Triphenylmethane

Last updated
Triphenylmethane
Triphenylmethan.svg
Triphenylmethane-3D-balls.png
Names
Preferred IUPAC name
1,1′,1′′-Methanetriyltribenzene
Other names
Triphenylmethane
1,1′,1′′-Methylidynetrisbenzene
Identifiers
3D model (JSmol)
ChEBI
ChemSpider
ECHA InfoCard 100.007.524 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 208-275-0
PubChem CID
UNII
  • InChI=1S/C19H16/c1-4-10-16(11-5-1)19(17-12-6-2-7-13-17)18-14-8-3-9-15-18/h1-15,19H Yes check.svgY
    Key: AAAQKTZKLRYKHR-UHFFFAOYSA-N Yes check.svgY
  • InChI=1/C19H16/c1-4-10-16(11-5-1)19(17-12-6-2-7-13-17)18-14-8-3-9-15-18/h1-15,19H
    Key: AAAQKTZKLRYKHR-UHFFFAOYAF
  • c1c(cccc1)C(c2ccccc2)c3ccccc3
Properties
C19H16
Molar mass 244.337 g·mol−1
AppearanceColorless 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)
Insoluble
Solubility Soluble in dioxane [1] and hexane
Acidity (pKa)33.3
−165.6×10−6 cm3/mol
Hazards
GHS labelling:
GHS-pictogram-exclam.svg
Warning
H315, H319, H335
Safety data sheet (SDS) External MSDS
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
X mark.svgN  verify  (what is  Yes check.svgYX mark.svgN ?)
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) and the triphenylmethyl radical (trityl radical).

Contents

Preparation

Triphenylmethane was first synthesized in 1872 by the German chemist August Kekulé and his Belgian student Antoine Paul Nicolas Franchimont (1844–1919) by heating diphenylmercury (Hg(C6H5)2, Quecksilberdiphenyl) with benzal chloride (C6H5CHCl2, Benzylenchlorid). [2]

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 triphenylmethyl chloridealuminium chloride adduct, which is hydrolyzed with dilute acid: [3]

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

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

Reactions of C-H bond

The pKa is 33.3. [4] Triphenylmethane is significantly more acidic than most other hydrocarbons because the charge is delocalized over three phenyl rings. Steric effects however prevent all three phenyl rings from achieving coplanarity simultaneously. Consequently diphenylmethane 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 titrations.

The sodium salt can be prepared also from the chloride: [5]

(C6H5)3CCl + 2 Na → (C6H5)3CNa + NaCl

The use of tritylsodium as a strong, non-nucleophilic base has been eclipsed by the popularization of butyllithium and related strong bases.

The Ph3C-H bond is relatively weak, with a bond dissociation energy (BDE) of 81 kcal/mol. By contrast, the BDE for methane is 105 kcal/mol. [6]

Triarylmethane dyes

Examples of triarylmethane dyes are bromocresol green:

Bromocresol green.svg

And the nitrogen-bearing malachite green:

Malachite green structure.svg

Trityl group

Protecting group

The triphenylmethyl substituent, also called trityl, is widely used in organic chemistry. Trityl serves as a protecting group for alcohols. [7]

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). [8]

See also

Related Research Articles

Phenyl group Cyclic group of atoms with the formula C6H5

In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula C6H5. Phenyl groups are closely related to benzene and can be viewed as a benzene ring, minus a hydrogen, which may be replaced by some other element or compound to serve as a functional group. Phenyl groups have six carbon atoms bonded together in a hexagonal planar ring, five of which are bonded to individual hydrogen atoms, with the remaining carbon bonded to a substituent. Phenyl groups are commonplace in organic chemistry. Although often depicted with alternating double and single bonds, phenyl groups are chemically aromatic and have equal bond lengths between carbon atoms in the ring.

Chromium(III) chloride Chemical compound

Chromium(III) chloride (also called chromic chloride) describes any of several compounds with the formula CrCl3 · xH2O, where x can be 0, 5, and 6. The anhydrous compound with the formula CrCl3 is a violet solid. The most common form of the trichloride is the dark green hexahydrate, CrCl3 · 6 H2O. Chromium chlorides find use as catalysts and as precursors to dyes for wool.

Oxalyl chloride Chemical compound

Oxalyl chloride is a chemical compound with the formula (COCl)2. This colorless, sharp-smelling liquid, the diacyl chloride of oxalic acid, is a useful reagent in organic synthesis.

Benzoyl chloride Chemical compound

Benzoyl chloride, also known as benzenecarbonyl chloride, is an organochlorine compound with the formula C7H5ClO. It is a colourless, fuming liquid with an irritating odour. It is mainly useful for the production of peroxides but is generally useful in other areas such as in the preparation of dyes, perfumes, pharmaceuticals, and resins.

Phosphorus pentachloride Chemical compound

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 moisture-sensitive solid, although commercial samples can be yellowish and contaminated with hydrogen chloride.

Dichlorocarbene is the reactive intermediate with chemical formula CCl2. Although this chemical species has not been isolated, it is a common intermediate in organic chemistry, being generated from chloroform. This bent diamagnetic molecule rapidly inserts into other bonds.

Carbenium ion

A carbenium ion is a positive ion with the structure RR′R″C+, that is, a chemical species with a trivalent carbon that bears a +1 formal charge.

Triphenylmethanol Chemical compound

Triphenylmethanol is an organic compound. It is a white crystalline solid that is insoluble in water and petroleum ether, but well soluble in ethanol, diethyl ether, and benzene. In strongly acidic solutions, it produces an intensely yellow color, due to the formation of a stable "trityl" carbocation. Many derivatives of triphenylmethanol are important dyes.

Triphenylmethyl radical Chemical compound

The triphenylmethyl radical is a persistent radical and the first radical ever described in organic chemistry.

Iodobenzene Chemical compound

Iodobenzene is an organoiodine compound consisting of a benzene ring substituted with one iodine atom. It is useful as a synthetic intermediate in organic chemistry. It is a volatile colorless liquid, although aged samples appear yellowish.

Diphenylmethane Chemical compound

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

A reaction intermediate or an intermediate is a molecular entity that is formed from the reactants and reacts further to give the directly observed products of a chemical reaction. Most chemical reactions are stepwise, that is they take more than one elementary step to complete. An intermediate is the reaction product of each of these steps, except for the last one, which forms the final product. Reactive intermediates are usually short lived and are very seldom isolated. Also, owing to the short lifetime, they do not remain in the product mixture.

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.

Bis(triphenylphosphine)iminium chloride Chemical compound

Bis(triphenylphosphine)iminium chloride is the chemical compound with the formula [(C6H5)3P)2N]Cl, often written [(Ph3P)2N]Cl and abbreviated [PPN]Cl or [PNP]Cl. This colorless salt is a source of the PPN+ cation, which is used as an unreactive and weakly coordinating cation to isolate reactive anions. PPN+ is a phosphazene.

Triarylmethane dyes are synthetic organic compounds containing triphenylmethane backbones. As dyes, these compounds are intensely colored. They are produced industrially as dyes.

Sodium tetraphenylborate Chemical compound

Sodium tetraphenylborate is the organic compound with the formula NaB(C6H5)4. It is a salt, wherein the anion consists of four phenyl rings bonded to boron. This white crystalline solid is used to prepare other tetraphenylborate salts, which are often highly soluble in organic solvents. The compound is used in inorganic and organometallic chemistry as a precipitating agent for potassium, ammonium, rubidium, and cesium ions, and some organic nitrogen compounds.

Benzenediazonium tetrafluoroborate Organic compound containing an –N≡N+ function

Benzenediazonium tetrafluoroborate is an organic compound with the formula [C6H5N2]BF4. It is a salt of a diazonium cation and tetrafluoroborate. It exists as a colourless solid that is soluble in polar solvents. It is the parent member of the aryldiazonium compounds, which are widely used in organic chemistry.

Triphenylmethyl chloride Chemical compound

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.

Triphenylmethyl hexafluorophosphate Chemical compound

Triphenylmethyl hexafluorophosphate is an organic salt with the formula C
19
H
15
F
6
P
or (C
6
H
5
)
3
CPF
6
, consisting of the triphenylmethyl cation [(C
6
H
5
)
3
C]+
and the hexafluorophosphate anion] [PF
6
]
. The cation is also called triphenylcarbenium, trityl cation, or tritylium.

Triphenylcarbenium

In chemistry, triphenylcarbenium, triphenylmethyl cation, tritylium , or trityl cation is an ion with formula [C
19
H
15
]+
or (C
6
H
5
)
3
C+
, consisting of a carbon atom with a positive charge connected to three phenyl groups. It is a charged version of the triphenylmethyl radical (C
6
H
5
)
3
C
. The name is often abbreviated to triphenylmethyl or trityl in salts, although these names also denote the chemical group in compounds like triphenylmethyl chloride that do not contain the cation.

References

  1. "Triphenylmethane | 519-73-3".
  2. Aug. Kekulé and A. Franchimont (1872) "Ueber das Triphenylmethan" (On triphenylmethane), Berichte der deutschen chemischen Gesellschaft, 5 : 906–908.
  3. J. F. Norris (1925). "Triphenylmethane". Organic Syntheses. 4: 81. doi:10.15227/orgsyn.004.0081.
  4. Ronald Breslow and William Chu (1969). "Electrochemical determinations of pKa's. Triphenylmethanes and cycloheptatriene". Journal of the American Chemical Society. 92 (7): 2165. doi:10.1021/ja00710a077.
  5. W. B. Renfrow Jr and C. R. Hauser (1943). "Triphenylmethylsodium". Organic Syntheses .; Collective Volume, vol. 2, p. 607
  6. Xue, Xiao-Song; Ji, Pengju; Zhou, Biying; Cheng, Jin-Pei (2017). "The Essential Role of Bond Energetics in C–H Activation/Functionalization". Chemical Reviews. 117 (13): 8622–8648. doi:10.1021/acs.chemrev.6b00664. PMID   28281752.
  7. Delbert D. Reynolds, William Lloyd Evans (1942). "β-d-Glucose-1,2,3,4-Tetraacetate". Organic Syntheses. 22: 56. doi:10.15227/orgsyn.022.0056.
  8. Glidewell, C.; Ferguson, G. (1994). "Molecules isoelectronic with 2,2,2-triphenylethanol: Multiple Hydrogen-Bonding Modes in the Structures of O-Tritylhydroxylamine, Ph3CONH2, and Triphenylmethanesulfenamide, Ph3CSNH2". Acta Crystallographica Section C Crystal Structure Communications. 50 (8): 1362–1366. doi:10.1107/S0108270194004439.