Substituted chromans and tetrahydrofuro[2,3-b]benzofurans (trapped tetrahedral intermediates) from 3-phenyl-2-benzofuranones

The previously discovered neighboring group reaction has been extended to the synthesis of chroman derivatives (i.e., 4, 5, 6) containing geminal methyls in the 2-position, a feature common to certain physiologically active natural chromans. In two instances, cyclic ortho ester by-products (8), not observed in previous work, were formed as a result of the intramolecular trapping of tetrahedral intermediates. Reasons for the incursion of this unexpected side reaction are discussed.     

On the magnetic properties and the phase composition of the Cr2O3?MnOx-system (2 ≥ x ≥ 1.5)

The mixed oxide system Cr₂O₃? MnO_x (2 ≥ x ≥ 1.5) was investigated by X-ray diffraction, by measurements of magnetic susceptibility, and by chemical determination of excess oxygen (BUNSEN'S method). The Presence of the antiferromagnetic oxides Cr₂O₃, β-MnO₂, α-Mn₂O₃ and a ferromagnetic phase Cr_1?yMn_yO₂ was stated. The formation of the latter with fourvalent chromium is explained by a lattice induction effect of the MnO₂ (rutile type).     

Electron-impact studies—LXX. Substituent effects in the negative-ion spectra of nitroaryl esters

The negative-ion mass spectra of a variety of substituted nitroaryl benzoates and aryl nitrobenzoates have been studied. Pronounced proximity effects are observed in the spectra of ortho-substituted compounds. The meta and para pairs fragment in a similar manner. Linear plots are observed for many cleavages using either the McLafferty or Harrison methods. Evidence is provided which suggests that the fragmentations of meta and para isomers may proceed by the same mechanistic pathway. The magnitude of ρ does not appear to provide precise information concerning the nature of the transition state for a particular reaction of a negative ion.     

Cl35 NQR spectra and the transmission effects in the series RSO2Cl

Conclusions It was shown by correlating the Cl³⁵ NQR frequencies with the Taft _I and _c parameters that the effect of substituents, which are either capable of conjugation (Hal, OR, NR₂) or are alkyl groups, is transmitted to the chlorine atom through the SO₂Cl group by a practically purely inductive means.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 486–488, February, 1970.     

Chloridionenübergänge in Phenylphosphoroxychlorid, 3. Mitt.: Konduktometrische Untersuchungen

Zusammenfassung Leitfähigkeitsmessungen an Et₄NCl-Lösungen zeigen die Gültigkeit derBjerrumschen Theorie in PhPOCl₂; die Dissoziationskonstante beträgt 1,5·10^–2. FeCl₃ verhält sich nicht wie eine Ionenverbindung, doch ähnlich wie in POCl₃. Zur Verfolgung von Ionenreaktionen wurden konduktometrische Titrationen ausgeführt. ZnCl₂ und AlCl₃ geben 2 Chloridionen, BCl₃, TiCl₄, SnCl₄ und PCl₅ je 1 Chloridion an die Akzeptoren FeCl₃ oder SbCl₅, ab. In Gegenwart von polaren Chloriden nehmen BCl₃, AlCl₃, FeCl₃, PCl₅ und SbCl₅ je 1 Chloridion, ZnCl₂, TiCl₄ und SnCl₄ je nach Angebot 1 oder 2 Chloridionen auf. Sowohl die Chlorometallate, als auch die Chloroniumverbindungen sind im gleichen Ausmaß wie Et₄NCl ionisiert.Mit 4 Abbildungen2. Mitt.:M. Baaz, V. Gutmann, M. Y. A. Talaat undT. S. West, Mh. Chem.92, 150 (1961).Herrn Prof. Dr.L. F. Audrieth zum 60. Geburtstag gewidmet.     

Kristallstruktur von Hexamincyclotriphosphazen,P3N3(NH2)6

Crystal Structure of Hexamine Cyclotriphosphazene, P₃N₃(NH₂)₆ In the presence of KNH₂ hexamine cyclotriphosphazene semi ammoniate (molar ratio 12:1) in NH₃ gives crystals of solvent free P₃N₃(NH₂)₆ within 5 d at 130°C and p(NH₃) = 110 bar. The structure was solved by X-rax methods: P₃N₃(NH₂)₆: P2₁/c, Z = 4, a = 10.889(6) Å, b = 5.9531(6) Å, c = 13.744(8) Å, β = 97.83(3)°, Z(F_o) = 1 721 with (F_o)² ≥ 3σ(F_o)², Z(var.) = 157, R/R_w = 0,036/0,041 The structure contains columns of molecules P₃N₃(NH₂)₆ all in the same orientation. The six-membered rings within one molecule have boat conformation. The columns are stacked together in a way that one is surrounded by four others shifted by half a lattice constant in direction [010]. Strong hydrogen bridge-bonds N? H…?N connect molecules within the columns and between them.     

Temperature-programmed reduction and oxidation of bimetallic Pd?Ni/Al2O3 catalysts

Temperature-programmed reduction and oxidation of bimetallic catalysts Pd–Ni/Al₂O₃ seem to indicate phase segregation of palladium and nickel oxides and alloying of palladium and nickel in the process of reduction of oxidized catalysts.

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- Pd–Ni/Al₂O₃ , .

     

PHYCOBILIPROTEINS: COMPARISON OF SOLUTION AND SINGLE CRYSTAL FLUORESCENCE FOR C-PHYCOCYANIN AND B-PHYCOERYTHRIN*

Abstract— Trimeric and hexameric solution forms of C-phycocyanin (CPC) from the cyanophyte Agme-nellum quadruplicatum have been isolated and their spectral properties compared to those obtained from single crystals. Although the absorbance peak of a suspension of small C-phycocyanin crystals is red-shifted only 7 nm relative to the solution forms, the single crystal fluorescence is red-shifted 60 nm relative to the solution forms. The crystal fluorescence spectrum exhibits a single peak at LD_max= 708 nm when excited at 514.5 or 530.9 nm and two peaks (LD_max= 661 and 708 nm) when excitation occurs at 568.2 nm. Fluorescence depolarization measurements indicate that extensive energy transfer could occur for both solution and crystal forms with the latter being dependent upon the relative orientation of the crystal with respect to the excitation dipole. Similar results were obtained with B-phycoerythrin (BPE) from the red alga Porphyridium cruentum where the single crystal fluorescence is red-shifted =50nm relative to the solution spectra with two peaks (LD_max= 583 and 617 nm) observed whose relative intensities are dependent on the excitation wavelength (LD_max– 514.5 and 530.9 nm). Single crystal fluorescent lifetimes exhibited considerable shortening relative to that observed for the solution forms. The implications of these results are discussed with respect to the possible relationships of the crystalline structures to the assembly forms present within phycobilisomes.     

A new method of removing excess of reagent from organic phases in the solvent extraction of metal complex anions with quaternary ammonium salts: Spectrophotometric determination of micro amounts of cobalt with 2-nitroso-1-naphthol-4-sulfonic acid

The removal of excess reagent extracted into an organic phase in the solvent extraction of a metal complex anion with a quaternary ammonium ion is discussed. With a given chelating ligand (HO—R—SO₃H), the order of extractability is HO—R—SO₃^- > M(OR—SO₃)^n- > X^- > ^-O—R—SO₃^- when an anion such as nitrate or halide is added. If suitable amounts of the anion are added, only the excess of reagent can be removed. The principle is applied to the extraction with zephiramine of the cobalt complex anion formed with 2-nitroso-1-naphthol-4-sulfonic acid. Micro amounts of cobalt in pure nickel salts were determined spectrophotometrically.