Triphenylmethane, or triphenyl methane, is the

hydrocarbon In organic chemistry, a hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic, and their odors are usually weak or ex ...

with the

formula In science, a formula is a concise way of expressing information symbolically, as in a mathematical formula or a ''chemical formula''. The informal use of the term ''formula'' in science refers to the general construct of a relationship betwee ...

(C₆H₅)₃CH. This colorless solid is soluble in nonpolar organic solvents and not in water. Triphenylmethane is the basic skeleton of many synthetic

dye A dye is a colored substance that chemically bonds to the substrate to which it is being applied. This distinguishes dyes from pigments which do not chemically bind to the material they color. Dye is generally applied in an aqueous solution an ...

s called

triarylmethane dye Triarylmethane dyes are synthetic organic compounds containing triphenylmethane backbones. As dyes, these compounds are intensely colored. They are produced industrially as dyes. Families Triarylmethane dyes can be grouped into families accordin ...

s, many of them are

pH indicator A pH indicator is a halochromic chemical compound added in small amounts to a solution so the pH (acidity or basicity) of the solution can be determined visually or spectroscopically by changes in absorption and/or emission properties. Hence, ...

s, and some display

fluorescence Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and therefore a lower photon energy, tha ...

. A trityl group in organic chemistry is a triphenylmethyl group Ph₃C, e.g.

triphenylmethyl chloride Triphenylmethyl chloride or trityl chloride (TrCl) is a white solid with the chemical formula C19H15Cl. It is an alkyl halide, sometimes used to introduce the trityl protecting group. Preparation Triphenylmethyl chloride is commercially available ...

(trityl chloride) and the

triphenylmethyl radical The triphenylmethyl radical (often shorted to trityl radical) is an organic compound with the formula (C6H5)3C. It is a persistent radical. It was the first radical ever to be described in organic chemistry. Because of its accessibility, the tri ...

(trityl radical).

Preparation

Triphenylmethane was first synthesized in 1872 by the German chemist

August Kekulé Friedrich August Kekulé, later Friedrich August Kekule von Stradonitz ( , ; 7 September 1829 – 13 July 1896), was a German organic chemist. From the 1850s until his death, Kekulé was one of the most prominent chemists in Europe, especially ...

and his Belgian student Antoine Paul Nicolas Franchimont (1844–1919) by heating

diphenylmercury Diphenylmercury is the organomercury compound with the formula Hg(C6H5)2. It is a white solid. The compound is of historic interest as a particularly stable organometallic compound but it finds few uses because of its high toxicity. Preparation C ...

(Hg(C₆H₅)₂, ''Quecksilberdiphenyl'') with

benzal chloride Benzal chloride is an organic compound with the formula C6H5CHCl2. This colourless liquid is a lachrymator and is used as a building block in organic synthesis. Preparation and usage Benzal chloride is produced by the free radical chlorination o ...

(C₆H₅CHCl₂, ''Benzylenchlorid''). Triphenylmethane can be synthesized by

Friedel–Crafts reaction The Friedel–Crafts reactions are a set of reactions developed by Charles Friedel and James Crafts in 1877 to attach substituents to an aromatic ring. Friedel–Crafts reactions are of two main types: alkylation reactions and acylation reactions ...

from

benzene Benzene is an organic chemical compound with the molecular formula C6H6. The benzene molecule is composed of six carbon atoms joined in a planar ring with one hydrogen atom attached to each. Because it contains only carbon and hydrogen atoms, ...

and

chloroform Chloroform, or trichloromethane, is an organic compound with chemical formula, formula Carbon, CHydrogen, HChlorine, Cl3 and a common organic solvent. It is a colorless, strong-smelling, dense liquid produced on a large scale as a precursor to ...

with

aluminium chloride Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula . It forms hexahydrate with the formula , containing six water molecules of hydration. Both are colourless crystals, but samples are often contam ...

catalyst Catalysis () is the process of increasing the rate of a chemical reaction by adding a substance known as a catalyst (). Catalysts are not consumed in the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recyc ...

: :3 C₆H₆ + CHCl₃ → Ph₃CH + 3 HCl Alternatively, benzene may react with

carbon tetrachloride Carbon tetrachloride, also known by many other names (such as tetrachloromethane, also IUPAC nomenclature of inorganic chemistry, recognised by the IUPAC, carbon tet in the cleaning industry, Halon-104 in firefighting, and Refrigerant-10 in HVAC ...

using the same catalyst to obtain the

–

adduct, which is hydrolyzed with dilute acid: :3 C₆H₆ + CCl₄ + AlCl₃ → Ph₃CCl·AlCl₃ :Ph₃CCl·AlCl₃ + HCl → Ph₃CH Synthesis from

benzylidene chloride Benzal chloride is an organic compound with the formula C6H5CHCl2. This colourless liquid is a lachrymator and is used as a building block in organic synthesis. Preparation and usage Benzal chloride is produced by the free radical chlorination o ...

, prepared from

benzaldehyde Benzaldehyde (C6H5CHO) is an organic compound consisting of a benzene ring with a formyl substituent. It is the simplest aromatic aldehyde and one of the most industrially useful. It is a colorless liquid with a characteristic almond-like odor. ...

and

phosphorus pentachloride Phosphorus pentachloride is the chemical compound with the formula PCl5. It is one of the most important phosphorus chlorides, others being PCl3 and POCl3. PCl5 finds use as a chlorinating reagent. It is a colourless, water-sensitive and moist ...

, is used as well.

Reactions of C-H bond

The p''K''_a is 33.3. Triphenylmethane is significantly more acidic than most other hydrocarbons because the charge is

delocalized In chemistry, delocalized electrons are electrons in a molecule, ion or solid metal that are not associated with a single atom or a covalent bond.IUPAC Gold Boo''delocalization''/ref> The term delocalization is general and can have slightly diff ...

over three phenyl rings. Steric effects however prevent all three phenyl rings from achieving coplanarity simultaneously. Consequently

diphenylmethane Diphenylmethane is an organic compound with the formula (C6H5)2CH2 (often abbreviated ). The compound consists of methane wherein two hydrogen atoms are replaced by two phenyl groups. It is a white solid. Diphenylmethane is a common skeleton in or ...

is even more acidic, because in its anion the charge is spread over two phenyl rings at the same time. The trityl anion is red. This colour can be used as an indicator in

acid–base titration An acid–base titration is a method of quantitative analysis for determining the concentration of an acid or base by exactly neutralizing it with a standard solution of base or acid having known concentration. A pH indicator is used to monitor ...

s. The sodium salt can be prepared also from the chloride: :(C₆H₅)₃CCl + 2 Na → (C₆H₅)₃CNa + NaCl The use of tritylsodium as a strong,

non-nucleophilic base As the name suggests, a non-nucleophilic base is a sterically hindered organic base that is a poor nucleophile. Normal bases are also nucleophiles, but often chemists seek the proton-removing ability of a base without any other functions. Typic ...

has been eclipsed by the popularization of

butyllithium Butyllithium may refer to one of 5 isomeric organolithium reagents of which 3 are commonly used in chemical synthesis: * ''n''-Butyllithium, abbreviated BuLi or nBuLi * ''sec''-Butyllithium, abbreviated ''sec''-BuLi or sBuLi, has 2 stereoisomers, ...

and related strong bases. The Ph₃C-H bond is relatively weak, with a

bond dissociation energy The bond-dissociation energy (BDE, ''D''0, or ''DH°'') is one measure of the strength of a chemical bond . It can be defined as the standard enthalpy change when is cleaved by homolysis to give fragments A and B, which are usually radical s ...

(BDE) of 81 kcal/mol. By contrast, the BDE for methane is 105 kcal/mol.

Triarylmethane dyes

Examples of triarylmethane dyes are

bromocresol green Bromocresol green (BCG) is a dye of the triphenylmethane family (triarylmethane dyes). It belongs to a class of dyes called sulfonephthaleins. It is used as a pH indicator in applications such as growth mediums for microorganisms and titrations. ...

: :

And the

nitrogen Nitrogen is the chemical element with the symbol N and atomic number 7. Nitrogen is a nonmetal and the lightest member of group 15 of the periodic table, often called the pnictogens. It is a common element in the universe, estimated at se ...

-bearing

malachite green Malachite green is an organic compound that is used as a dyestuff and controversially as an antimicrobial in aquaculture. Malachite green is traditionally used as a dye for materials such as silk, leather, and paper. Despite its name the dye is ...

: :

Trityl group

Protecting group

The triphenylmethyl substituent, also called trityl, is widely used in organic chemistry. Trityl serves as a

protecting group A protecting group or protective group is introduced into a molecule by chemical modification of a functional group to obtain chemoselectivity in a subsequent chemical reaction. It plays an important role in multistep organic synthesis. In many ...

for alcohols. : protection (requires proton acceptor): Ph₃CCl + ROH → Ph₃COR + HCl : deprotection: Ph₃COR + HBr → ROH + Ph₃CBr

Platform for unusual functional groups

Trityl derivatives of reactive functional groups are often crystalline and in some cases sterically stabilized relative to less bulky derivatives. Three such derivatives are ''S''-nitrosotriphenylmethanethiol (Ph₃CSNO), tritylsulfenyl chloride (Ph₃CSCl), and trityl sulfenamide (Ph₃CSNH₂).

References

{{Reflist Aromatic hydrocarbons Phenyl compounds