Tetraphenylmethane

Tetraphenylmethane is an organic compound consisting of a methane core with four phenyl substituents. It was first synthesized by Moses Gomberg in 1898.

Tetraphenylmethane
Names
IUPAC name
Tetraphenylmethane
Identifiers
3D model (JSmol)
ChemSpider
ECHA InfoCard 100.010.132
Properties
C25H20
Molar mass 320.44 g/mol
Melting point 272 °C (522 °F; 545 K)
Structure[1]
tetragonal
P421c, No. 114
S4
a = 10.896 Å, c = 7.280 Å
(20 °C)
2
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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Infobox references

Synthesis

Gomberg's classical organic synthesis shown below starts by reacting triphenylmethyl bromide 1 with phenylhydrazine 2 to the hydrazine 3. Oxidation with nitrous acid then produces the azo compound 4 from which on heating above the melting point, nitrogen gas evolves with formation of tetraphenylmethane 5.[2]

Gomberg was able to distinguish this compound from triphenylmethane (elemental analysis was not an option given the small differences in the hydrogen fractions of 6.29% and 6.60%) by nitration of 5 with nitric acid to 6. A strong base would be able to abstract the methine proton of the nitrated triphenylmethyl compound if present, forming a strongly colored compound.

He obtained further evidence for the formation of tetraphenylmethane by reducing the nitro groups to amino groups with zinc dust in acetic acid to the leuco dye 7, which on exposure to hydrochloric acid eliminates aniline to the known compound pararosaniline 8.

Gomberg's success in synthesizing tetraphenylmethane set him on the attempt to prepare the next homologue hexaphenylethane, which led him to the discovery of the triphenylmethyl radical.

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See also

References
  1. Robbins, A.; Jeffrey, G. A.; Chesick, J. P.; Donohue, J.; Cotton, F. A.; Frenz, B. A.; Murillo, C. A. (1975-10-01). "A refinement of the crystal structure of tetraphenylmethane: three independent redeterminations". Acta Crystallographica Section B Structural Crystallography and Crystal Chemistry. 31 (10): 2395–2399. doi:10.1107/S0567740875007686. ISSN 0567-7408.
  2. Gomberg, M. (1898). "On tetraphenylmethane". J. Am. Chem. Soc. 20 (10): 773–780. doi:10.1021/ja02072a009.
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