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Tetramethylammonium Pentafluoroxenate
Tetramethylammonium pentafluoroxenate is the chemical compound with the formula N(CH3)4XeF5. The ion it contains was the first example of a pentagonal planar molecular geometry AX5E2 species. It was prepared by the reaction of N(CH3)4F with xenon tetrafluoride, N(CH3)4F being chosen because it can be prepared in anhydrous form and is readily soluble in organic solvents. The anion is planar, with the fluorine atoms in a slightly distorted pentagonal coordination (Xe–F bond lengths 197.9–203.4 pm, and F–X–F bond angles 71.5°–72.3°). Other salts have been prepared with sodium, cesium and rubidium, and vibrational spectra show that these contain the same planar ion. The isolated anion has the point group In geometry, a point group is a mathematical group of symmetry operations (isometries in a Euclidean space) that have a fixed point in common. The coordinate origin of the Euclidean space is conventionally taken to be a fixed point, and every p ... of ''D''5h. ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Pentagonal Planar Molecular Geometry
In chemistry, the pentagonal planar molecular geometry describes the shape of compounds where five atoms, groups of atoms, or ligands are arranged around a central atom, defining the vertices of a pentagon. Examples The only two pentagonal planar species known are the isoelectronic (nine valence electrons) ions and . Both are derived from the pentagonal bipyramid In geometry, the pentagonal bipyramid (or dipyramid) is third of the infinite set of face-transitive bipyramids, and the 13th Johnson solid (). Each bipyramid is the dual of a uniform prism. Although it is face-transitive, it is not a Plat ... with two lone pairs occupying the apical positions and the five fluorine atoms all equatorial. References {{MolecularGeometry Stereochemistry Molecular geometry ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
VSEPR Theory
Valence shell electron pair repulsion (VSEPR) theory ( , ), is a model used in chemistry to predict the geometry of individual molecules from the number of electron pairs surrounding their central atoms. It is also named the Gillespie-Nyholm theory after its two main developers, Ronald Gillespie and Ronald Nyholm. The premise of VSEPR is that the valence electron pairs surrounding an atom tend to repel each other and will, therefore, adopt an arrangement that minimizes this repulsion. This in turn decreases the molecule's energy and increases its stability, which determines the molecular geometry. Gillespie has emphasized that the electron-electron repulsion due to the Pauli exclusion principle is more important in determining molecular geometry than the electrostatic repulsion. The insights of VSEPR theory are derived from topological analysis of the electron density of molecules. Such quantum chemical topology (QCT) methods include the electron localization function (ELF) and ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Journal Of The American Chemical Society
The ''Journal of the American Chemical Society'' is a weekly peer-reviewed scientific journal that was established in 1879 by the American Chemical Society. The journal has absorbed two other publications in its history, the ''Journal of Analytical and Applied Chemistry'' (July 1893) and the ''American Chemical Journal'' (January 1914). It covers all fields of chemistry. Since 2021, the editor-in-chief is Erick M. Carreira (ETH Zurich). In 2014, the journal moved to a hybrid open access publishing model. Abstracting and indexing The journal is abstracted and indexed in Chemical Abstracts Service, Scopus, EBSCO databases, ProQuest databases, Index Medicus/MEDLINE/PubMed, and the Science Citation Index Expanded. According to the ''Journal Citation Reports'', the journal has a 2021 impact factor of 16.383. Editors-in-chief The following people are or have been editor-in-chief: * 1879–1880 – Hermann Endemann * 1880–1881 – Gideon E. Moore * 1881–1882 – Hermann Endemann ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Tetramethylammonium Fluoride
Tetramethylammonium fluoride is the quaternary ammonium salt with the formula (CH3)4NF. This hygroscopic white solid is a source of “naked fluoride", that is fluoride ions not connected to a metal atom in a complex. Most other soluble salts of fluoride are in fact bifluorides, HF2–. Historically, there has been two main approaches to prepare TMAF: (i) Via neutralization of tetramethylammonium hydroxide (TMAOH) with HF, and (ii) through the metathesis reaction of different ammonium salts with inorganic sources of fluoride, such as KF or CsF. Due to the high basicity of the fluoride anion, the salt reacts slowly with acetonitrile, inducing its dimerization to CH3C(NH2)=CHCN, which co-crystallizes. Related salts * Tetramethylphosphonium fluoride (CH3)4PF forms stable solutions in acetonitrile. It is prepared by reaction of the ylide with potassium bifluoride: :(CH3)3P=CH2 + KHF2 → (CH3)4PF + KF :In the gas phase, tetramethylphosphonium fluoride exists as the phosphoran ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenon Tetrafluoride
Xenon tetrafluoride is a chemical compound with chemical formula . It was the first discovered binary compound of a noble gas. It is produced by the chemical reaction of xenon with fluorine: : Xe + 2 → This reaction is exothermic, releasing an energy of 251 kJ/mol. Xenon tetrafluoride is a colorless crystalline solid that sublimes at 117 °C. Its structure was determined by both NMR spectroscopy and X-ray crystallography in 1963. The structure is square planar, as has been confirmed by neutron diffraction studies. According to VSEPR theory, in addition to four fluoride ligands, the xenon center has two lone pairs of electrons. These lone pairs are mutually ''trans''. Synthesis Xenon tetrafluoride is produced by heating a mixture of xenon and fluorine in a 1:5 molar ratio in a nickel container to 400 °C. Some xenon difluoride () and xenon hexafluoride () is also produced, where increased temperature or decreased fluorine concentration in the input ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Molecular Symmetry
Molecular symmetry in chemistry describes the symmetry present in molecules and the classification of these molecules according to their symmetry. Molecular symmetry is a fundamental concept in chemistry, as it can be used to predict or explain many of a molecule's chemical properties, such as whether or not it has a dipole moment, as well as its allowed spectroscopic transitions. To do this it is necessary to use group theory. This involves classifying the states of the molecule using the irreducible representations from the character table of the symmetry group of the molecule. Symmetry is useful in the study of molecular orbitals, with applications to the Hückel method, to ligand field theory, and to the Woodward-Hoffmann rules. Many university level textbooks on physical chemistry, quantum chemistry, spectroscopy and inorganic chemistry discuss symmetry. Another framework on a larger scale is the use of crystal systems to describe crystallographic symmetry in bulk materia ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Fluoro Complexes
Fluorine is a chemical element with the symbol F and atomic number 9. It is the lightest halogen and exists at standard conditions as a highly toxic, pale yellow diatomic gas. As the most electronegative reactive element, it is extremely reactive, as it reacts with all other elements except for the light inert gases. Among the elements, fluorine ranks 24th in universal abundance and 13th in terrestrial abundance. Fluorite, the primary mineral source of fluorine which gave the element its name, was first described in 1529; as it was added to metal ores to lower their melting points for smelting, the Latin verb meaning 'flow' gave the mineral its name. Proposed as an element in 1810, fluorine proved difficult and dangerous to separate from its compounds, and several early experimenters died or sustained injuries from their attempts. Only in 1886 did French chemist Henri Moissan isolate elemental fluorine using low-temperature electrolysis, a process still employed for modern produc ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Xenon(IV) Compounds
Xenon is a chemical element with the symbol Xe and atomic number 54. It is a dense, colorless, odorless noble gas found in Earth's atmosphere in trace amounts. Although generally unreactive, it can undergo a few chemical reactions such as the formation of xenon hexafluoroplatinate, the first noble gas compound to be synthesized. Xenon is used in flash lamps and arc lamps, and as a general anesthetic. The first excimer laser design used a xenon dimer molecule (Xe2) as the lasing medium, and the earliest laser designs used xenon flash lamps as pumps. Xenon is also used to search for hypothetical weakly interacting massive particles and as a propellant for ion thrusters in spacecraft. Naturally occurring xenon consists of seven stable isotopes and two long-lived radioactive isotopes. More than 40 unstable xenon isotopes undergo radioactive decay, and the isotope ratios of xenon are an important tool for studying the early history of the Solar System. Radioactive xenon-135 is pro ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
