The reaction of n-butyllithium and potassium t-amyloxide with butenes

1-Butene, cis/trans-2-butene and 2-methylpropene were polymetalated by treatment with the product obtained by combination of n-butyllithium and potassium t-amyloxide. Polymetalation was determined by quenching with deuterium oxide and analysis by gas chromatograph-mass spectrometer combination. The rate of metalation was followed by n-butane evolution. Approximately 20% of cis-2-butene exclusively was realized after H₂O quench of the reaction of 1-butene/n-butyllithium/ potassium t-amyloxide for 1.0 h at room temperature. A small amount (7%) of a cis/trans-2-butene mixture was isomerized to 1-butene and the remaining 2-butene was enriched in the cis-isomer. The assumption that n-butylpotassium was the active metalating species was confirmed by the dependency on lithium/potassium ratio, relative ease of organometallic decomposition at 70°, rapid reaction with monochlorostyrene at room temperature, and the similarity to organosodium and organopotassium isomerization of olefins.     

Determination of trace elements in biological standard kale by neutron activation analysis

Fifteen elements at trace levels have been determined by neutron activation analysis in the biological standard kale distributed byBowen. La, Br, As, Se, Sc, Ag, Zn, Co, Cr, Sb, Eu, Fe, and Zr have been determined by a nondestructive technique using a high-resolution Ge(Li) detector. Two more elements, Au and Hg, have been determined after radiochemical separation. The nondestructive procedure is shown to yield data in generally good agreement with those obtained by destructive techniques. Potential sources of error in the nondestructive technique are discussed.     

1,2,4-Triazoles—XXXIII: Photodimerization of some sym-di(3-s-triazolo-[4,3-a]pyridyl)-alkanes and related derivatives

Irradiation of 3,3'-[ethane-1,2-diyl]bis-[1,2,4-triazolo-[4,3-a]pyridine] at 300 nm gave the cisoid-fused cyclobutane dimer 5aα,5bα-10bα,10cα-tetrahydro-1,10-ethano-2,3,8,9,10a,10d-hexaazadicyclopenta[a,i]biphenylene. Under the same conditions 3,3'-[propane-1,3-diyl]bis-[1,2,4-triazolo[4,3-a]pyridine] gave the corresponding cyclobutane dimer, 5aα,5bα,10bα,10cα-tetrahydro-1,10-propano-2,3,8,9,10a,10d-hexaazadicyclopenta[a,i]biphenylene whereas at 254 nm the photoproduct obtained had the “cage-like” structure 3b,3c,3d,3e,6b,6c,6d,6e-octahydro-3, 4-propano-1,2,3a,3f,5,6-hexaazadicyclobuta[def,jkl]dicyclopenta[b,h]biphenylene. Replacement of the hydrocarbon linkage with the oxybis(methylene) or a thiobis(methylene) unit and irradiation at 300 nm gave the corresponding cisoid-fused, cyclobutane dimers only. The effect of methyl substituents in the pyridine ring of the bicyclic system on the dimerization process was also studied.     

Röntgenkleinwinkeluntersuchungen an Lösungen von Schweineserum-Albumin bei verschiedenen pH-Werten

Zusammenfassung Schweineserum-Albumin wurde nach sorgfältiger Reinigung bei den pH-Werten 7,0, 5,1 und 3,7 mit Hilfe der Röntgenkleinwinkelstreuung untersucht. Es wurde bei allen Messungen praktisch dasselbe Molekulargewicht gefunden: der Mittelwert liegt bei 70 300±2 500. Die Ermittlung der Streumassenradien ergab bei pH 7,0 und pH 5,1 ähnliche Werte (33,0 Å bzw. 31,1 Å), bei pH 3,7 dagegen einen Wert von 37,8 Å. Die Formbestimmung ergab bei pH 7,0 und pH 5,1 identische Achsenverhältnisse (0,75 : 1 : 2), während bei pH 3,7 ein solches von 0,2 : 1 : 1 gefunden wurde.

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X-ray small-angle scattering investigations on solutions of porcine serum albumin at differentpH-values

Higly purified samples of porcine serum albumin were measured by the X-ray small-angle scattering method at pH 7.0, 5.1, and 3.7. The molecular weight is found to be the same in all three cases: the mean value is 70 300±2 500. The radius of gyration is 31.1 Å and 33.0 Å at pH 5.1 and 7.0 resp., whereas at pH 3.7 a value of 37.8 Å is found. The determination of the molecular conformation yields a similar axial ratio at pH 5.1 and pH 7.0 of 0.75 : 1 : 2; at pH 3,7 we find an axial ratio of 0.2 : 1 : 1 to be consistent with the scattering curves.

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Herrn Prof. Dr.H. Nowotny gewidmet.     

The correlation of NMR chemical shifts with EHT calculated electron densities for 3-pyridinols

The NMR spectra of a series of five 3-pyridinols in dioxane and dimethyl sulfoxide have been correlated with electron densities calculated by the Extended Hückel MO method. The data were found to fit a straight line of the form y=ax+b. The effects of hydrogen-bonding between pyridinol molecules on the correlation have been considered, and they have been estimated quantitatively for 6-methyl-3-pyridinol via Extended Hückel Calculations on a hydrogen-bonded model.

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Zusammenfassung Die Kernresonanzspektren von fünf 3-Pyridinolen in Dioxan und Dimethylsulfoxyd wurden mit den Elektronendichten aus dem erweiterten Hückelverfahren korreliert, und zwar ergibt sich eine lineare Beziehung. Der Einfluß von intermolekularen Wasserstoffbrücken ist für einen Fall (die 6-Methyl-Verbindung) durch EHT-Rechnungen festgestellt und in den übrigen Fällen geschätzt worden.

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Résumé Les spectres NMR d'une série de cinq 3-pyridinols dans le dioxane et le diméthyle-sulfoxyde ont été corrélés avec les densités électroniques calculées par la méthode de Hückel Etendue. Les données se placent correctement sur une droite y=ax+b. Les effets de la liaison hydrogène entre les molécules de pyridinol ont été envisagés et estimés quantitativement pour le 6-méthyl-3-pyridinol par des calculs EHT sur un modèle à liaison hydrogène.

     

Empfindliche Methode zur Bestimmung geringer Schwefelgehalte in Wolframoxiden und Wolframpulvern

Zusammenfassung Der Schwefel in Wolframoxiden und Wolframpulvern wird im Wasserstoffstrom bei 800°C in H₂S übergeführt, der in Cadmium-Zinkacetat-Lösung absorbiert und anschließend jodometrisch titriert wird. Die Anwesenheit von WO₃ ermöglicht eine quantitative Umwandlung von Sulfatschwefel in H₂S. Die Standardabweichung beträgt für ein Wolframoxid mit 310 ppm S±13 ppmS und für ein Wolfram-Metallpulver mit 45 ppm S±1 ppm S.

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Sulfur is converted into hydrogen sulphide by hydrogenation at 800°C. This H₂S is absorbed in a cadmium-zinc acetate solution and titrated iodometrically. The presence of WO₃ makes possible a quantitative conversion of sulphate sulphur into H₂S. The standard deviation is ±13 ppm S for WO₃ containing 310 ppm S, and ±1 ppm S for metallic tungsten powder containing 45 ppm S.

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Herrn Prof. Dr.E. Hayek zum 60. Geburtstag gewidmet.     

Reagents for Organic Synthesis : Vol. 5; by M. Fieser and L.F. Fieser,Wiley-Interscience,New York/London/Sydney/Toronto, 1975, 864 pages, $32.15, £16.15.

Phosphorus-31 NMR and X-ray crystallography show that the two similar chelating triphosphine ligands PhP(CH₂CH₂PPh₂)₂(2,2-P₃) and PhP(CH₂CH₂CH₂ PPh₂)₂(33-P₃) form cobalt(I) complexes having trigonal-bipyramidal and square-pyramidal structures, respectively. The structures and PP coupling constants of [Co(33-P₃)(P(OMe)₃)CO]BF₄·1THF and [Co(22-P₃)(P(OMe)₃)₂]BF₄ are given, and the change from square-pyramidal geometry in [Co(33-P₃)P(OMe)₃)CO]⁺ to trigonal-bipyramidal in [Co(22-P₃)(P(OMe)₃)₂]⁺ may be rationalized in terms of a decreased “chelate bite angle” for the PhP(CH₂CH₂PPh₂)₂ ligand.     

The electronic structure of molecules by a many-body approach : II. Ionization potentials one-electron properties of pyridine and phosphoridine

The valence ionization potential (IPs) of pyridine and phosphoridine are studied by an ab initio many-body approach which includes the effects of electron correlation and reorganization beyond the Hartree-Fock approximation. For pyridine the order of the first three IPs is a₂(π), a₁(n), b₁(π), but the IPs of the a₂ and a₁ orbitals are so close together that they have to be regarded as identical in binding energy, which is also concluded from experiment. Whereas for pyridine the ordering of the IPs calculated in the HF approximation is incorrect, it is correct for phosphoridine. For this latter molecule the first three ionization potentials are due to ionization from the b₁(π), a₂(π), and a₁(n) orbitals. Several one-electron properties are calculated and compared with experimental and other theoretical data. The localized molecular orbitals are discussed as well.     

Long-range interaction between 1s and 2s or 2p hydrogen atoms

Long-range interaction energy between two hydrogen atoms has been computed in the second order of the perturbation theory. All states of the system arising when one of the atoms is in the 1s and the other in the 2s or 2p state have been considered. The energy represented by a series expansion in inverse powers of the internuclear distance, R, has been computed up to the terms in R^?8. The results are believed to give reliable interaction energies for R > 15 a.u. Accurate interaction energy for two ground-state hydrogen atoms has also been obtained up to the terms in R^?10. Results for the B′ ¹∑ state are employed to discuss the experimental ground-state dissociation energy of H₂, D₂, and HD. For H₂ all values of the dissociation energy obtained from various experimental absorption limits, by using the computed potential energy curve to separate off the effect of rotation, are shown to be satisfactorily consistent. The resulting total energy of H₂ is, however, higher than the most accurate theoretical value.