A halonium ion in organic chemistry is any onium ion containing a bridged halogen atom carrying a positive charge. This cation has the general structure R-X⁺-R where X is any halogen and R any organic residue and this structure can be cyclic or an open chain molecular structure. Organic chemistry is a specific discipline within chemistry which involves the scientific study of the structure, properties, composition, reactions, and preparation (by synthesis or by other means) of chemical compounds consisting of primarily carbon and hydrogen, which may contain any number of other elements, including nitrogen, oxygen, halogens as well... The halogens are a chemical series of nonmetals. ... A cation is an ion with positive charge. ...

Halonium ions were first postulated in 1937 by Roberts and Kimball ^[1] to account for observed diastereoselectivity in halogenation of alkenes. They correctly argued that if the initial reaction intermediate in bromination is the open-chain X^--C-C⁺, rotation around the C-C single bond would be possible leading to a mixture of equal amounts of dihalogen cis isomer and trans isomer which is not the case. They also asserted that a positively charged halogen atom is isoelectronic with oxygen and that carbon and bromine have comparable ionization potentials. Diastereomers are stereoisomers that are not enantiomers or mirror images of each other. ... Halogenation is a chemical reaction that replaces a hydrogen atom with a halogen atom. ... The chemical structure of ethylene, the simplest alkene. ... Covalently bonded hydrogen and carbon in a molecule of methane. ... In chemistry, geometric isomerism is a form of stereoisomerism and describes the orientation of functional groups at the ends of a bond around which no rotation is possible. ... Two or more molecular entities (atoms, molecules, ions) are described as isoelectronic if they have the same number of valence electrons and the same structure (number and connectivity of atoms), but may differ in the elements involved. ... The ionization potential, or ionization energy, of an atom or molecule is the energy required to strip it of an electron. ...

In 1970 George A. Olah succeeded in preparing and isolating halonium salts ^[2] by adding a methyl halide such as methyl bromide or methyl chloride in sulfur dioxide at -78°C to a complex of antimony pentafluoride and tetrafluoromethane in sulfur dioxide. After evaporation of sulfur dioxide this procedure left crystals of CH₃-X⁺-CH₃SbF₆^-, stable at room temperature but not to moisture. George Andrew Olah (born 1927) is a U.S. (Hungarian-born) chemist. ... A magnified crystal of a salt (halite/sodium chloride) Salt covering the floor of Bad Water in Death Valley, CA, the lowest point in the US. A salt, in chemistry, is any ionic compound composed of cations (positively charged ions) and anions (negative ions) so that the product is neutral... The chemical compound bromomethane is an organic halogen compound with formula BrCH3. ... Chloromethane or Methyl chloride is a chemical compound once widely used as a refrigerant. ... Sulfur dioxide (or Sulphur dioxide) has the chemical formula SO2. ... Antimony pentafluoride, SbF5 is a chemical compound. ... Carbon tetrafluoride, CF4, is a carbon fluoride. ... Room temperature describes a certain temperature within enclosed space that is uses for various purposes by human beings. ...

References

1. ↑  The Halogenation of Ethylenes Irving Roberts, George E. Kimball J. Am. Chem. Soc.; 1937; 59(5); 947-948. Abstract
2. ↑  Friedel-Crafts chemistry. V. Isolation, carbon-13 nuclear magnetic resonance, and laser Raman spectroscopic study of dimethylhalonium fluoroantimonates George A. Olah, John R. DeMember J. Am. Chem. Soc.; 1970; 92(3); 718-720. Abstract