Die Beziehungen zwischen Adsorptionswärmen,Oberflächen-spannungen und Reaktionswärmen bei dem ReaktionstypusA starr +B gasförmig ⇄AB starr

Zusammenfassung Wird die gesamte Energietönung eines Vorganges vom TypusA starr +B gasförmig AB starr mitE ₁ bezeichnet, die Energie der Chemoadsorption vonB anAB mitE ₂, die der Oberflächenspannung entsprechende, auf 1 Mol sich beziehende Oberflächenarbeit bei der PhaseA mitE ₃ und bei der PhaseAB mitE ₄, so besteht die BeziehungE ₁ +E ₃ –E ₂ –E ₄ =0 . Der isotherme Abbau nach derGibbsschen Funktion kann nur stattfinden, wennE ₃ vergleichsweise sehr groß (unendlich) ist, derjenige nach derLangmuirschen Funktion, wennE ₃ sehr klein (Null) ist.     

Reaktionen an komplexgebundenen liganden: XXXVI. Synthese und oxidationsverhalten von M(CO)5-komplexen (M = Cr,Mo, W) mit amin- und benzochinondiimin-liganden

The oxidation of yellow Cr(CO)₅NH₂R complexes (NH₂R = aniline, m-toluidine, 3,5-xylidine, m-anisidine) with Pbac₄ gives deep blue to deep purple coloured compounds, which have been identified as the respective [Cr(CO)₅(N-phenyl-1,4-benzochinon-diimine)] complexes. Oxidation of the p-phenylenediamine complex yields [(OC)₅CrHNC₆H₄NHCr(CO)₅], which is also deep blue. The binuclear blue complex [{Cr(CO)₅}₂HNC₆H₄NC₆H₅] is obtained by treating Cr(CO)₅THF with the free ligand in THF/hexane; it dissociates rapidly in acetone to form [Cr(CO)₅HNC₆H₄NC₆H₅] and Cr(CO)₅. Analogous Mo(CO)₅ and W(CO)₅ complexes could not be obtained. The oxidation of [W(CO)₅(m-anisidine)] by I₂ yields [W(CO)₄I]₂. All the compounds were characterized by spectroscopic methods as well as by elemental analysis.     

ESR.-Spektrum von Diphenylpicrylhydrazyl (DPPH)

The ESR. sprectra of DPPH in mixed organic solvents have been measured with a K-band superheterodyne spectrometer and self-locking magnetometer with high precision. Approximately 150 lines have been resolved in the spectra. Both the zero and first order derivative spectra were analyzed by a line shape analysis program for determination of the coupling constants. The smallest coupling constant was found to be 377 ± 5 mG, all other coupling parameter are multiples of this constant. A set of most probable coupling constants is given. The two nitrogen coupling constants are found to be equal within experimental error, and there exist several rotational relations and several possible assignments.     

Electronic detection of the enzymatic degradation of starch

[reaction: see text] The enzymatic degradation of starch can be monitored electronically using single-walled carbon nanotubes (SWNTs) as semiconducting probes in field-effect transistors (FETs). Incubation of these devices in aqueous buffer solutions of amyloglucosidase (AMG) results in the removal of the starch from both the silicon surfaces and the side walls of the SWNTs in the FETs, as evidenced by direct imaging and electronic measurements.     

Influence of structural changes on the ion selectivities of magnesium ionophores based on malonic acid diamides

In an investigation of octamethylene bis(malonic acid diamides) and their selectivities for magnesium, it was found that presence of secondary amides within the particular ionophore played a considerable role in the enhancement of magnesium selectivity. Similar effects in other ionophores, i.e. tris(malonic acid diamides), were thus systematically looked at with the help of selectivity measurements with the hope of optimizing the number of secondary and tertiary amides so as to improve the magnesium selectivity. The syntheses of several investigated tris(malonic acid diamide) isologues are equally reported.Deceased in November 1992     

A vibrational spectroscopic study of the adsorption of 4,4′-bipyridyl by sepiolite and smectite group clay minerals from Anatolia (Turkey)

The adsorption of 4,4-bipyridyl by natural sepiolite and smectite group clay minerals (bentonite, hectorite and saponite) from Anatolia (Turkey) has been studied using vibrational spectroscopy. Investigation of Fourier-transform infrared and Fourier-transform Raman spectra of adsorbed 4,4-bipyridyl indicate the presence of chemisorbed species. However, any evidence for the generation of anionic species on the surface of the phyllosilicates has not been detected. It is proposed that the adsorbed bipyridyl molecules on sepiolite are centrosymmetric and H-bonded to the surface hydroxyls through both the nitrogen lone pairs as bidentate ligands. The adsorbed bipyridyl molecules on the smectite group clays are coordinated to exchangeable cations both directly and also indirectly through water as monodentate ligands. XRD patterns of the clays studied are also recorded.     

Sparteine-mediated asymmetric nucleophilic substitution at prochiral, sp(3)-hybridized carbon

[reaction: see text] ++-Phenyl-1,3-dioxolanes (1) react with organolithium reagents (2), associated with (-)-sparteine, in the presence of BF(3).OEt(2) to afford chiral monosubstitution products 3. Enantioselectivity is highest if both 1 and 2 carry alkyl substituents in the ortho position. However, the enantioselectivity decreases in the case of very bulky substituents such as tert-butyl or phenyl.     

Selective C-arylation of free (NH)-heteroarenes via catalytic C-H bond functionalization

A new system for palladium-catalyzed arylation of a broad spectrum of free (NH)-heteroarenes has been developed (indole, pyrrole, pyrazole, 2-phenylimidazole, imidazole, benzimidazole, and purine). Remarkable selectivity has been achieved in the presence of MgO base, providing single C-arylation products, while no N-arylation and no bis-arylation products have been detected. In the case of free imidazole, exclusive C-4 arylation may be switched to exclusive 2-arylation by the addition of CuI to the Pd/Ph3P/MgO system. When free aryl-(NH)-azoles are desired, direct arylation eliminates three steps in comparison to standard methods, including N-protection, stoichiometric metalation or halogenation, and N-deprotection.     

Thermal and photochemical studies with stilbene oxides intramolecular trapping of carbonyl ylide intermediates

The annelated tetrahydrofuran derivatives 14 and 15, resp., are formed in moderate yield by intramolecular trapping reaction of the carbonyl ylide intermediates 9, which are generated either by thermal ring opening of the trans-stilbene oxides 7t/8t or by photolysis of the cis-isomers 7c/8c.     

Simultaneous quantification of budesonide and its two metabolites, 6beta-hydroxybudesonide and 16alpha-hydroxyprednisolone,in human plasma by liquid chromatography negative electrospray ionization tandem mass spectrometry

A sensitive, rapid and selective liquid chromatography negative electrospray ionization tandem mass spectrometry [LC-(-)ESI-MS-MS] method has been developed and validated for the simultaneous quantification of budesonide (BUD) and its major metabolites, 6beta-hydroxybudesonide (OH-BUD) and 16alpha-hydroxyprednisolone (OH-PRED) in human plasma. The method was validated over a linear range from 0.1 to 10 ng/mL for all three analytes using a solid-phase extraction procedure with 9-fluoro-hydrocortisone as the internal standard. The between-day and within-day coefficients of variation for all compounds were < or =20% at the concentrations of lower limit of quantification and < or =15% at other quality control concentrations. The utility of this assay was demonstrated by monitoring BUD, OH-BUD and OH-PRED plasma concentrations in one healthy subject for 24 h following a 3 mg oral dose of budesonide, administered as a pH modified release capsule (Budenofalk) to healthy volunteers.