Triphenylmethane

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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 ?)

Triphenylmethane or triphenyl methane (sometimes also known as Tritan), 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 Dutch 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 Ph3C-H bond is relatively weak, with a bond dissociation energy (BDE) of 81 kcal/mol, or about 24 kcal/mol less than methane. [4] Correspondingly, triphenylmethane is mildly acidic, with a pKa of 33.3. [5]

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 isolable in crown ethers...

TriphenylmethaneAnion.png

...and the sodium salt can also be prepared from the chloride: [6]

(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 unmodified anion is red, and can be used as an indicator in acid–base titrations. Derived substances have proven useful as chemical dyes.

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

<span class="mw-page-title-main">Phenyl group</span> Cyclic chemical group (–C₆H₅)

In organic chemistry, the phenyl group, or phenyl ring, is a cyclic group of atoms with the formula C6H5, and is often represented by the symbol Ph. The phenyl group is 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. A phenyl group has 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, the phenyl group is chemically aromatic and has equal bond lengths between carbon atoms in the ring.

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. Both proceed by electrophilic aromatic substitution.

In organic chemistry, an aryl halide is an aromatic compound in which one or more hydrogen atoms, directly bonded to an aromatic ring are replaced by a halide. The haloarene are different from haloalkanes because they exhibit many differences in methods of preparation and properties. The most important members are the aryl chlorides, but the class of compounds is so broad that there are many derivatives and applications.

<span class="mw-page-title-main">Aluminium chloride</span> Chemical compound

Aluminium chloride, also known as aluminium trichloride, is an inorganic compound with the formula AlCl3. It forms a hexahydrate with the formula [Al(H2O)6]Cl3, containing six water molecules of hydration. Both the anhydrous form and the hexahydrate are colourless crystals, but samples are often contaminated with iron(III) chloride, giving them a yellow colour.

<span class="mw-page-title-main">Chromium(III) chloride</span> Chemical compound

Chromium(III) chloride (also called chromic chloride) is an inorganic chemical compound with the chemical formula CrCl3. It forms several hydrates with the formula CrCl3·nH2O, among which are hydrates where n can be 5 (chromium(III) chloride pentahydrate CrCl3·5H2O) or 6 (chromium(III) chloride hexahydrate CrCl3·6H2O). The anhydrous compound with the formula CrCl3 are violet crystals, while the most common form of the chromium(III) chloride are the dark green crystals of hexahydrate, CrCl3·6H2O. Chromium chlorides find use as catalysts and as precursors to dyes for wool.

<span class="mw-page-title-main">Benzoyl chloride</span> Organochlorine compound (C7H5ClO)

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, and consists of a benzene ring with an acyl chloride substituent. 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.

<span class="mw-page-title-main">Aromatic sulfonation</span> Chemical reaction which replaces a hydrogen on an arene with sulfonic acid, –NH–SO3H

In organic chemistry, aromatic sulfonation is an organic reaction in which a hydrogen atom on an arene is replaced by a sulfonic acid functional group in an electrophilic aromatic substitution. Aryl sulfonic acids are used as detergents, dye, and drugs.

<span class="mw-page-title-main">Diazonium compound</span> Group of organonitrogen compounds

Diazonium compounds or diazonium salts are a group of organic compounds sharing a common functional group [R−N+≡N]X where R can be any organic group, such as an alkyl or an aryl, and X is an inorganic or organic anion, such as a halide.

(<i>E</i>)-Stilbene Chemical compound

(E)-Stilbene, commonly known as trans-stilbene, is an organic compound represented by the condensed structural formula C6H5CH=CHC6H5. Classified as a diarylethene, it features a central ethylene moiety with one phenyl group substituent on each end of the carbon–carbon double bond. It has an (E) stereochemistry, meaning that the phenyl groups are located on opposite sides of the double bond, the opposite of its geometric isomer, cis-stilbene. Trans-stilbene occurs as a white crystalline solid at room temperature and is highly soluble in organic solvents. It can be converted to cis-stilbene photochemically, and further reacted to produce phenanthrene.

<span class="mw-page-title-main">Triphenylmethanol</span> 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.

<span class="mw-page-title-main">Triphenylmethyl radical</span> Chemical compound

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 trityl radical has been heavily exploited.

<span class="mw-page-title-main">Diphenylmethane</span> 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.

<span class="mw-page-title-main">Dewar benzene</span> Chemical compound

Dewar benzene (also spelled dewarbenzene) or bicyclo[2.2.0]hexa-2,5-diene is a bicyclic isomer of benzene with the molecular formula C6H6. The compound is named after James Dewar who included this structure in a list of possible C6H6 structures in 1869. However, he did not propose it as the structure of benzene, and in fact he supported the correct structure previously proposed by August Kekulé in 1865.

<span class="mw-page-title-main">Benzenediazonium tetrafluoroborate</span> 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.

<span class="mw-page-title-main">Triphenylmethyl chloride</span> 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.

<span class="mw-page-title-main">Sulfenyl chloride</span> Chemical group (R–S–Cl)

In organosulfur chemistry, a sulfenyl chloride is a functional group with the connectivity R−S−Cl, where R is alkyl or aryl. Sulfenyl chlorides are reactive compounds that behave as sources of RS+. They are used in the formation of RS−N and RS−O bonds. According to IUPAC nomenclature they are named as alkyl thiohypochlorites, i.e. esters of thiohypochlorous acid.

<span class="mw-page-title-main">Triphenylmethyl hexafluorophosphate</span> Chemical compound

Triphenylmethyl hexafluorophosphate is an organic salt with the formula [(C6H5)3C]+[PF6], consisting of the triphenylcarbenium cation [(C6H5)3C]+ and the hexafluorophosphate anion [PF6].

<span class="mw-page-title-main">2-Phenylpyridine</span> Chemical compound

2-Phenylpyridine is an organic compound with the formula C6H5C5H4N (or C11H9N). It is a colourless viscous liquid. The compound and related derivatives have attracted interest as precursors to highly fluorescent metal complexes of possible value as organic light emitting diodes (OLEDs).

<span class="mw-page-title-main">Pentanoyl chloride</span> Chemical compound

Pentanoyl chloride is an acyl chloride derived from pentanoic acid. It is a colorless liquid that is used to attach the valeroyl group. It is usually produced by chlorination of valeric acid.

<span class="mw-page-title-main">Triphenylcarbenium</span>

In chemistry, triphenylcarbenium, triphenylmethyl cation, tritylium , or trityl cation is an ion with formula [C19H15]+ or (C6H5)3C+, consisting of a carbon atom with a positive charge connected to three phenyl groups. It is a charged version of the triphenylmethyl radical (C6H5)3C•. 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. 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.
  5. 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.
  6. W. B. Renfrow Jr and C. R. Hauser (1943). "Triphenylmethylsodium". Organic Syntheses ; Collected Volumes, vol. 2, p. 607.
  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. Bibcode:1994AcCrC..50.1362G. doi:10.1107/S0108270194004439.