Nonafluoro-tert-butyl alcohol
Nonafluoro-tert-butyl alcohol is a fluoroalcohol. It is the perfluorinated analog of tert-butyl alcohol. Notably, as a consequence of its electron withdrawing fluorine substituents, it is very acidic for an alcohol, with a pKa value of 5.4, similar to that of a carboxylic acid. As another consequence of being a perfluorinated compound, it is also one of the lowest boiling alcohols, with a boiling point lower than that of methanol. It is prepared by addition of trichloromethyllithium to hexafluoroacetone, followed by halogen exchange with antimony pentafluoride. The aluminate derived from its alkoxide anion, tetrakisaluminate, – is used as a weakly coordinating anion.
Nonafluoro-tert-butyl alcohol hydrogen-bonds to Lewis bases in non-aqueous solvents such as alkanes and CCL4. 3COH is classified as a hard Lewis acid and its acceptor properties are discussed in the ECW model. When 3COH bonds to a Lewis base, the intramolecular hydrogen bonding in 3COH between the hydroxyl proton and the - CF3 fluorine must to broken. The energy needed to cleave the internal hydrogen bonding of 3COH has been estimated by the ECW model to be 3.6 kJ mol−1.
