Trifluoromethanol

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)	DTXSID00164217
InChI InChI=1S/CHF3O/c2-1(3,4)5/h5H Key: WZCZNEGTXVXAAS-UHFFFAOYSA-N
SMILES C(O)(F)(F)F
Properties
Chemical formula	CHF3O
Molar mass	86.013 g·mol−1
Appearance	Colorless liquid
Density	1.5±0.1 g/cm3
Melting point	-110.64
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

Trifluoromethanol is a synthetic organic compound with the formula CHF
₃O.^[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.

Synthesis

Like all primary and secondary perfluoroalcohols, trifluoromethanol eliminates hydrogen fluoride in an endothermic reaction^[3] and forms carbonyl fluoride.^[4]

CF
₃OH ⇌ COF
₂ + HF (I)

At temperatures in the range of -120 °C, trifluoromethanol can be prepared from trifluoromethyl hypochlorite and hydrogen chloride:

CF
₃OCl + HCl → CF
₃OH + Cl
₂ (II)

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.

A simpler synthesis uses the reaction (I); an equilibrium can be shifted to the thermodynamically preferred trifluoromethanol at lower temperatures. If the synthesized trifluoromethanol is protonated by superacids, for example HSbF
₆ (fluoroantimonic acid), the equilibrium can be further shifted to the left towards the desired product.

Similar to reaction (I), trifluoromethoxides (CF
₃O⁻
) can be prepared from saline-type fluorides (e.g., NaF) and carbonyl fluoride. However, if the CF
₃O⁻
ion is, for example, in an aqueous solution displaced by an acid, trifluoromethanol 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 CF
₃O⁻
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.^[5][6]

See also

• Trifluoroethanol

References