Structures of Addition Products of Acetylenedicarboxylic Acid Esters with Various Dinucleophiles. An application of C,H-spin-coupling constants

Heterocyclic compounds obtained by addition of acetylenedicarboxylic acid esters to thioureas, cyclic amidines and o-difunctionalized aromatic systems have been studied by ¹³C-NMR. In particular, C, H-spin-coupling constants over two and three bonds were used to differentiate between the various constitutional isomers and to establish the configuration of trisubstituted exocyclic C, C-double bonds. The configurational significance and diagnostic value of vicinal cis and trans C,H-spin coupling is again demonstrated in the present series.     

Synthesis,crystal structure and reactivity of trans-diaquo N,N′-ethylenebis-(3-methoxysalicylideneiminato)chromium(III)

A new chromium(III) Schiff base complex, [Cr(3-methoxysalen)(H₂O)₂]ClO₄, where salen=N,N-ethylenebis- (salicylideneimine), has been synthesized and characterized by spectroscopic techniques. Single crystal X-ray data reveals that the complex assumes a trans-diaquo structure with formulation [Cr(C₁₈H₂₂N₂O₆)]ClO₄ but, unlike in Cr (salen)(H₂O)₂ ⁺, the two trans-water molecules are equidistant from Cr^III. The effect of the substituent on the phenyl ring in respect of redox reactivity has been investigated. The kinetics of the oxidation of [Cr(Schiff base)- (H₂O)₂]ClO₄, where Schiff base=salen, (1) and 3-OMe-salen, (2) by PhOI has been studied. The bimolecular rate constant for the formation of the O=Cr^v Schiff base in case of (2) was four times faster than that of (1). The introduction of the OMe group substituent on the phenyl ring influences not only the structure and crystal packing, but also the reactivity of the complex and the electronic environment around the metal ion.     

Reversed-phase partition chromatographic separations with 2-ethylhexyl dihydrogen phosphate and di-2-ethylhexyl hydrogen phosphate

Di-2-ethylhexyl hydrogen phosphate (HDEHP) and 2-ethylhexyl dihydrogen phosphate (H(2)MEHP) are compared as stationary phases in reversed-phase chromatography of selected lanthanides, strontium, yttrium, barium, manganese(II), iron(III), cobalt(II), nickel, gold(III), platinum(IV), palladium(II) and silver. Chromatograms were mainly developed with hydrochloric acid at various concentrations. In general H(2)MEHP was found to be less satisfactory than HDEHP. Development of chromatograms by dilute aqueous electrolytes on paper is slower and separations of chemically similar metals such as lanthanides is not encouraging. However, movement of lanthanides by EDTA at pH 3 in an aqueous sodium perchlorate medium occurs only on H(2)MEHP-treated paper. Good separations of iron(III) and cobalt(II) are possible on paper treated with either ester, and gold(III) and platinum(IV) are separated on HDEHP-impregnated paper. Column methods for the separation of carrier-free gold-199 and iron-59 from macro-amounts of neutron-irradiated platinum and cobalt, respectively, have been developed.     

Blood protein purification and simultaneous removal of nonenveloped viruses using tangential-flow preparative electrophoresis

Gradiflow is new technology allowing purification of important blood proteins from viral contaminated plasma. Protein purification is based on unique scalable tangential-flow preparative electrophoresis, and is distinct from current technology because protein purification and virus removal are performed in the same step. This one-step removal and purification exploits both the size and charge of target proteins. The medically important blood proteins, immunoglobulin G (IgG) and alpha-1-antitrypsin, were chosen to demonstrate the ability of this process to purify proteins from contaminated plasma. Clearance factors achieved by infectivity assays and polymerase chain reaction (PCR) that meet regulatory requirements demonstrated removal of canine parvovirus (CPV). CPV is a model virus for pathogenic nonenveloped viruses, including parvovirus B19, not adequately removed or inactivated by most processes currently in practice. The recovery of proteins from plasma with high purity, recovery, and function, while simultaneously removing viruses, provides blood products with a level of purity compatible with clinical use more quickly and cheaply than available techniques.     

Molecular dynamics investigation of oxygen vacancy diffusion in rutile

Oxygen vacancy diffusion in rutile was studied by Born-Oppenheimer molecular dynamics techniques in the framework of the semiempirical molecular orbital method MSINDO. Migration of an oxygen vacancy from the rutile (110) surface towards the bulk was simulated. The metadynamics technique was employed to accelerate the diffusion processes. In this way, transition state structures and activation energies for the diffusion processes were obtained. Rate constants and the time scale of diffusion processes were estimated for different temperatures using the calculated activation energy. It was found that the vacancies in the bulk are less stable than on the surface. The feasibility of oxygen vacancy diffusion under experimental conditions is discussed.     

Chemical oscillations in the uncatalyzed bromate oxidation of hydroquinone and nitrophenols

Chemical oscillatory behavior in the uncatalyzed bromate oxidation of hydroquinone and nitrophenols is reported. The reaction is strongly inhibited by stirring. Effect of one-electron redox couples (EZ catalysts) on the system is described.

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. . - ( EZ) .

     

Cycloadditions of 8,8-dicyanoheptafulvene to styrenes: manifestation of dual reactivity modes

A facile cycloaddition reaction of 8,8-dicyanoheptafulvene with styrenes leading to the corresponding [8+2] and [4+2] adducts in excellent yields is described.     

On theC p toC v conversion of solid linear macromolecules II

A modification is proposed for the Nernst-Lindemann equation that is used to convert calculated heat capacities at constant pressure (C _p ) to heat capacities at constant volume (C _v ) for solid, linear macromolecules. the constant A₀ per mole of repeating unit in this equation is derived by taking into account the variable number of vibrators excited at different temperatures. With the new equation it is possible to calculateC _p for solid polymers over a wider temperature range. The constant is calculated for solid polymers from experimental thermal expansivity, isothermal compressibility and heat capacity data obtained from the literature. An average value of (3.9±2.4)×10^–3(K mol)/J was obtained for A₀ (new) from data on 22 solid polymers. This average value may be used as a universal constant in case no experimental data on compressibility and expansivity are available for computation ofA ₀. The remaining variation of A₀ (new) with temperature is discussed and example calculations are shown for polyethylene. Effects of premelting and possibly large-amplitude motion are discovered for polyethylene in the temperature range 290 to 410 K.

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Zusammenfassung Es wurde eine Abänderung der Nernst-Lindemann Gleichung vorgeschlagen, mit deren Hilfe für feste, lineare Makromoleküle errechnete Wärmekapazitäten bei konstantem Druck (C _p ) in Wärmekapazitäten bei konstantem Volumen (C _p ) umgerechnet werden können. Zur Ableitung der molaren Konstanten A₀ in dem sich wiederholenden Teil der Gleichung wurde die variable Anzahl der erregten Schwinger bei verschiedenen Temperaturen berücksichtigt. Mit der neuen Gleichung wird es möglich, dieC _p fester Polymere für einen breiten Temperaturbereich zu errechnen. Die Konstante wurde für die festen Polymere auf Grund des ermittelten thermischen Ausdehnungsvermögens und der isothermen Kompressibilität sowie der der Literatur entnommenen Wärmekapazitätsangaben berechnet. Aus Angaben von 22 festen Polymeren wurde für A₀(neu) ein Durchschnittswert von (3,9±2,4)×10^–3 (K mol)/J erhalten. Verfügt man zur Berechnung von A₀ über keine experimentellen Werte für Kompressibilität und Ausdehnungsvermögen, so kann dieser durchscnittswert als universale Konstante angewendet werden. Die verbleibende Temperaturabhängigkeit von A₀(neu) wird besprochen und Beispielrechnungen für Polyäthylen gegeben. Für Polyäthylen wurden im Temperaturbereich 290 bis 410 K Effekte durch Vorschmelzen und Bewegungen mit großer Amplitude festgestellt.

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-, (C _p ) (C _v ) , . A ₀ , . C _p . A ₀ , , . 22 , A ₀ () (3,9±2,4)· 10^–3 ·/. A ₀ . A ₀ , . 290–410 .

     

One-electron redox reactions of troxerutin in aqueous solutions

The oxidation of flavonoids is of great interest because of their action as antioxidants with the ability to scavenge radicals by means of electron-transfer processes. The redox reactions of the flavonoid derivative troxerutin, (2-[3,4-bis-(2-hydroxyethoxy) phenyl]-3[[6-deoxy-α-L-manno-pyranosyl)-β-(D-glucopyranosyl]-oxy]-5-hydroxy-7-(2-hydroxyethoxy)-4H-1-benzo-pyran-4-one), were investigated over a wide range of conditions, using pulse radiolysis and cyclic voltammetry. The oxidation mechanism proceeds in sequential steps. One-electron redox potentials for troxerutin were found to be +1.196, +0.846 and −0.634 V vs. NHE.     

Extraction of tri- and tetravalent actinides with dihexyl N,N-diethylcarbamoylmethyl phosphonate (DHDECMP) and TBP from nitric acid solutions

Extraction of trivalent (Pu³⁺, Am³⁺, actinides and Eu³⁺, a representative of lanthanides) and tetravalent (Np⁴⁺ and Pu⁴⁺) actinides has been studied with dihexyl N,N-di-ethylcarbamoylmethyl phosphonate (DHDECMP) in combination with TBP in benzene from 2M nitric acid. The stoichiometries of the species extracted were found to be M(NO₃)₃·(3–n) TBP·n DHDECMP (for trivalent ions) and M(NO₃)₄·(2–n) TBP·n DHDECMP (for tetravalent ions) by the slope ratio method. The extraction constants evaluated (from the distribution data) indicate that for tetravalent ions (with solvation number two) the extraction constant increases when TBP (Kh=0.17) molecules are successively replaced by more basic DHDECMP (Kh=0.34) molecules. However, for trivalent ions (with solvation number three) when TBP molecules are totally replaced by DHDECMP molecules stereochemical factors appear and instead of increase, a substantial decrease in extraction constants is observed for Eu³⁺ and Am³⁺, a lesser decrease being observed for Pu³⁺ (larger ion).