Trifluoromethanol

Trifluoromethanol is a synthetic organic compound with the formula CF₃OH.^[1] It is also referred to as perfluoromethanol or trifluoromethyl alcohol. The compound is the simplest perfluoroalcohol.^[2] The substance is a colorless gas, which is unstable at room temperature.

Trifluoromethanol

Names
Preferred IUPAC name Trifluoromethanol
Other names Trifluoromethyl alcohol, perfluoromethanol
Identifiers
CAS Number	1493-11-4
3D model (JSmol)	Interactive image
ChemSpider	66527
PubChem CID	73894
CompTox Dashboard (EPA)	DTXSID30896817 DTXSID00164217, DTXSID30896817
InChI InChI=1S/CHF3O/c2-1(3,4)5/h5H Key: WZCZNEGTXVXAAS-UHFFFAOYSA-N
SMILES C(O)(F)(F)F
Properties
Chemical formula	CF3OH
Molar mass	86.013 g·mol−1
Appearance	Colorless liquid
Density	1.5±0.1 g/cm3
Melting point	−110.64 °C (−167.15 °F; 162.51 K)
Boiling point	22.4 °C (72.3 °F; 295.5 K) ±30.0°C
Hazards
Flash point	18.9 °C (66.0 °F; 292.0 K) ±15.6°
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Infobox references

Synthesis

Trifluoromethanol eliminates hydrogen fluoride in an endothermic reaction^[3] and forms carbonyl fluoride.^[4]

CF₃OH ⇌ COF₂ + HF

The equilibrium can be shifted toward trifluoromethanol at lower temperatures. If the synthesized trifluoromethanol is protonated by superacids, for example HSbF₆ (fluoroantimonic acid), the equilibrium can be further shifted to the left towards the desired product. Other primary and secondary perfluoroalcohols exhibit similar instability.

At temperatures in the range of −120 °C, trifluoromethanol can be prepared by treating trifluoromethyl hypochlorite with hydrogen chloride:

CF₃OCl + HCl → CF₃OH + Cl₂

In this reaction, the recombination of a partially positively charged chlorine atom (in trifluoromethyl hypochlorite) with a partially negatively charged chlorine atom (in hydrogen chloride) is used as elemental chlorine. The undesired products, by-products chlorine, hydrogen chloride, and chlorotrifluoromethane, can be removed by evaporation at −110 °C. Trifluoromethanol has a melting point of −82 °C and a calculated boiling point of about −20 °C. The boiling point is thus about 85 K lower than that of methanol. This fact can be explained by the absence of intramolecular H—F bonds, which are also not visible in the infrared gas phase spectrum.

Trifluoromethoxide

Trifluoromethoxide (CF₃O⁻) is the conjugate base of trifluoromethanol. Installing the trifluoromethoxy group, trifluoromethoxylation, is a well developed theme in agricultural and medicinal chemistry.^[5]

Solutions or trifluoromethoxide can be prepared by treating carbonyl fluoride with sources of fluoride ion, e.g. NaF):

COF₂ + F⁻ → CF₃O⁻

Some trifluoromethylethers can be cleaved to release trifluoromethoxide.^[6]

CF₃OAr + Nu → [Nu−Ar]⁺[CF₃O]⁻ (Nu = nucleophile, Ar = aryl group)

Trifluoromethyl benzoate is a related source of the trifluoromethoxide ion.^[7]

In aqueous media, the CF₃O⁻ decomposes at the room temperature.

Occurrence in upper layers of atmosphere

While trifluoromethanol is unstable under normal conditions, it is generated in the stratosphere from CF−3 and CF₃O⁻ radicals by reaction with OF⁺ and F⁻ radicals. In this case, decomposition of trifluoromethanol is negligible under the conditions prevailing in the atmosphere due to the high activation energy of the reaction. The expected lifetime of trifluoromethanol is several million years at altitudes below 40 km.^[8][9]

See also

• Trifluoroethanol