Synthesis and x-ray crystal structure of the TiMgCl5(OOCCH2Cl) · (ClCH2COOC2H5)3 Adduct

The synthesis of the TiMgCl₅(OOCCH₂Cl) · (ClCH₂COOC₂H₅)₃ adduct, obtained by reacting TiCl₄ with a solution of MgCl₂ in dry ClCH₂COOC₂H₅, is reported together with its molecular and crystal structure as determined by x-ray diffraction. The structure was solved by direct and Fourier methods and refined by least-squares techniques to R = 0.057 for 1318 independent observed reflections. Crystals are monoclinic, space-group P2₁/c, with 4 formula units in a unit-cell of dimensions a = 10.480(4), b = 19.641(9), c = 16.597(6) Å, β = 120.21(5)°. The titanium(IV) atom is octahedrally coordinated by five chlorine atoms and an oxygen atom of a OOCCH₂Cl residue. The magnesium atom is similarly coordinated by two chlorine atoms, the carbonyl oxygen atoms of three ClCH₂COOC₂H₅ molecules and an oxygen atom of the OOCCH₂Cl residue. The two octahedra share an edge by a double chlorine bridge between the magnesium and the titanium atoms and are also connected by the COO group of the OOCCH₂Cl residue. Changes in the configurations and dimensions with respect to the free acceptor and donor molecules are discussed.     

Natural and artificial radionuclides in soils from Paraná State,Brazil

Soil samples from Paraná State, Brazil, were collected in 1991 and compared with others collected at the same location in March 1977 and at the end of 1983. Pedological analyses were practiced on these samples and¹³⁷Cs and²³²Th,²²⁶Ra and⁴⁰K activities were determined by gammaray spectrometry. A latitude dependence of¹³⁷Cs was found as well. It was impossible to determine the¹³⁷Cs contribution from Chernobyl nuclear accident because of low fallout and intense leaching, erosion and re-suspension in soils of regions with high annual precipitation. Natural radionuclides did not show such effects.     

Determination of the Enthalpies of Vaporization of Cyclic Organic Peroxides by Correlation of Changes in Gas Chromatographic Retention Times

Liquid and solid cyclic peroxides derived from aliphatic ketones are explosive materials so their enthalpies of vaporization and other thermodynamic or condensed-phase properties cannot be measured directly. In this work the enthalpies of vaporization of peroxides at 298.15 K were estimated simply from gas chromatographic retention times measured at different temperatures. The technique correlates changes in the retention times of compounds whose enthalpies of vaporization are known (called the reference series), with those of the compounds of interest. If t _R′ is the adjusted retention time (retention time of each compound minus the retention time of unretained diethyl ether, used as solvent) a plot of ln t _R′ against 1/T for each compound (reference compounds and cyclic peroxides) results in a straight line (r ² > 0.99 for all compounds). The enthalpy of transfer from solution to the vapor state (Δ_sol^g H _m) can be obtained by multiplying the slope by the gas constant (R). A second plot correlates the enthalpies of transfer from solution to the vapor state (Δ_sol^g H _m), as measured by gas–liquid chromatography (GLC), with enthalpies of vaporization of reference materials (Δ_vap H _m at 298.15 K) available in the literature. C₉–C₁₅ fatty acid methyl esters and hydrocarbons were used as reference compounds. The enthalpies of vaporization of the cyclic organic peroxides were calculated from the equation of the line obtained in this second correlation, the slope of which was Δ_vap H _m (at 298.15 K)/Δ^g _sol H _m. The experiments were performed under isothermal conditions with a DB-5 capillary column, flame-ionization detection (FID), and nitrogen as carrier gas. The column temperature was varied over a range of at least 30–70 K between 403 and 473 K, with chromatograms being acquired at 10 K intervals. Enthalpies of vaporization of cyclic organic peroxides are not available in the literature, and the values given in this paper, obtained by gas chromatography, are the first to be reported.     

Characterization and decomposition mechanism of an unusual nickel, thiocyanate and 4-methylpyridine polymeric complex

The synthesis, characterization, and thermal decomposition of the [Ni(SCN)₂(H⁺SCN)₂(4-mepy)₂] compound with an octahedral structure in polymeric chain were reported, in which SCN groups form bridges among Ni(II) ions. The compound decomposes in water resulting in a pH<4 solution. The FT-IR spectrum presented doublet bands at 2117; 2128 cm⁻¹, 788; 773 cm⁻¹ assigned to ν(C---N) and ν(C---S) stretching modes, respectively, and δ(SCN) deformation modes at 468; 476 cm⁻¹. The Raman spectrum of the compound presented the ν(C---N) stretching as a strong doublet at 2122; 2128 cm⁻¹, ν(C---S) at 783; 770 cm⁻¹, and δ(SCN) at 468; 477 cm⁻¹. No significant changes were observed in the 4-mepy ligand bands compared with the vibrational frequencies of the pure compound or the compound in aqueous solution 0.2 mol l⁻¹. The crystal UV–vis reflectance spectrum presented two bands centered in 626 and 424 nm tentatively assigned to the d→d type transitions, ³A_2g→³T_1g and ³A_2g→³T_1g, for a symmetry close to O_h. The TG curve showed a mass loss between 120 and 200 °C assigned to the loss of the two 4-mepy molecules; from 200 to 265 °C, the loss of the two H⁺SCN groups; and from 265 to 450 °C, the loss of the two SCN groups that formed the bridges among the nickel atoms. Based on these mass loss data, a mechanism of thermal decomposition for the compound was proposed.     

Development and validation of a rapid RP‐HPLC method for analysis of (−)‐copalic acid in copaíba oleoresin

The Copaifera species (Leguminoseae) are popularly known as ‘copaíba’ or ‘copaíva’ and are grown in the states of Amazonas, Pará and Ceará in northern Brazil. The oleoresins obtained from these species have been extensively used owing to their pharmacological potential and their application in cosmetic and pharmaceutical preparations. In the present study, the development and validation of a novel, rapid and efficient RP‐HPLC methodology for the analysis of the diterpene (?)‐copalic acid (CA), pointed out as the only chemical marker of the Copaifera genus, are described. The regression equation (Y = 26,707x ? 29,498) was obtained with good linearity (r² = 0.9993) and the limits of quantification and detection were 9.182 and 3.032 µg/mL, respectively. The precision and the accuracy of the method were adequate (lower than 4%). Finally, the validation parameters evaluated were satisfactorily met, so the developed method represents a suitable tool for application in the quality control of such natural products. Further studies aiming to develop analytical methodologies for each Copaifera species using a more representative number of chemical markers should be performed. Copyright © 2012 John Wiley & Sons, Ltd.     

Are Collapse Models Testable via Flavor Oscillations?

Collapse models predict the spontaneous collapse of the wave function, in order to avoid the emergence of macroscopic superpositions. In their mass-dependent formulation, they claim that the collapse of any system’s wave function depends on its mass. Neutral K, D, B mesons are oscillating systems that are given by Nature as superposition of two distinct mass eigenstates. Thus they are unique laboratory for testing collapse models that are sensitive to the mass. In this paper we derive—for the single mesons and bipartite entangled mesons—the effect of the mass-proportional CSL (Continuous Spontaneous Localization) collapse model on the dynamics on neutral mesons. We compare the theoretical prediction with experimental data from different accelerator facilities.     

Screening of Three Transition Metal‐Mediated Reactions Compatible with DNA‐Encoded Chemical Libraries

The construction of DNA‐encoded chemical libraries (DECLs) crucially relies on the availability of chemical reactions, which are DNA‐compatible and which exhibit high conversion rates for a large number of diverse substrates. In this work, we present our optimization and validation procedures for three copper and palladium‐catalyzed reactions (Suzuki cross‐coupling, Sonogashira cross‐coupling, and copper(I)‐catalyzed alkyne‐azide cycloaddition (CuAAC)), which have been successfully used by our group for the construction of large encoded libraries.     

Human Y‐chromosome SNP characterization by multiplex amplified product‐length polymorphism analysis

We designed an allele‐specific amplification protocol to optimize Y‐chromosome SNP typing, which is an unavoidable step for defining the phylogenetic status of paternal lineages. It allows the simultaneous highly specific definition of up to six mutations in a single reaction by amplification fragment length polymorphism (AFLP) without the need of specialized equipment, at a considerably lower cost than that based on single‐base primer extension (SNaPshot?) technology or PCR‐RFLP systems, requiring as little as 0.5 ng DNA and compatible with the small fragments characteristic of low‐quality DNA. By designation of two primers recognizing the derived and ancestral state for each SNP, which can be differentiated by size by the addition of a noncomplementary nucleotide tail, we could define major Y clades E, F, K, R, Q, and subhaplogroups R1, R1a, R1b, R1b1b, R1b1c, J1, J2, G1, G2, I1, Q1a3, and Q1a3a1 through amplification fragments that ranged between 60 and 158bp.