organic chemistry Organic chemistry is a subdiscipline within chemistry involving the scientific study of the structure, properties, and reactions of organic compounds and organic materials, i.e., matter in its various forms that contain carbon atoms.Clayden, J.; ...

, methenium (also called methylium, carbenium, methyl cation, or protonated methylene) is a

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

with the formula . It can be viewed as a

methylene radical Methylene (systematically named methylidene and dihydridocarbon; also called carbene) is an organic compound with the chemical formula (also written ). It is a colourless gas that fluoresces in the mid-infrared range, and only persists in dilut ...

(:) with an added

proton A proton is a stable subatomic particle, symbol , H+, or 1H+ with a positive electric charge of +1 ''e'' elementary charge. Its mass is slightly less than that of a neutron and 1,836 times the mass of an electron (the proton–electron mass ...

(), or as a

methyl radical Methyl (also systematically named trihydridocarbon) is an organic compound with the chemical formula (also written as •). It is a metastable colourless gas, which is mainly produced ''in situ'' as a precursor to other hydrocarbons in the petrol ...

(•) with one

electron The electron ( or ) is a subatomic particle with a negative one elementary electric charge. Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no kn ...

removed. It is a

carbocation A carbocation is an ion with a positively charged carbon atom. Among the simplest examples are the methenium , methanium and vinyl cations. Occasionally, carbocations that bear more than one positively charged carbon atom are also encountere ...

and an

enium ion In chemistry, an onium ion is a cation formally obtained by the protonation of mononuclear parent hydride of a pnictogen (group 15 of the periodic table), chalcogen (group 16), or halogen (group 17). The oldest-known onium ion, and the namesake f ...

, making it the simplest of the

carbenium ion A carbenium ion is a positive ion with the structure RR′R″C+, that is, a chemical species with a trivalent carbon that bears a +1 formal charge. In older literature the name carbonium ion was used for this class, but now it refers exclusivel ...

Structure

Experiments and calculations generally agree that the methenium ion is planar, with threefold

symmetry Symmetry (from grc, συμμετρία "agreement in dimensions, due proportion, arrangement") in everyday language refers to a sense of harmonious and beautiful proportion and balance. In mathematics, "symmetry" has a more precise definit ...

. The carbon atom is a prototypical (and exact) example of sp² hybridization.

Preparation and reactions

For

mass spectrometry Mass spectrometry (MS) is an analytical technique that is used to measure the mass-to-charge ratio of ions. The results are presented as a ''mass spectrum'', a plot of intensity as a function of the mass-to-charge ratio. Mass spectrometry is use ...

studies at low pressure, methenium can be obtained by

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nanometer, nm (with a corresponding frequency around 30 Hertz, PHz) to 400 nm (750 Hertz, THz), shorter than that of visible light, but longer than ...

photoionization Photoionization is the physical process in which an ion is formed from the interaction of a photon with an atom or molecule. Cross section Not every interaction between a photon and an atom, or molecule, will result in photoionization. The prob ...

of methyl radical, or by collisions of monatomic cations such as and with neutral methane. In such conditions, it will react with

acetonitrile Acetonitrile, often abbreviated MeCN (methyl cyanide), is the chemical compound with the formula and structure . This colourless liquid is the simplest organic nitrile (hydrogen cyanide is a simpler nitrile, but the cyanide anion is not clas ...

to form the ion . Upon capture of a low-energy electron (less than ), it will spontaneously dissociate. It is seldom encountered as an intermediate in the condensed phase. It is proposed as a reactive intermediate that forms upon protonation or hydride abstraction of methane with FSO₃H-SbF₅. The methenium ion is very reactive, even towards

alkane In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which ...

References

{{Reflist, refs= {{cite journal , last=Bahati , first=E. M. , last2=Fogle , first2=M. , last3=Vane , first3=C. R. , last4=Bannister , first4=M. E. , last5=Thomas , first5=R. D. , last6=Zhaunerchyk , first6=V. , title=Electron-impact dissociation of {{chem, CD, 3, + and {{chem, CH, 3, + ions producing {{chem, CD, 2, +, {{chem, CH, + and {{chem, C, + fragment ions , journal=Physical Review A , publisher=American Physical Society (APS) , volume=79 , issue=5 , date=2009-05-11 , issn=1050-2947 , doi=10.1103/physreva.79.052703 , page=052703 {{cite journal , last=McEwan , first=Murray J. , last2=Denison , first2=Arthur B. , last3=Huntress , first3=Wesley T. , last4=Anicich , first4=Vincent G. , last5=Snodgrass , first5=J. , last6=Bowers , first6=M. T. , title=Association reactions at low pressure. 2. The methylium/methyl cyanide system , journal=The Journal of Physical Chemistry , publisher=American Chemical Society (ACS) , volume=93 , issue=10 , year=1989 , issn=0022-3654 , doi=10.1021/j100347a039 , pages=4064–4068 {{cite journal , last=Sharma , first=R. B. , last2=Semo , first2=N. M. , last3=Koski , first3=W. S. , title=Dynamics of the reactions of methylium, methylene radical cation, and methyliumylidene with acetylene , journal=The Journal of Physical Chemistry , publisher=American Chemical Society (ACS) , volume=91 , issue=15 , year=1987 , issn=0022-3654 , doi=10.1021/j100299a037 , pages=4127–4131 {{cite journal , last=Golob , first=L. , last2=Jonathan , first2=N. , last3=Morris , first3=A. , last4=Okuda , first4=M. , last5=Ross , first5=K.J. , title=The first ionization potential of the methyl radical as determined by photoelectron spectroscopy , journal=Journal of Electron Spectroscopy and Related Phenomena , publisher=Elsevier BV , volume=1 , issue=5 , year=1972 , issn=0368-2048 , doi=10.1016/0368-2048(72)80022-7 , pages=506–508 Carbocations Ions Organic chemistry

Structure

Preparation and reactions

See also

References