The triphenylmethyl radical (often shorted to trityl radical) is an organic compound with the formula (C6H5)3C. It is a persistent radical. It was the first radical ever to be described in organic chemistry. Because of its accessibility, the trityl radical has been heavily exploited.[1]
Solutions containing the radical are yellow; when the temperature of the solution is raised, the yellow color becomes more intense as the equilibrium is shifted in favor of the radical (in accordance with Le Chatelier's principle).
When exposed to air, the radical rapidly oxidizes to the peroxide, and the color of the solution changes from yellow to colorless. Likewise, the radical reacts with iodine to triphenylmethyl iodide.
While the trityl radical forms a quinoid dimer, derivatives thereof with the appropriate substitution pattern do form dimers with a hexaphenylethane structure. X-ray studies give a bond length of 1.67 Å for hexakis(3,5-di-t-butylphenyl)ethane. Theoretical calculations on a very high level of theory indicate that van der Waals attraction between the tert-butyl groups create a potential minimum that is absent in the unsubstituted molecule.[3][4] Other derivatives have been reported as the quinoid dimer [5]
History
The radical was discovered by Moses Gomberg in 1900 at the University of Michigan.[6][7][8] He tried to prepare hexaphenylethane from triphenylmethyl chloride and zinc in benzene in a Wurtz reaction and found that the product, based on its behaviour towards iodine and oxygen, was far more reactive than anticipated. The discovered structure was used in the development of ESR spectroscopy and confirmed by it.[9][10][11]
The correct quinoid structure for the dimer was suggested as early as 1904 but this structure was soon after abandoned by the scientific community in favor of hexaphenylethane (4).[12] It subsequently took until 1968 for its rediscovery when researchers at the Vrije Universiteit Amsterdam published proton NMR data.[13]
^Tidwell, Thomas T. (2010). "Triarylmethyl and Related Radicals". Stable Radicals. pp. 1–31. doi:10.1002/9780470666975.ch1. ISBN9780470666975.
^Smith, Michael B.; March, Jerry (2007), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (6th ed.), New York: Wiley-Interscience, ISBN978-0-471-72091-1
^Grimme, Stefan; Schreiner, Peter R. (2011). "Steric crowding can stabilize a labile molecule: Solving the hexaphenylethane riddle". Angewandte Chemie International Edition. 50 (52): 12639–12642. doi:10.1002/anie.201103615. PMID 22025456.
^Uchimura, Y.; Takeda, T.; Katoono, R.; Fujiwara, K.; Suzuki, T. (2015). "New Insights into the Hexaphenylethane Riddle: Formation of an α,o-Dimer". Angewandte Chemie International Edition. 54 (13): 4010–4013. doi:10.1002/anie.201500122. PMID 25704856.
^Gomberg, M. (1901). "On trivalent carbon". Journal of the American Chemical Society. 23 (7): 496–502. doi:10.1021/ja02033a015. (Note: radical is also called a cadicle.)
^Gomberg, M. (1902). "On trivalent carbon". Journal of the American Chemical Society. 24 (7): 597–628. doi:10.1021/ja02021a001.
^Weissman, S. I.; Sowden, John C. (1953). "Electron distribution in triphenylmethyl: Hyperfine structure of the paramagnetic resonance absorption of (C6H5)3C13*". Journal of the American Chemical Society. 75 (2): 503. doi:10.1021/ja01098a522.
^Sinclair, J.; Kivelson, D. (1968). "Electron spin resonance studies of substituted triphenylmethyl radicals". Journal of the American Chemical Society. 90 (19): 5074–5080. doi:10.1021/ja01021a004.
^"ESR spectrum of the triphenylmethyl radical". School of Chemistry, University of Bristol. Retrieved August 5, 2018.
^McBride, J. M. (1974). "The hexaphenylethane riddle". Tetrahedron. 30 (14): 2009–2022. doi:10.1016/S0040-4020(01)97332-6.
^Lankamp, H.; Nauta, W. Th.; MacLean, C. (1968). "A new interpretation of the monomer–dimer equilibrium of triphenylmethyl- and alkyl-substituted-diphenyl methyl-radicals in solution". Tetrahedron Letters. 9 (2): 249–254. doi:10.1016/S0040-4039(00)75598-5.
External links
Molecule of the Month, June 1997
Triphenylmethyl radical : properties and synthesis
February 07, 2023
triphenylmethyl, radical, triphenylmethyl, radical, often, shorted, trityl, radical, organic, compound, with, formula, c6h5, persistent, radical, first, radical, ever, described, organic, chemistry, because, accessibility, trityl, radical, been, heavily, explo. The triphenylmethyl radical often shorted to trityl radical is an organic compound with the formula C6H5 3C It is a persistent radical It was the first radical ever to be described in organic chemistry Because of its accessibility the trityl radical has been heavily exploited 1 Triphenylmethyl radical NamesPreferred IUPAC name TriphenylmethylIdentifiersCAS Number 2216 49 1 N3D model JSmol Interactive imageInteractive imageChemSpider 10627185 YPubChem CID 5374035InChI InChI 1S C19H15 c1 4 10 16 11 5 1 19 17 12 6 2 7 13 17 18 14 8 3 9 15 18 h1 15H YKey OHSJPLSEQNCRLW UHFFFAOYSA N YSMILES c1ccc cc1 C c1ccccc1 c1ccccc1C1 CC C C C1 C C1 CC CC C1 C1 CC CC C1PropertiesChemical formula C 19H 15Molar mass 243 329 g mol 1Except where otherwise noted data are given for materials in their standard state at 25 C 77 F 100 kPa Y verify what is Y N Infobox references Contents 1 Preparation and properties 2 History 3 See also 4 References 5 External linksPreparation and properties EditIt can be prepared by homolysis of triphenylmethyl chloride 1 by a metal like silver or zinc in benzene or diethyl ether The radical 2 forms a chemical equilibrium with the quinoid type dimer 3 Gomberg s dimer In benzene the concentration of the radical is 2 2 Solutions containing the radical are yellow when the temperature of the solution is raised the yellow color becomes more intense as the equilibrium is shifted in favor of the radical in accordance with Le Chatelier s principle When exposed to air the radical rapidly oxidizes to the peroxide and the color of the solution changes from yellow to colorless Likewise the radical reacts with iodine to triphenylmethyl iodide While the trityl radical forms a quinoid dimer derivatives thereof with the appropriate substitution pattern do form dimers with a hexaphenylethane structure X ray studies give a bond length of 1 67 A for hexakis 3 5 di t butylphenyl ethane Theoretical calculations on a very high level of theory indicate that van der Waals attraction between the tert butyl groups create a potential minimum that is absent in the unsubstituted molecule 3 4 Other derivatives have been reported as the quinoid dimer 5 History EditThe radical was discovered by Moses Gomberg in 1900 at the University of Michigan 6 7 8 He tried to prepare hexaphenylethane from triphenylmethyl chloride and zinc in benzene in a Wurtz reaction and found that the product based on its behaviour towards iodine and oxygen was far more reactive than anticipated The discovered structure was used in the development of ESR spectroscopy and confirmed by it 9 10 11 The correct quinoid structure for the dimer was suggested as early as 1904 but this structure was soon after abandoned by the scientific community in favor of hexaphenylethane 4 12 It subsequently took until 1968 for its rediscovery when researchers at the Vrije Universiteit Amsterdam published proton NMR data 13 See also EditTriphenylmethyl hexafluorophosphate Triphenylmethane Triarylmethane dye Trivalent group 14 radicalsReferences Edit Tidwell Thomas T 2010 Triarylmethyl and Related Radicals Stable Radicals pp 1 31 doi 10 1002 9780470666975 ch1 ISBN 9780470666975 Smith Michael B March Jerry 2007 Advanced Organic Chemistry Reactions Mechanisms and Structure 6th ed New York Wiley Interscience ISBN 978 0 471 72091 1 Lewars Errol 2008 8 Hexaphenylethane Modeling Marvels Springer Bibcode 2008moma book L Grimme Stefan Schreiner Peter R 2011 Steric crowding can stabilize a labile molecule Solving the hexaphenylethane riddle Angewandte Chemie International Edition 50 52 12639 12642 doi 10 1002 anie 201103615 PMID 22025456 Uchimura Y Takeda T Katoono R Fujiwara K Suzuki T 2015 New Insights into the Hexaphenylethane Riddle Formation of an a o Dimer Angewandte Chemie International Edition 54 13 4010 4013 doi 10 1002 anie 201500122 PMID 25704856 Gomberg M 1900 An instance of trivalent carbon triphenylmethyl Journal of the American Chemical Society 22 11 757 771 doi 10 1021 ja02049a006 Gomberg M 1901 On trivalent carbon Journal of the American Chemical Society 23 7 496 502 doi 10 1021 ja02033a015 Note radical is also called a cadicle Gomberg M 1902 On trivalent carbon Journal of the American Chemical Society 24 7 597 628 doi 10 1021 ja02021a001 Weissman S I Sowden John C 1953 Electron distribution in triphenylmethyl Hyperfine structure of the paramagnetic resonance absorption of C6H5 3C13 Journal of the American Chemical Society 75 2 503 doi 10 1021 ja01098a522 Sinclair J Kivelson D 1968 Electron spin resonance studies of substituted triphenylmethyl radicals Journal of the American Chemical Society 90 19 5074 5080 doi 10 1021 ja01021a004 ESR spectrum of the triphenylmethyl radical School of Chemistry University of Bristol Retrieved August 5 2018 McBride J M 1974 The hexaphenylethane riddle Tetrahedron 30 14 2009 2022 doi 10 1016 S0040 4020 01 97332 6 Lankamp H Nauta W Th MacLean C 1968 A new interpretation of the monomer dimer equilibrium of triphenylmethyl and alkyl substituted diphenyl methyl radicals in solution Tetrahedron Letters 9 2 249 254 doi 10 1016 S0040 4039 00 75598 5 External links EditMolecule of the Month June 1997 Triphenylmethyl radical properties and synthesis Retrieved from https en wikipedia org w index php title Triphenylmethyl radical amp oldid 1132849403, wikipedia, wiki, book, books, library,
