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IUPAC name
Other names
519-73-3 YesY
ChemSpider 10169 YesY
EC number 208-275-0
Jmol-3D images Image
PubChem 10614
Molar mass 244.33 g/mol
Appearance Colorless solid
Density 1.014 g/cm3
Melting point 92 to 94 °C (198 to 201 °F; 365 to 367 K)
Boiling point 359 °C (678 °F; 632 K)
Solubility soluble in dioxane[1] and hexane
Acidity (pKa) 33
Safety data sheet External MSDS
R-phrases R36 R37 R38
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

Triphenylmethane, or triphenyl methane, is the hydrocarbon with the formula (C6H5)3CH. This colorless solid is soluble in nonpolar organic solvents and not in water. Triphenylmethane is 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.


Triphenylmethane can be synthesized by Friedel-Crafts reaction from benzene and chloroform with aluminium chloride catalyst:

3 C6H6 + CHCl3 → Ph3CH + 3 HCl

Alternatively, benzene may react with carbon tetrachloride using the same catalyst to obtain the trityl chloride-aluminium chloride adduct, which is hydrolyzed with dilute acid:[2]

3 C6H6 + CCl4 + AlCl3 → Ph3CCl·AlCl3
Ph3CCl·AlCl3 + HCl → Ph3CH

Synthesis from benzylidene chloride, prepared from benzaldehyde and phosphorus pentachloride, is used as well.


The pKa of the hydrogen on the central carbon is 33.[3] Triphenylmethane is significantly more acidic than most other hydrocarbons because the trityl anion is stabilized by extensive delocalization over three phenyl rings. However, delocalization does not occur simultaneously over all phenyl rings due to steric effects: each phenyl ring forces the other two out of coplanarity to form a three-vaned fan, such that delocalization only occurs if the p-orbital of the anionic carbon is parallel to the p-orbitals of one of the 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:[4]

(C6H5)3CCl + 2 Na → (C6H5)3CNa + NaCl

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

Triarylmethane dyes[edit]

Main article: Triarylmethane dye

Examples of triarylmethane dyes are bromocresol green:

Bromocresol green

And the nitrogen bearing malachite green:

Malachite green

See also[edit]


  1. ^
  2. ^ J. F. Norris (1941). "Triphenylmethane". Org. Synth. ; Coll. Vol. 1, p. 548 
  3. ^ Ronald Breslow and William Chu (1969). "Electrochemical determinations of p Ka's. Triphenylmethanes and cycloheptatriene". Journal of the American Chemical Society 92 (7): 2165. doi:10.1021/ja00710a077. 
  4. ^ W. B. Renfrow Jr and C. R. Hauser (1943). "Triphenylmethylsodium". Org. Synth. ; Coll. Vol. 2, p. 607