Triphenylmethanol

Chembox new
Name = Triphenylmethanol
ImageFile1 = Triphenylmethanol.png ImageSize1 = 200px
ImageFile2 = Triphenylmethanol ball and stick.png ImageSize2 = 200px
ImageName1 = Triphenylmethanol
IUPACName = Triphenylmethanol
OtherNames = Triphenylcarbinol
Tritanol
Section1 = Chembox Identifiers
CASNo = 76-84-6
SMILES = OC(c2ccccc2)(c3ccccc3)c1ccccc1
Section2 = Chembox Properties
Formula = C₁₉H₁₆O
MolarMass = 260.32 g/mol
Density = 1.199 g/cm³
MeltingPt = 162 °C
BoilingPt = 360-380 °C
Section7 = Chembox Hazards
ExternalMSDS = [http://www.coleparmer.com/catalog/Msds/45870.htm External MSDS]
Section8 = Chembox Other
OtherCpds = Triphenylmethane

Triphenylmethanol (also known as triphenylcarbinol) is an aromatic 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 carbocation.

tructure and Properties

Triphenylmethanol contains three phenyl rings and a hydroxyl group bound to a central tetrahedral carbon atom. All three C-Ph bonds are typical of "sp"³-"sp"² carbon-carbon bonds with lengths of approximately 1.47 Å, while the C-O bond length is approximately 1.42 Å. ["Guidebook to Mechanism in Organic Chemistry", Sixth Edition, 1996, Peter Sykes, ISBN 0-58-244695-3]

Acidity and basicity

As triphenylmethanol is simply an alkyl-substituted derivative of methanol, its p"K"_a will be expected to lie somewhere in the range of 16-19. Typical of alcohols, resonance offers no stabilization of the conjugate base due to its being bonded to a saturated carbon atom. Furthermore, stabilization of the anion by solvation forces is largely ineffective due to the three bulky phenyl groups.

On the other hand, the basicity of triphenylmethanol is enhanced due to the formation of a stable carbocation upon breaking of the C-O bond. In a highly acid solution, the protonated form of triphenylmethanol will lose the equivalent of a water molecule to form the highly stable triphenylmethylium carbocation.

ynthesis

The preparation of triphenylmethanol from methyl benzoate or benzophenone and bromobenzene is a common laboratory experiment for teaching the Grignard reaction. [OrgSynth | author = W. E. Bachmann and H. P. Hetzner | title = Triphenylcarbinol | collvol = 3 | collvolpages = 839 | prep = cv3p0839] An alternative starting material is diethyl carbonate. ["The GC–MS Observation of Intermediates in a Stepwise Grignard Addition Reaction" Latimer, Devin. J. Chem. Educ. 2007, 84, 699. [http://jchemed.chem.wisc.edu/Journal/Issues/2007/Apr/abs699.html Link] ]

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