Hexafluoroacetone


Hexafluoroacetone is a chemical compound with the formula 2CO. It is structurally similar to acetone; however, its reactivity is markedly different. It a colourless, hygroscopic, nonflammable, highly reactive gas characterized by a musty odour. The most common form of this substance is hexafluoroacetone sesquihydrate, which is a hemihydrate of hexafluoropropane-2,2-diol, a geminal diol.

Synthesis

The industrial route to HFA involves treatment of hexachloroacetone with HF:
Hexafluoropropylene oxide rearranges to give HFA.
In the laboratory, HFA can be prepared in a two step process from perfluoropropene. In the first step KF catalyzes the reaction of the alkene with elemental sulfur to give the 1,3-dithietane 2. This species is then oxidized by iodate to give 2CO.

Uses

Hexafluoroacetone is used in the production of hexafluoroisopropanol:
It is also used as a precursor to hexafluoroisobutylene, a monomer used in polymer chemistry, and as a building block in the synthesis of midaflur, bisphenol AF, 4,4′-diphthalic anhydride, and alitame.

Reactivity

Hexafluoroacetone is an electrophile. Nucleophiles attack at the carbonyl carbon. In water, hexafluoroacetone predominantly exists as the hydrate. The equilibrium constant for the formation of this geminal diol is 106 M−1. The analogous equilibrium for acetone is an unfavorable 10−3 M−1. Hexafluoroacetone-hydrates are acidic. In an analogous reaction, ammonia adds to hexafluoroacetone to give the hemiaminal 2C which can be dehydrated with phosphoryl chloride to give the imine 2CNH.