true methanium: Interactive image fluxional methanium: Interactive image true methanium: InChI=1S/CH5/h1H5/q+1 Key: PXOFOHGGCICFQD-UHFFFAOYSA-N fluxional methanium: InChI=1S/CH5/c1-2/h2H,1H3/q+1 Key: AJLDAZFHECSILY-UHFFFAOYSA-N true methanium: [C+H5] fluxional methanium: [CH3+].[HH] In chemistry , methanium is a complex positive ion with formula [ C H 5 ] + ( metastable transitional form, a carbon atom covalently bonded to five hydrogen atoms) or [ CH 3 (H 2 )] + (fluxional form, namely a molecule with one carbon atom covalently bonded to three hydrogen atoms and one dihydrogen molecule), bearing a +1 electric charge . It is a superacid and one of the onium ions , indeed the simplest carbonium ion . It is highly unstable and highly reactive even upon having a complete octet, thus granting its superacidic properties. Methanium can be produced in the laboratory as a rarefied gas or as a dilute species in superacids. It was prepared for the first time in 1950 and published in 1952 by Victor Talrose and his assistant Anna Konstantinovna Lyubimova. [ 2 ] [ 3 ] It occurs as an intermediate species in chemical reactions. The methanium ion is named after methane ( CH 4 ), by analogy with the derivation of ammonium ion ( NH + 4 ) from ammonia ( NH 3 ). Fluxional methanium can be visualised as a CH + 3 carbenium ion with a molecule of hydrogen interacting with the empty orbital in a 3-center-2-electron bond . The bonding electron pair in the H 2 molecule is shared between the two hydrogen and one carbon atoms making up the 3-center-2-electron bond. [ 4 ] The two hydrogen atoms in the H 2 molecule can continuously exchange positions with the three hydrogen atoms in the CH + 3 ion (a conformation change called pseudorotation , specifically the Berry mechanism ). The methanium ion is therefore considered a fluxional molecule . The energy barrier for the exchange is quite low and occurs even at very low temperatures. [ 5 ] [ 6 ] Infrared spectroscopy has been used to obtain information about the different conformations of the methanium ion. [ 7 ] [ 8 ] [ 9 ] The IR spectrum of plain methane has two C-H bands from symmetric and asymmetric stretching at around 3000 cm −1 and two bands around 1400 cm −1 from symmetrical and asymmetric bending vibrations. In the spectrum of CH + 5 three asymmetric stretching vibrations are present around 2800–3000 cm −1 , a rocking vibration at 1300 cm −1 , and a bending vibration at 1100 1300 cm −1 . Methanium can be prepared from methane by the action of very strong acids, such as fluoroantimonic acid ( antimony pentafluoride SbF 5 in hydrogen fluoride HF). [ 10 ] At about 270 Pa of pressure and ambient temperature, the methane ion CH + 4 will react with neutral methane to yield methanium and a methyl radical : [ 11 ] The methanium ion can also be made in the gas phase via the reaction of methane and an H + ion (i.e. a proton). [ citation needed ] Stability and reactions The cations obtained by reaction of methane with SbF 5 + HF , including methanium, are stabilized by interactions with the HF molecules. At low pressures (around 1 mmHg) and ambient temperatures, methanium is unreactive towards neutral methane. [ 11 ] Further reading D. W. Boo; Z. F. Liu; A. G. Suits; J. S. Tse; Y. T. Lee (1995). "Dynamics of Carbonium Ions Solvated by Molecular Hydrogen: CH5+(H2)n (n= 1, 2, 3)". Science . 269 (5220): 57– 9. Bibcode : 1995Sci...269...57B . doi : 10.1126/science.269.5220.57 . PMID 17787703 . S2CID 2100896 . Kramer, G. M. (1999). "CH5+ Stability and Mass Spectrometry" . Science . 286 (5442): 1051a–1051. doi : 10.1126/science.286.5442.1051a . ISSN 0036-8075 . Marx, D. (1999). "MOLECULAR SPECTROSCOPY:CH5+: The Cheshire Cat Smiles". Science . 284 (5411): 59– 61. Bibcode : 1999Sci...284...59. . doi : 10.1126/science.284.5411.59 . ISSN 0036-8075 . S2CID 94058015 . Xiao-Gang Wang; Tucker Carrington Jr (2016). "Calculated rotation-bending energy levels of CH 5 + and a comparison with experiment". Journal of Chemical Physics . 144 (20): 204304. Bibcode : 2016JChPh.144t4304W . doi : 10.1063/1.4948549 . PMID 27250303 .

H. Schmiedt; Per Jensen; S. Schlemmer (2017). "Rotation-vibration motion of extremely flexible molecules - The molecular superrotor" . Chemical Physics Letters . 672 : 34– 46. Bibcode : 2017CPL...672...34S . doi : 10.1016/j.cplett.2017.01.045 . ↑ Chemistry, International Union of Pure and Applied (2009). "carbonium ion" . IUPAC Compendium of Chemical Terminology . IUPAC. doi : 10.1351/goldbook.C00839 . ISBN 978-0-9678550-9-7 . Retrieved 27 November 2018 . ↑ V. L. Talrose and A. K. Lyubimova, Dokl. Akad. Nauk SSSR 86, 909-912 (1952) (In Russian: Тальрозе, В. Л., and А. К. Любимова. "Вторичные процессы в ионном источнике масс-спектрометра." ДАН СССР 86 (1952): 909-912) ↑ Nikolaev, Eugene (1998). "Victor Talrose: an appreciation" . Journal of Mass Spectrometry . 33 (6): 499– 501. Bibcode : 1998JMSp...33..499N . doi : 10.1002/(SICI)1096-9888(199806)33:6 < 499::AID-JMS684 > 3.0.CO ; 2-C . ISSN 1076-5174 . ↑ Rasul, Golam; Prakash, G.K. Surya; Olah, George A. (2011). "Comparative study of the hypercoordinate carbonium ions and their boron analogs: A challenge for spectroscopists". Chemical Physics Letters . 517 ( 1– 3): 1– 8. Bibcode : 2011CPL...517....1R . doi : 10.1016/j.cplett.2011.10.020 . ↑ Schreiner, Peter R.; Kim, Seung-Joon; Schaefer, Henry F.; von Ragué Schleyer, Paul (1993). " CH + 5 : The never-ending story or the final word?". Journal of Chemical Physics . 99 (5): 3716– 3720. doi : 10.1063/1.466147 . ↑ Müller, Hendrik; Kutzelnigg, Werner; Noga, Jozef; Klopper, Wim (1997). "CH5+: The story goes on. An explicitly correlated coupled-cluster study". Journal of Chemical Physics . 106 (5): 1863. Bibcode : 1997JChPh.106.1863M . doi : 10.1063/1.473340 . ↑ White, Edmund T.; Tang, Jian; Oka, Takeshi (1999). " CH + 5 : The infrared spectrum observed". Science . 284 (5411): 135– 7. Bibcode : 1999Sci...284..135W . doi : 10.1126/science.284.5411.135 . PMID 10102811 . ↑ Oskar Asvany, Padma Kumar P; Redlich, Britta; Hegemann, Ilka; Schlemmer, Stephan; Marx, Dominik (2005). "Understanding the infrared spectrum of bare CH + 5 " . Science . 309 (5738): 1219– 1222. Bibcode : 2005Sci...309.1219A . doi : 10.1126/science.1113729 . PMID 15994376 . S2CID 28745636 . ↑ Huang, Xinchuan; McCoy, Anne B.; Bowman, Joel M. ; Johnson, Lindsay M.; Savage, Chandra; Dong, Feng; Nesbitt, David J. (2006). "Quantum deconstruction of the infrared spectrum of CH + 5 " . Science . 311 (5757): 60– 63. Bibcode : 2006Sci...311...60H . doi : 10.1126/science.1121166 . PMID 16400143 . S2CID 26158108 . ↑ Sommer, J.; Jost, R. (2000). "Carbenium and carbonium ions in liquid- and solid-superacid-catalyzed activation of small alkanes" (PDF) . Pure and Applied Chemistry . 72 (12): 2309– 2318. doi : 10.1351/pac200072122309 . S2CID 46627813 . 1 2 Field, F. H.; Munson, M. S. B. (1965). "Reactions of gaseous ions. XIV. Mass spectrometric studies of methane at pressures to 2 Torr". Journal of the American Chemical Society . 87 (15): 3289– 3294. doi : 10.1021/ja01093a001 . Articles with short description Short description is different from Wikidata Chemical articles with multiple compound IDs Multiple chemicals in an infobox that need indexing Chemical articles without CAS registry number Chemical pages without ChemSpiderID Articles without EBI source Articles without KEGG source Articles without UNII source Articles containing unverified chemical infoboxes Short description matches Wikidata All articles with unsourced statements Articles with unsourced statements from November 2022