Triphenylmethane

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Triphenylmethane

IUPAC name	Triphenylmethane
Other names	1,1',1"-Methylidynetrisbenzene
Identifiers
CAS number	[519-73-3]
EINECS number	208-275-0
SMILES	c1ccccc1C(c2ccccc2)c3ccccc3
Properties
Molecular formula	C₁₉H₁₆
Molar mass	244.33 g/mol
Density	1.014 g/cm³
Melting point	92-94 °C
Boiling point	359 °C
Solubility in water	insoluble
Hazards
MSDS	External MSDS
R-phrases	R36 R37 R38
Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa) Infobox disclaimer and references

Triphenylmethane, or triphenyl methane, is the hydrocarbon with the formula (C₆H₅)₃CH. This colorless solid is soluble in nonpolar organic solvents, but not water. Triphenylmethane has the basic skeleton of many synthetic dyes called triarylmethane dyes, many of them are pH indicators, and some display fluorescence. A trityl group in organic chemistry is a triphenylmethyl group Ph₃C, e.g. triphenylmethyl chloride — trityl chloride.

1 Preparation
2 Acidity
3 Triarylmethane dyes
4 References

[edit] Preparation

Triphenylmethane can be synthesized by Friedel-Crafts reaction from benzene and chloroform with aluminium chloride catalyst. Synthesis from benzylidene chloride, prepared from benzaldehyde and phosphorus pentachloride, is used as well.

[edit] Acidity

The pKa of the hydrogen on the central carbon is around 31. Triphenylmethane is significantly more acidic than most other hydrocarbons because the planar trityl anion is stabilized by extensive delocalization over three phenyl rings. The trityl anion absorbs strongly in the visible region, making it red. This colour can be used as an indicator when maintaining anhydrous conditions with calcium hydride; the hydride reagent reacts with water to form solid calcium hydroxide, while it is also a strong enough base to generate the trityl anion. If the hydride is used up then the solution will turn colourless. The sodium salt can be prepared also from the chloride:^[1]

(C₆H₅)₃CCl + 2 Na → (C₆H₅)₃CNa + NaCl

Before the popularization of butyllithium and related strong bases, trityl sodium was often used as a strong, non-nucleophilic base.