Synthesis and Molecular and Crystalline Structure of Polyfluoro-1,3-Diazafluorenes

Reactions of 2-amino-3-(1-imino-2,2,2-trifluoroethyl)hexafluoro-1H-indene with carboxylic acid anhydrides and chlorides afforded 2-alkyl(aryl)-4-trifluoromethyl-5,6,7,8,9,9-hexafluoro-1,3-diazafluorenes. The molecular and crystalline structure of the products was studied by NMR spectroscopy and X-ray diffraction. 5,6,7,8,9,9-Hexafluoro-2-phenyl-4-trifluoromethyl-1,3-diazafluorene in crystal gives rise to infinite ladder chains via -stacking interaction between the benzene ring of one molecule and tetrafluorobenzene fragment of the other.     

Synthesis and Structure of Tri-p-tolylantimony Ditosylate

Tri-p-tolylantimony reacts with p-toluenesulfonic acid in the presence of benzoyl peroxide (1 : 2 : 1 molar ratio) in ether to give tri-p-tolylantimony ditosylate in 91% yield. According to X-ray diffraction data, the central antimony atom has the trigonal bipyramidal coordination with the axial location of the tosyl groups. The Sb-O bond lengths are 2.07(2) and 2.17(2) Å; Sb-C bond lengths, 2.08(3), 2.13(3), and 2.13(3) Å; and OSbO bond angle, 175.6(7)°.     

Natural radionuclide-free phosphoric acid production

High-uranium phosphate rock from Itataia, Brazil, was milled for wet-process phosphoric acid production using the dihydrate method. Uranium contained in the phosphoric acid was recovered by solvent extraction. The distribution of long-lived natural radionuclides of the ²³⁸U and ²³²Th decay series involved in these operations was evaluated. ²²⁶Ra, ²²⁸Ra and ²¹⁰Pb were found to predominate in the phosphogypsum, while ²²⁸Th, ²³⁰Th and ²³²Th in the uranium-free phosphoric acid. Thorium is removed from the phosphoric acid by solvent extraction to produce a NORM-free phosphoric acid.     

Magic numbers of large rare gas clusters

The superior stability of closed-shell icosahedral structures is evident from size distributions of argon, krypton and xenon cluster ions in the size range 100?n?1000.     

Organization and polysaccharides of sponge aggregation factor.

Aggregation factor, the macromolecular complex which mediates species-specific aggregation of dissociated sponge cells, was isolated from several species, partially characterized, and visualized by electron microscopy. All factors were large fibrous complexes with a backbone and side chains or arms. In some factors, the backbone is linear. In others it is circular and the complex appears as a sunburst with arms extending like rays from the circle. The size and location of the polysaccharide chains have been studied using purified preparations of Microciona prolifera. "Sunbursts" treated with ethylenediaminetraacetate (EDTA) for 4 weeks at 0 degrees C dissociate into 3 protein- and polysaccharide-containing components. Sodium dodecyl sulfate does not cause the sunburst to dissociate nor does it inhibit dissociation in the presence of EDTA suggesting that dissociation is not due to hydrolytic enzymes. The dissociation products were fractionated on a 977-A pore size micropore glass column. Fifteen percent of the material is excluded and appears in the electron microscope as the central circle of the sunburst. Digestion of the circles with 10(-3) M dithiothreitol (DTT) and 0.5 mg/ml proteinase K for 72 h at 37 degrees C produces 2 polysaccharide chains of 65,000 and 6,000 daltons as fractionated and sized on a 233-A pore size micropore glass column using Pharmacia dextrans as standards. The included fractions of the EDTA-treated material are subunits of the arms which contain 70% of the polysaccharide. A single polysaccharide of 6,000 daltons as measured on 233-A size glass beads and Sephadex G-75 is released from these subunits by proteinase digestion. Pharmacia dextrans are used as standard on both columns. We calculate that there would be four 65,000-dalton chains and one hundred 6,000-dalton chains per circle and fifty 6,000-dalton chains per arm. The third component of the EDTA-treated preparation is partially included on the column. It appears as linear fibrils in the electron microscope and contains polydisperse polysaccharides of several-hundred-thousand daltons. It may be an impurity since there is apparently less than 1 of the large polysaccharide chains per sunburst.     

Reaction of sulphate radical anion (SO<Superscript>.</Superscript><Subscript>4</Subscript><Superscript>-</Superscript>) with hydroxy-and methyl-substituted pyrimidines: a pulse radiolysis study

Reactions of sulphate radical anion (SO·₄ ^-) with 4,6-dihydroxy-2-methyl pyrimidine (DHMP), 2,4-dimethyl-6-hydroxy pyrimidine (DMHP), 6-methyl uracil (MU) and 5,6-dimethyl uracil (DMU) have been studied by pulse radiolysis at pH 3 and at pH 10. The transient intermediate spectra were compared with those from the reaction of hydroxyl radical (·OH). It is proposed that SO·₄ ^- produces radical cations of these pyrimidines in the initial stage. These radical cations are short-lived except in the case of DMHP where a relatively longer lived radical cation is proposed to be formed. When there is a hydrogen atom attached to the N(1) or N(3) position, a deprotonation from these sites is highly favored. When there is no hydrogen attached to these sites, deprotonation from a substituted methyl group is favored. At acidic pH, deprotonation from nitrogen is observed for DHMP, MU and DMU. At basic pH, the radical cation reacts with OH^- leading to the formation of OH adducts.