67,417 research outputs found
SPIN-SPIN COUPLING ACROSS INTERMOLECULAR F-Cl...N HALOGEN BONDS
No full textAuthor Institution: Department of Chemistry, Youngstown State University, Youngstown, OH 44555; Instituto de Qu\imica Medica, CSIC, Juan de la Cierva, 3, E-28006 Madrid, SpainAb initio EOM-CCSD calculations have been performed to determine one- and two-bond spin-spin coupling constants J(F-Cl), J(Cl-N), and J(F-N) across F-Cl...N halogen bonds in complexes with F-Cl as the Lewis acid and N, FCN, HCN, (CH)CN, LiCN, Z-HNNH, HCNH, NHF, NH, cyclic NH(CH), and NH(CH) as Lewis bases. The structures of these complexes were optimized at MP2 with the aug'-cc-pVTZ basis set. The absolute value of J(F-N) increases in these complexes as the F-N distance decreases, a behavior similar to that of J(F-N) for complexes stabilized by F-H...N hydrogen bonds. J(Cl-N) also tends to increase in absolute value with decreasing F-N distance. J(F-Cl) is always positive, decreases upon complex formation as the F-Cl distance increases, and appears to be sensitive to the nature of the nitrogen base. The relatively large differences in the values of these coupling constants in the various complexes and their variation along the chlorine-transfer coordinate for F-Cl...NH suggest that they should be amenable to experimental investigation
Weight-corrected CL/F, showing decrease with age (filled circles: individual estimates for weight-corrected CL/F; lines: median and CI5% and CI95% for CL/F).
No full textWeight-corrected CL/F, showing decrease with age (filled circles: individual estimates for weight-corrected CL/F; lines: median and CI5% and CI95% for CL/F).</p
Clearance (CL/F) vs Age (years).
No full textCL/F increases rapidly during the first year of life, and reaches the reported adult level approximately at 10 years of age (filled circles: individual estimates for CL/F; lines: median and CI5% and CI95% for CL/F).</p
Theoretical Study on Cyclopeptides as the Nanocarriers for Li+, Na+, K+ and F-, Cl-, Br-
No full text
The interaction process between a series of cyclopeptide compounds cyclo(Gly)(n) (n = 4, 6, 8) and monovalent ions (Li+, Na+, K+, F-, Cl-, and Br-) was studied using theoretical calculation. The mechanism of combination between the cyclo(Gly)(n) and ions was discussed through binding energy, Mulliken electron population, and hydrogen bond. It was found that for the same cyclopeptide the binding energy has the order of cyclo(Gly)(n)-Li+ > cyclo(Gly)(n)-Na+ > cyclo(Gly)(n)-K+ and cyclo(Gly)(n)-F- > cyclo(Gly)(n)-Br- > cyclo(Gly)(n)-Cl-. The binding energy manifests the stable complex of cyclo(Gly)(n) and ions can be formed, and the different energy shows the potential use of cyclo(Gly)(n) as nanocarriers for metal ions or the extractant for ions separation.</p
The nature of inter- and intramolecular interactions in F2OXe…HX (X= F, Cl, Br, I) complexes
No full textElectronic structure of the XeOF2 molecule and its two complexes with HX (X= F, Cl, Br, I) molecules have been studied in the gas phase using quantum chemical topology methods: topological analysis of electron localization function (ELF), electron density, ρ(r), reduced gradient of electron density |RDG(r)| in real space, and symmetry adapted perturbation theory (SAPT) in the Hilbert space. The wave function has been approximated by the MP2 and DFT methods, using APF-D, B3LYP, M062X, and B2PLYP functionals, with the dispersion correction as proposed by Grimme (GD3). For the Xe-F and Xe=O bonds in the isolated XeOF2 molecule, the bonding ELF-localization basins have not been observed. According to the ELF results, these interactions are not of covalent nature with shared electron density. There are two stable F2OXe…HF complexes. The first one is stabilized by the F-H…F and Xe…F interactions (type I) and the second by the F-H…O hydrogen bond (type II). The SAPT analysis confirms the electrostatic term, Eelst (1) and the induction energy, Eind (2) to be the major contributors to stabilizing both types of complexes
Si(Cl)H
No full textThe perfluorinated alkoxy silanes {(F3C)(3)CO}(3)SiH (1) and {(F5C6)(3)CO}(2)Si(Cl)H (2) were prepared and fully characterized. Despite the high calculated Bronsted acidities, all attempts to deprotonate 1 and 2 to give the conjugate silanide ions failed due to the exceptionally short and strong Si-H bonds. In the solid state, the Si-H units are not involved in any intermolecular interactions, but instead the crystal packing consists of exceptionally short and strong F...F interactions. The cohesive energies are entirely comprised of London dispersion interactions, similarly as in the crystal structures of noble gases
Contrasting partition behavior of F and Cl during hydrous mantle melting: implications for Cl/F signature in arc magmas
No full textInternational audienceWe present the results of five experiments on F and Cl partitioning during hydrous mantle melting under conditions relevant to subduction zone magmatism (1.2–2.5 GPa, 1,180°C–1,430°C). For each experiment, we determined the F and Cl partition coefficients between lherzolitic mineral phases (olivine, orthopyroxene (opx), clinopyroxene (cpx), and garnet), amphibole, and hydrous basaltic melts (0.2–5.9 wt.% dissolved H2O). At constant pressure, View MathML show contrasting response to the combined effects of decreasing temperature from 1,310°C to 1,180°C and increasing H2O content in the melt from 0.2 to 5.9 wt.%: View MathML. decreases from 0.123 ± 0.004 to 0.021 ± 0.014 while View MathML increases from 0.0021 ± 0.0031 to 0.07 ± 0.01. Similar results are observed for clinopyroxene: View MathML decreases from 0.153 ± 0.004 to 0.083 ± 0.004 while View MathML increases from 0.009 ± 0.0005 to 0.015 ± 0.0008. Experimentally determined F and Cl partition coefficients were used in a hydrous melting model of a lherzolitic mantle metasomatized by slab fluid. In this model, we vary the amount of metasomatic slab fluid added into the mantle while its composition is kept constant. Increasing the amount of fluid results in an increase of both the degree of melting (due to the effect of H2O addition) and the F and Cl input in the mantle wedge. Because of the change of F and Cl partition coefficients with the increase of H2O, the observed variation in the F and Cl contents of the modeled melts is produced not only by F and Cl input from the fluid, but also by the changes in F and Cl fractionation during hydrous melting. Overall, the model predicts that the Cl/F ratio of modeled melts increases with increasing fluid fraction. Therefore, a variation in the amount of fluid added to the mantle wedge can contribute to the variability in Cl/F ratios observed in arc melt inclusions
Cl, F, and SO2 in Central American volcanic gases
No full textThe Cl, F, SO2 contents and Cl/F and Cl/SO4 ratios in Central American volcanic gases are examined. 103−105 tons SO2 per day are given off during eruptions and 102 when a prominent vapor cloud persists between eruptive periods. Data regarding Cl and F and SO4 from leachates, condensates, and incrustations are compared. Our data suggest circumpacific volcanoes are SO2 poor relative to Cl and may be F poor although F is higher in basaltic Central American volcanoes than others
Halogen (F, Cl, Br, and I) Devolatilization During Prograde Subduction: Insights From Western Alps Ophiolites
No full textAbstract In order to examine the progressive chemical evolution of halogens (F, Cl, Br, I) in altered ocean crust (AOC) during prograde subduction, this study compares bulk and in situ halogen concentrations in mafic samples from three petrogenetically related exhumed terrains in the Western Alps (the Chenaillet ophiolite, the Queyras ophiolites of the Schistes Lustrés, and the Monviso ophiolite). Samples from the Chenaillet ophiolite represent oceanic crust unaffected by metamorphic halogen loss and define a protolith halogen content (122 μg/g F, 29 μg/g Cl, 82 ng/g Br, and 98 ng/g I). Samples from the Queyras ophiolites experienced blueschist facies conditions, undergoing recrystallization and halogen loss (74 μg/g F, 19 μg/g Cl, 70 ng/g Br, and 63 ng/g I). Eclogite facies samples from the Monviso meta‐ophiolite exhibit markedly reduced Cl (8 μg/g Cl) and Br (42 ng/g Br) contents relative to samples from Chenaillet and Queyras. Using electron probe microanalysis (EPMA), F and Cl host minerals (e.g., amphibole, chlorite, epidote) are identified and characterized in selected samples, showing a broad distribution of F and Cl, lending support to the view that halogen devolatilization in the subducting slab occurs continuously and is not dependent on the breakdown of a particular phase. In situ Cl concentrations decrease significantly between sub‐greenschist and blueschist assemblages. Fluorine is retained within subducting AOC and is decoupled from the heavy halogens (Cl, Br, I), which undergo continuous devolatilization during prograde metamorphism
Halogen (F, Cl, Br, and I) Devolatilization During Prograde Subduction: Insights From Western Alps Ophiolites
No full textIn order to examine the progressive chemical evolution of halogens (F, Cl, Br, I) in altered ocean crust (AOC) during prograde subduction, this study compares bulk and in situ halogen concentrations in mafic samples from three petrogenetically related exhumed terrains in the Western Alps (the Chenaillet ophiolite, the Queyras ophiolites of the Schistes Lustrés, and the Monviso ophiolite). Samples from the Chenaillet ophiolite represent oceanic crust unaffected by metamorphic halogen loss and define a protolith halogen content (122 μg/g F, 29 μg/g Cl, 82 ng/g Br, and 98 ng/g I). Samples from the Queyras ophiolites experienced blueschist facies conditions, undergoing recrystallization and halogen loss (74 μg/g F, 19 μg/g Cl, 70 ng/g Br, and 63 ng/g I). Eclogite facies samples from the Monviso meta-ophiolite exhibit markedly reduced Cl (8 μg/g Cl) and Br (42 ng/g Br) contents relative to samples from Chenaillet and Queyras. Using electron probe microanalysis (EPMA), F and Cl host minerals (e.g., amphibole, chlorite, epidote) are identified and characterized in selected samples, showing a broad distribution of F and Cl, lending support to the view that halogen devolatilization in the subducting slab occurs continuously and is not dependent on the breakdown of a particular phase. In situ Cl concentrations decrease significantly between sub-greenschist and blueschist assemblages. Fluorine is retained within subducting AOC and is decoupled from the heavy halogens (Cl, Br, I), which undergo continuous devolatilization during prograde metamorphism
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