Trifluorotoluene

Chembox new
Name = Trifluorotoluene
ImageFileL1 = benzotrifluoride.png ImageSizeL1=160px
ImageFileR1 = Trifluorotoluene-3D-balls.png ImageSizeR1 = 120
OtherNames = Benzotrifluoride
α,α,α-Trifluorotoluene
Section1 = Chembox Identifiers
CASNo = 98-08-8
Section2 = Chembox Properties
Formula = C₆H₅CF₃
MolarMass = 146.11 g/mol
Appearance = colorless liquid
Density = 1.19 g/mL at 20 °C
MeltingPt = -29 °C
BoilingPt = 102 °C

Trifluorotoluene is an organic compound with the formula of C₆H₅CF₃. This colorless fluorocarbon is used as a specialty solvent in organic synthesis and an intermediate in the production of pesticides and pharmaceuticals.Banks, R.E. Organofluorine Chemicals and their Industrial Applications, Ellis Horwood LTD, Chichester, 1979.]

ynthesis

For small-scale laboratory preparations, trifluorotoluene is synthesized by coupling an aromatic halide and trifluoromethyl iodide in the presence of a copper catalyst: [Ogawa, Akiya; Tsuchii, Kaname “α,α,α-Trifluorotoluene” in Encyclopedia of Reagents for Organic Synthesis 2005, John Wiley and Sons. DOI| 10.1002/047084289X.rn00653] :ArX + CF₃I → Ar-CF₃ + CuXI (where X = I, Br, Cl)

For large scale preparations using batch or continuous processes, benzotrichloride is treated with hydrogen fluoride under a pressure.Siegemund, Günter “Aromatic Compounds with Fluorinated Side-Chains” in Ullmann’s Encyclopedia of Industrial Chemistry 2005, Wiley-VCH. DOI|10.1002/14356007.a11_349.] :C₆H₅CCl₃ + 3 HF → C₆H₅CF₃ + 3 HCl

Uses

Trifluorotoluene has a variety of niche uses.

olvent alternative to dichloromethane

According to Ogawa and Curran, trifluorotoluene is similar to dichloromethane in standard acylation, tosylation, and silylation reactions. [Ogawa, Akiya; Curran, Dennis P. “Benzotrifluoride: A Useful Alternative Solvent for Organic Reactions Currently Conducted in Dichloromethane and Related Solvents” Journal of Organic Chemistry 1997, volume 62, pp. 450-451. DOI|10.1021/jo9620324] The dielectric constants for dichloromethane and trifluorotoluene are 9.04 and 9.18, respectively, indicative similar solvating properties. Dipole moments compare less favorably: 1.89 and 2.86 D for dichloromethane and trifluorotoluene, respectively. Replacing dichloromethane is advantageous when conditions require higher boiling solvents since trifluorotoluene boils 62 °C higher than dichoromethane (b.p. 40 °C).

As a solvent, trifluorotoluene is useful in mild Lewis-acid catalyzed reactions, such as the Friedel-Crafts preparations. The most common catalyst, aluminium trichloride reacts with trifluorotoluene at room temperature, however zinc chloride however does not.

ynthetic intermediate

A second and perhaps more valuable use of trifluorotoluene is as a synthetic intermediate. A derivative of trifluorotoluene, 3-aminobenzotrifluoride, is the precursor to the herbicide fluometuron, 1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea. It is synthesized via nitration followed by reduction to meta-H₂NC₆H₄CF₃. This aniline is then converted to the urea.

Flumetramide (6- [4-(trifluoromethyl)phenyl] morpholin-3-one), a skeletal muscle relaxant, is also prepared from trifluorotoluene.

References