Gomberg's dimer

Gomberg's dimer is the organic compound with the formula Ph2C=C6H5-CPh3, where Ph = C6H5. It is a yellow solid that is air-stable for hours at room temperature and soluble in organic solvents.[1] The compound achieved fame as the dimer of triphenylmethyl radical, which was prepared by Moses Gomberg in his quest for hexaphenylethane.

Gomberg's dimer
Names
Preferred IUPAC name
1,1′,1′′-{[4-(Diphenylmethylidene)cyclohexa-2,5-dien-1-yl]methanetriyl}tribenzene
Other names
3-triphenylmethyl-6-diphenylmethylidene-1,4-cyclohexadiene
Identifiers
3D model (JSmol)
ChemSpider
  • InChI=1S/C38H30/c1-6-16-30(17-7-1)37(31-18-8-2-9-19-31)32-26-28-36(29-27-32)38(33-20-10-3-11-21-33,34-22-12-4-13-23-34)35-24-14-5-15-25-35/h1-29,36H
    Key: FWSYACUVHKGULL-UHFFFAOYSA-N
  • C1=CC=C(C=C1)C(=C2C=CC(C=C2)C(C3=CC=CC=C3)(C4=CC=CC=C4)C5=CC=CC=C5)C6=CC=CC=C6
Properties
C38H30
Molar mass 486.658 g·mol−1
Appearance Yellow solid
Density 1.16 g/cm3
Melting point 140–144 °C; 284–291 °F; 413–417 K
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Its quinoid structure has been determined by X-ray crystallography. The C-C bond that reversibly breaks is rather long at 159.7 picometers.[1]

Synthesis and reactions

Gomberg's dimer can be prepared quantitatively by treating trityl bromide with powdered copper or silver:[2]

2 Ph3CBr + 2 Cu → Ph2C=C6H5-CPh3 + 2 CuBr

Gomberg's dimer reversibly dissociates to the triphenylmethyl radical in organic solvents:[3]

See also

References
  1. Bochkarev, L. N.; Molosnova, N. E.; Zakharov, L. N.; Fukin, G. K.; Yanovsky, A. I.; Struchkov, Y. T. (1995). "1-Diphenylmethylene-4-(triphenylmethyl)cyclohexa-2,5-diene Benzene Solvate". Acta Crystallographica Section C Crystal Structure Communications. 51 (3): 489–491. doi:10.1107/S0108270194009005.
  2. Eisenberg, David C.; Lawrie, Christophe J. C.; Moody, Anne E.; Norton, Jack R. (1991). "Relative Rates of Hydrogen Atom (H.) Transfer from Transition-Metal Hydrides to Trityl Radicals". Journal of the American Chemical Society. 113 (13): 4888–4895. doi:10.1021/ja00013a026.
  3. Pangia, Thomas M.; Davies, Casey G.; Prendergast, Joshua R.; Gordon, Jesse B.; Siegler, Maxime A.; Jameson, Guy N. L.; Goldberg, David P. (28 March 2018). "Observation of Radical Rebound in a Mononuclear Nonheme Iron Model Complex". Journal of the American Chemical Society. 140 (12): 4191–4194. doi:10.1021/jacs.7b12707. PMC 6047074. PMID 29537258.
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