Thermodynamics of mixtures of poly(tetramethylene oxide)s and 1, 4-dioxane

Vapor pressures and densities of solutions of poly(tetramethylene oxide) fractions (molecular weights 650, 1000, and 2000) in 1, 4-dioxane have been determined at 30 and 40°C. The data have been utilized to determine the activities and thermodynamic functions of dilution. Excess volumes have been determined from the density data. Flory's equation of state theory quantitatively predicts the reduced residual functions X, X_h, and X_s. Predicted as well as experimental values of X_s are found to be negative. The theory predicts correctly the sign of the excess volume but quantitative agreement between theory and experiment is not obtained.     

Lewis acid mediated thienium cation diels-alder reaction: A new method for regio- and stereoselective functionalization of 1,3-dienes

Under the influence of aluminum chloride the β-ethylthionitroolefin results in the formation of the thienium cation, which reacts with a variety of 1,3-dienes in the Diels-Alder sense. The cleavage of the resulting ring provides in one pot the 1,4-functionalized olefins in regio- and stereoselective manner.     

Quotient-bounded elements in locally convex algebras. II

Consideration of quotient-bounded elements in a locally convexGB ^*-algebra leads to the study of properGB ^*-algebras viz those that admit nontrivial quotient-bounded elements. The construction and structure of such algebras are discussed. A representation theorem for a properGB ^*-algebra representing it as an algebra of unbounded Hilbert space operators is obtained in a form that unifies the well-known Gelfand-Naimark representation theorem forC ^*-algebra and two other representation theorems forb ^*-algebras (also calledlmc ^*-algebras), one representinga b ^*-algebra as an algebra of quotient bounded operators and the other as a weakly unbounded operator algebra. A number of examples are discussed to illustrate quotient-bounded operators. An algebra of unbounded operators constructed out of noncommutativeL ^p-spaces on a regular probability gauge space and the convolution algebra of periodic distributions are analyzed in detail; whereas unbounded Hilbert algebras andL ^w-integral of a measurable field ofC ^*-algebras are discussed briefly.     

Photoinitiated reactions of (η-C5H5)2MH3 (M  Nb,Ta) with Mn2(CO)10: structure of (η-C5H5)2(CO)Ta(μ-H)Mn2(CO)9

The photoreaction of (η-C₅H₅)₂TaH₃ with Mn₂(CO)₁₀ gives, inter alia, (η-C₅H₅)₂(CO)Ta(μ-H)Mn₂(CO)₉, whose crystal structure reveals an open, bent trimetallic framework. Preliminary mechanistic studies show that this and the analogous niobium reaction proceed via a complex sequence of thermal steps following photoinitiation.     

Electrochemical studies of copper(II) 2-acetylpyridine4 N-dialkylthiosemicarbazones. Relation to their spectral,magnetic, and biological properties

Summary Quasireversible copper(II)/copper(I) couples are observed for [Cu(L)X], where X=Cl or Br, and L=an anion of a 2-acetylpyridine⁴ N-dialkylthiosemicarbazone. Irreversible reduction potentials of the tridentate (NNS) ligands increase as the size of the⁴ N-dialkyl-substituent increases. The growth inhibitory activity of the complex againstPaecilomyces variotii (but not other fungi tested) also decreases with increasing ligand size, suggesting that ease of ligand reduction is a significant factor in activity against this fungus.     

Studies on some radical transfer reactions. Part I. Hydrogen atom abstraction from some organic substrates by ȮH radicals

Polymerization of methyl methacrylate was carried out in aqueous and nonaqueous media in the presence of some sulfonated and carboxylic organic compounds, hydroxyl radicals generated from hydrogen peroxide being used as initiators of polymerization. The occurrence of radical transfer reactions by way of hydrogen atom abstraction from the organic substrates by the ?H radicals was demonstrated by the detection of sulfonate and carboxyl endgroups in the respective polymers. It was found that the radical transfer reactions were more favored in aqueous media than in nonaqueous systems.     

Diastereoselective amidoalkylation of (3S,7aR)-6-benzyl-7-hydroxy-3-phenyltetra- hydro-5H-imidazo[1,5-c][1,3]thiazol-5-one: a short and highly efficient synthesis of (+)-biotin

A short and highly efficient synthesis of (+)-biotin in 10 steps with 20% overall yield has been achieved from L-cysteine involving amidoalkylation of hydroxy imidazothiazolone 4 via an acyliminium ion intermediate to furnish C-7-substituted imidazothiazolones 5b as the key step.     

Total synthesis of (+)-blastmycinone and formal synthesis of (+)-antimycin A3b

The formal synthesis of (+)-antimycin A_3b and the total synthesis of (+)-blastmycinone were achieved using, as a key step, a method developed by us for the synthesis of 2-methyl-1,3-diols via Ti(III)-mediated diastereo- and regioselective opening of trisubstituted 2,3-epoxy alcohols, to carry out the stereoselective construction of the hydroxy-acid segment. An interesting intramolecular radical translocation took place during the epoxide opening process transforming its vicinal PMB-ether in situ, into an ‘1,2-O-(p-methoxy)benzylidene’ ring.     

A constitutional diagram of the system TiC−HfC−“MoC”

The system TiC–HfC–MoC was investigated by means of melting point, differentiothermoanalytical, X-ray diffraction and metallographic techniques on hotpressed as well as melted alloy specimens. A constitutional diagram from 1500°C through the melting range was established.Investigation of the (Hf, Mo)C system (isopleth: HfC_0.98–MoC_1.0) showed a small miscibility gap within the cubic monocarbide solution () [Tc=1630°C, (HfC)_0.45(MoC)_0.55]. The miscibility gap interacts with the solvus curve with a monotectoid-like decomposition reaction at 1575°C, (HfC)_0.35(MoC)_0.65.At temperatures below 1630°C, phase equilibria within TiC–HfC–MoC are characterized by a large miscibility gap connecting the TiC–HfC and HfC–MoC boundary systems. Additions of MoC to TiC–HfC alloys decrease the critical temperature (1780°C); additions of TiC to HfC–MoC alloys raise the critical temperature (1630°C). No maximum type ternary critical point or saddle point was found to occur.Isothermal sections were prepared at 1500°C and 1650°C. At temperatures above 1960°C (-MoC+C-MoC) a complete solid solution (-B 1) is formed within TiC–HfC–MoC. The melting behaviour (liquidus projection of TiC–HfC–MoC) shows flat melting temperatures in the MoC corner but extremely heterogeneous melting near the TiC–HfC boundary.Isothermal sections have been calculated assuming regular solutions.With 5 Figures