Hexafluoro-2-propanol

1,1,1,3,3,3-Hexafluoro-2-propanol or Hexafluoroisopropanol (HFIP) is a fluorinated alcohol frequently used as solvent for polymer systems. It appears as a colorless, volatile liquid that is characterized by a strong, pungent odor. As a solvent hexafluoro-2-propanol exhibits strong hydrogen bonding properties enabling it to dissolve a number of molecules with suitable receptive sites such as oxygen atoms, double bonds or amine groups. Hexafluoro-2-propanol is also a polar compound, transparent to UV light with high density, low viscosity and low refractive index.

Production
The first step in the synthesis of hexafluoro-2-propanol is oxidation of hexafluoropropylene to yeld an impure mixture consisting of hexafluoro-2-propanone and residual hexafluoropropylene. This can be done by direct oxidation of hexafluoropropylene using aluminum oxide. The mixture of products thus obtained has to be subsequently reduced in order to hydrogenate hexafluoro-2-propanone to hexafluoro-2-propanol: this is usually achieved by using strong hydrogenating agents such as sodium borohydride in a methanol solution or lithium aluminum hydride or sodium hydride in presence of a reaction promoting solvent such as diethyl ether, methanol, isopropyl alcohol, or tetrahydrofuran. Alternatively catalysts such as Raney nickel or platinum on barium sulfate or palladium on barium sulfate can be employed successfully for direct hydrogenation of hexafluoro-2-propanone. After reduction hexafluoro-2-propanol can be readily separated from residual amounts of hexafluoro-2-propanone and hexafluoropropylene since it has a much higher boiling point than hexafluoro-2-propanone and hexafluoropropilene will outgas easily at about room temperature.

As an alternative hexafluoro-2-propanone mixed with hydrogen fluoride can also be obtained starting from hexachloroacetone.

A different synthetic route to obtain hexafluoro-2-propanol is disclosed in the "US Patent 4,647,706": chemical compounds of the generic formula (CF3)2C-OH-OR (where R represents an hydrogen atom or an alkyl group having from one to eight carbon atoms) are subjected to catalytic hydrogenation in the presence of palladium deposited on activated carbon and of a tertiary aliphatic amine co-catalyst such as triethylamine.

Uses
Hexafluoro-2-propanol is used as a solvent in organic chemistry due to its properties which make it especially useful to solubilize a wide range of polymers, including those that are not soluble in the most common organic solvents: such polymers include polyamides, polyacrylonitriles, polyacetals, polyesters (e.g. polyglycolide) and polyketones. It has also found use in biochemistry to solubilize peptides. Industrially hexafluoro-2-propanol is used as an intermediate for pharmaceuticals (anesthetics) and agrochemicals or as a solvent and cleaner in electronics.

Safety
Hexafluoro-2-propanol is a corrosive chemical and is therefore extremely destructive to tissues of the mucous membranes, upper respiratory tract, skin and eyes, resulting in immediate burns or ulceration. Overexposure by inhalation may result in spasm, inflammation, chemical pneumonitis and larynx, bronchi or pulmonary edema. In case of contact with eyes corneal and conjunctival ulceration or blindness may result. Hexafluoro-2-propanol is not considered carcinogenic, but the effects of a chronic exposure are unknown.