Trifluoromethanol is the organic compound with the formula . It is also referred to as perfluoromethanol or trifluoromethyl alcohol. The compound is the simplest
perfluoroalcohol. 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 and forms
carbonyl fluoride
Carbonyl fluoride is a chemical compound with the formula COF2. It is a carbon oxohalide. This gas, like its analog phosgene, is colourless and highly toxic. The molecule is planar with ''C''2v symmetry, bond lengths of 1.174 Å (C=O) and 1.312 ...
.
: ⇌ + (I)
At temperatures in the range of -120 °C, trifluoromethanol can be prepared from trifluoromethoxy chloride and
hydrogen chloride
The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...
:
: + → + (II)
In this reaction, the recombination of a partially positively charged chlorine atom (in trifluoromethoxy chloride) with a partially negatively charged chlorine atom (in hydrogen chloride) is used as elemental chlorine. The undesired products, by-products chlorine,
hydrogen chloride
The compound hydrogen chloride has the chemical formula and as such is a hydrogen halide. At room temperature, it is a colourless gas, which forms white fumes of hydrochloric acid upon contact with atmospheric water vapor. Hydrogen chloride ga ...
, 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 (
fluoroantimonic acid
Fluoroantimonic acid is a mixture of hydrogen fluoride and antimony pentafluoride, containing various cations and anions (the simplest being and ). This substance is a superacid that can be over a billion times stronger than 100% pure sulfuri ...
), the equilibrium can be further shifted to the left towards the desired product.
Similar to reaction (I), trifluoromethoxides () can be prepared from saline-type fluorides (e.g., ) and
carbonyl fluoride
Carbonyl fluoride is a chemical compound with the formula COF2. It is a carbon oxohalide. This gas, like its analog phosgene, is colourless and highly toxic. The molecule is planar with ''C''2v symmetry, bond lengths of 1.174 Å (C=O) and 1.312 ...
. However, if the 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 and radicals by reaction with and 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.
See also
*
Trifluoroethanol
2,2,2-Trifluoroethanol is the organic compound with the formula CF3CH2OH. Also known as TFE or trifluoroethyl alcohol, this colourless, water-miscible liquid has a smell reminiscent of ethanol. Due to the electronegativity of the trifluoromethyl ...
References
{{Alcohols
Trifluoromethyl compounds
Primary alcohols
Trifluoromethoxy compounds
Organic compounds with 1 carbon atom
Substances discovered in the 1970s