PW₁₂O₄₀/SiO₂ at 100–150°C provides high yields of mono- and disubstituted products. HPAs are more active than H₂SO₄, easily separated from the reaction mixture and can be used repeatedly. -- () - () H₃PW₁₂O₄₀ 25% H₃PW₁₂O₄₀/SiO₂ 100–150°C - - . , H₂SO₄, - - .     

Michael condensation of 3-arylidene-3H-pyrrol-2-ones and 3-arylidene-3H-furan-2-ones with cyclohexanone

The Michael condensation in the series of 5-aryl-3-arylidene-3H-pyrrol-2-ones and 5-aryl-3-arylidene-3H-furan-2-ones, containing an activated C=C bond, with cyclohexanone was investigated. It was shown that the condensation products were 1,5-dicarbonyl compounds containing a heterocyclic fragment. The enolization of one of the oxo groups, leading to the formation of hydroxypyrrole or hydroxyfuran structures, was demonstrated by the spectral data. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 6, pp. 823–827, June, 2007.     

Thermoelastic martensitic transformations in single crystals with disperse particles

The results of investigations into the influence of disperse particles on the temperatures of martensitic transformations as well as values of thermal and mechanical hysteresis in the FeNiCoAlTa, CoNiGa, NiFeGa, TiNi single crystals are reported. It is shown that the disperse particles are responsible for refining martensitic crystals and changing their fine twin structure as compared with the monophase state. This, in turn, affects the values of thermal and mechanical hysteresis and the temperature range of superelasticity.     

Polymers based on ionic monomers with side phosphonate groups

A number of new ionic vinyl monomers composed of 1-vinylimidazolium cation with diethoxy- and dihydroxyphosphoryl groups and various anions—Br^?, (CN)₂N^?, and (CF₃SO₂)₂N^?—are synthesized. The free-radical polymerization of the monomers in solutions of molecular and ionic solvents yields new polymer analogs of ionic liquids, and their molecular-mass characteristics, solubility, heat resistance, thermal stability, and electrical conductivity are estimated. It is shown that the incorporation of bulky phosphorylalkyl side substituents into the vinylimidazolium polycation causes a decrease in the glass-transition temperature and an increase in the ionic conductivity of polymer salts. The highest ionic conductivity (2.6 × 10^?5 S/cm at 25°C) is exhibited by the polymer with the (CN)₂N^? anion.     

Monohalogenated ferrocenes C5H5FeC5H4X (X = Cl,Br and I) and a second polymorph of C5H5FeC5H4I

The structures of the three title monosubstituted ferrocenes, namely 1‐chloroferrocene, [Fe(C₅H₅)(C₅H₄Cl)], (I), 1‐bromoferrocene, [Fe(C₅H₅)(C₅H₄Br)], (II), and 1‐iodoferrocene, [Fe(C₅H₅)(C₅H₄I)], (III), were determined at 100 K. The chloro‐ and bromoferrocenes are isomorphous crystals. The new triclinic polymorph [space group P, Z = 4, T = 100 K, V = 943.8 (4) ų] of iodoferrocene, (III), and the previously reported monoclinic polymorph of (III) [Laus, Wurst & Schottenberger (2005). Z. Kristallogr. New Cryst. Struct. 220 , 229–230; space group Pc, Z = 4, T = 100 K, V = 924.9 ų] were obtained by crystallization from ethanolic solutions at 253 and 303 K, respectively. All four phases contain two independent molecules in the unit cell. The relative orientations of the cyclopentadienyl (Cp) rings are eclipsed and staggered in the independent molecules of (I) and (II), while (III) demonstrates only an eclipsed conformation. The triclinic and monoclinic polymorphs of (III) contain nonbonded intermolecular I...I contacts, causing different packing modes. In the triclinic form of (III), the molecules are arranged in zigzag tetramers, while in the monoclinic form the molecules are arranged in zigzag chains along the a axis. Crystallographic data for (III), along with the computed lattice energies of the two polymorphs, suggest that the monoclinic form is more stable.     

Power and lasing threshold for longitudinally pumped lasers with intracavity raman self-conversion

A method is developed for calculating the power and lasing threshold for longitudinally pumped lasers with intracavity Raman conversion. The theoretical analysis is based on equations for the powers of light beams in the cavity. Expressions for the power and lasing threshold of a Raman laser with self-conversion as functions of the parameters of the active medium, cavity, and pumping, taking into account the overlap of all the interacting beams, are derived and analyzed.     

Morphology of hybrid polystyrene-block-poly(ethylene oxide) micelles: analytical ultracentrifugation and SANS studies

Morphology and structure of aqueous block copolymer solutions based on polystyrene-block-poly(ethylene oxide) (PS-b-PEO) of two different compositions, a cationic surfactant, cetyl pyridinium chloride (CPC), and either platinic acid (H2PtCl6.6H2O) or Pt nanoparticles were studied using a combination of analytical ultracentrifugation (AUC), transmission electron microscopy (TEM), and small angle neutron scattering (SANS). These studies combining methods contributing supplemental and analogous structural information allowed us to comprehensively characterize the complex hybrid systems and to discover an isotope effect when H2O was replaced with D2O. In particular, TEM shows formation of both micelles and larger aggregates after incorporation of platinic acid, yet the amount of aggregates depends on the H2PtCl6.6H2O concentration. AUC reveals the presence of micelles and micellar clusters in the PS-b-PEO block copolymers solution and even larger (supermicellar) aggregates in hybrids (with CPC). Conversely, SANS applied to D2O solutions of the similar species indicates that micelles are spherical and no other micellar species are found in block copolymer solutions. To reconcile the SANS and AUC data, we carried out AUC examination of the corresponding D2O block copolymer solutions. These measurements demonstrate a pronounced isotope effect on micelle aggregation and micelle size, i.e., no micelle aggregation in D2O solutions, revealing good agreement of AUC and SANS data.