A highly efficient general synthesis of phosphine-borane complexes

A general synthesis of phosphine-borane complexes proceeding in high yield in a safe, green process from borane generated in situ from sodium borohydride is described. The procedure also allows simultaneous carbonyl reduction and phosphine-borane formation on air-sensitive bulky phosphine derivatives.     

Recyclability of a layered silicate-thermoplastic olefin elastomer nanocomposite

A multiple-pass study was undertaken with a layered silicate-thermoplastic olefin elastomer (TPO) nanocomposite to study the impact of processing history on the properties of the material. A set of 10 passes were completed through a co-rotating intermeshing twin-screw extruder with samples collected to monitor changes in the composite. The microstructure of the nanocomposite was characterized using TEM, XRD, FT-IR, steady and complex shear rheology, and mechanical testing. With progressive passes through the extruder, the TPO nanocomposite experienced both delamination of the organoclay as well as thermo-oxidative degradation. The onset and extent of degradation were found to be unaffected by the presence of the organoclay species in the polymer, though, inclusion of a maleated compatibilizer led to increased chain scission. The generated carbonyl groups along the polymer chain as a result of oxidation were speculated to have a significant effect on the developing percolating network of clay within the material and on the final rheological properties of the composite. Despite the occurrence of degradation in the nanocomposite during recycling, its rheological and mechanical properties remained significantly higher than those of the unfilled resin.     

A modification of the heteropoly blue method for the microgram determination of arsenic in biological materials

Summary A sensitive method has been developed for analysis of trace amounts of arsenic in biological materials using the heteropoly blue method. The method employs a closed apparatus and a nitrogen atmosphere, and allows the detection of arsenic in ppm concentration using samples of 100 mg.

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Zusammenfassung Eine empfindliche Methode zur Bestimmung von Arsenspuren in biologischem Material im Wege der Molybdänblaumethode wurde ausgearbeitet. Man arbeitet dabei in einer geschlossenen Apparatur in Stickstoffatmosphäre und kann so in 100-mg-Proben Arsenkonzentrationen in der Größenordnung von ppm bestimmen.

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Presented at the 6th Annual Northeast Regional Meeting of the American Chemical Society, Burlington, Vermont, August 19, 1974.     

Reactions of tetracarbonylcobaltate(-I) with chlorosilanes in ether solvents

The reactions of NaCo(CO)₄ with Me_nSiCl_4?n (n = 0–3) in diethylether (Et₂O) and in tetrahydrofuran (THF) have been studied. Three distinct reaction pathways were recognised which depend on the acidity of the chlorosilane and basicity of solvent. Attack at the silicon centre via the Co atom of Co(CO)₄^? leads to formation of a SiCo bond; reaction involving a CO ligand of Co(CO)₄^? gives clusters R₃SiOCCo₃(CO)₉; and chlorosilane induced attack of Co(CO)₄^? on the solvent gives products derived from THF molecules.     

Über das wechselvolle Bild der Kinetik bei Umsetzung von Permanganat mit überschüssigem Wasserstoffsuperoxyd

Zusammenfassung Es wird der Versuch unternommen, die eigenartigen und unreproduzierbaren Verhältnisse bei der Permanganat-Wasserstoffsuperoxyd-Reaktion, sofern Wasserstoffsuperoxyd im Überschuß zugegen ist, nicht, wie dies bisher angenommen wurde, einer unter solchen Umständen vermuteten Eigenart dieser Umsetzung zuzuschreiben, sondern dem zwischenzeitlichen Auftreten einer schnell wieder verschwindenden Heterogenität; letztere wird auf intermediäre Hydrolyse des Mn⁴⁺-Ions unter Bildung von Mn(OH)₄(MnO₂) zurückgeführt. Die Folgerungen aus dieser Annahme werden diskutiert; der merkwürdige Einfluß der Rührung und ihrer Geschwindigkeit wird gedeutet.     

Reactions of C(6)F(5)Li with tetracyclone and 3-ferrocenyl-2,4, 5-triphenylcyclopentadienone: An (19)F NMR and X-ray crystallographic study of hindered pentafluorophenyl rotations

Tetracyclone, 2a, reacts with C(6)F(5)Li to yield 2-pentafluorophenyl-2,3,4,5-tetraphenylcyclopent-3-en-1-one, 7, and 5-hydroxy-5-pentafluorophenyl-1,2,3,4-tetraphenylcyclopentadiene, 8, as the result of 1,6 and 1,2 additions, respectively. In contrast, treatment of 3-ferrocenyl-2,4,5-triphenylcyclopentadienone, 2b, with lithiopentafluorobenzene leads to 4-ferrocenyl-4-pentafluorophenyl-2, 3,5-triphenylcyclopent-2-en-1-one, 9, and 5-hydroxy-5-pentafluorophenyl-2-ferrocenyl-1,3, 4-triphenylcyclopentadiene, 10, the products of 1,4 and 1,2 addition, respectively. The structures of 7-9 have been established by X-ray crystallography, and the barriers to rotation (19-21 kcal mol(-)(1)) of the pentafluorophenyl groups in 8-10 have been studied by variable-temperature (19)F NMR. Nucleophilic attack at the ferrocenyl-bearing carbon in 2b is rationalized in terms of a zwitterionic structure in which the positive charge of the "cyclopentadienyl cation" is delocalized onto the iron atom in the organometallic substituent.     

Occupational nuclear medicine: Trace element analysis of living human subjects

Summary Several trace elements are toxic when present in excessive amounts. Such overloads occur most commonly in the occupational setting, although some environmental exposures are also of concern. The relationship between chronic exposure and health effects is best explored with the aid of knowledge of the quantity of element in question stored in the body. In vivo elemental analysis can provide this knowledge non-invasively for a number of elements of toxicological importance. In vivo analysis presents specific challenges, particularly the fact that the body is an extended medium, giving rise to extensive scattering and absorption. Also of primary importance, the radiation dose must be kept as low as reasonably possible and must in every case be within the range of other diagnostic procedures. Both the incident radiation and the detected signal must have an adequate mean free path in human tissue. This means that neutron activation analysis (NAA) and X-ray fluorescence (XRF) are the two most studied techniques. For some elements, analytical methods are established while others are under active development. For still others, no promising technique is currently available. The most fully developed techniques are for lead and cadmium. For lead three different XRF approaches have been put forward, although one, ¹⁰⁹Cd excited K XRF is most widely used. For cadmium, both prompt gamma NAA and XRF have been developed to the extent of full human studies. Amongst elements for which application to human studies has begun or is likely to begin shortly are aluminum and manganese, both using NAA.     

A systematic study of magnetic order in divalent europium perovskites

The magnetic properties of a series of cubic perovskite materials, Eu(Al_0.5Ta_0.5)O₃, Eu(Mg_0.5W_0.5)O₃, and Eu(Lu_0.5Ta_0.5)O₃ have been investigated using bulk magnetic and Mössbauer techniques. Eu(Al_0.5Ta_0.5)O₃ is a ferromagnet (T_c ～ 5°K, θ_c = + 8°K), Eu(Lu_0.5Ta_0.5)O₃ is an antiferromagnet (T_N = 4.0, θ_c = ?8°K), while Eu(Mg_0.5W_0.5)O₃ is probably antiferromagnetic (T_N = 2.8°K, θ_c = ? 1°K). These data are compared with the known properties of EuLiH₃ and EuTiO₃ and a sharp drop in θ_c as a function of increasing lattice constant is noted. A molecular field theory analysis of the data yields two possible sets of nn (J₁) and nnn (J₂) exchange constants for each compound which are compared with existing theories.     

ACTION SPECTRUM FOR ANTHRACENE-INDUCED PHOTOSENSITIZATION OF HUMAN SKIN

Abstract— The action spectrum for photosensitization by topically applied anthracene was determined in human volunteers. Spectral reactivity was demonstrated in the range between 320 and 380 nm, with peak activity at around 360 nm. Three distinct inflammatory responses viz. immediate transient erythema, delayed erythema, and wealing were evoked following exposure to effective wavelengths. The action spectra for these responses were similar but the threshold doses were different. Prior treatment with a mast cell degranulating agent (codeine) abolished anthracene-UVA induced wealing but did not influence the erythema response. These findings suggest that photosensitized damage to cutaneous mast cells may be partially responsible for some of the observed inflammatory responses, but other sites of photochemical injury are also involved.     

Rapid determination of molybdenum in ferromolybdenum and molybdenum additives, with oxine

A rapid method is presented for the gravimetric determination of molybdenum (as the oxinate) in ferromolybdenum and molybdenum additives. The sample is fused with a mixed flux of sodium peroxide and sodium carbonate in a zirconium crucible for complete decomposition. Leaching the cooled fusion cake with water provides instantaneous separation of molybdenum as sodium molybdate from iron(III) and other hydrous oxides. After filtration, the molybdenum is precipitated with oxine after addition of EDTA and oxalate to obviate interference from other metal oxinates, and determined gravimetrically. The precision and accuracy are comparable to those of referee methods.