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
CAS Number	18909-18-7
3D model (JSmol)	Interactive image
ChemSpider	123721
PubChem CID	140290
CompTox Dashboard (EPA)	DTXSID10894912
InChI 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
SMILES 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
Chemical formula	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

• Hexaphenylethane