Hexafluoroacetone (HFA) is a
chemical compound
A chemical compound is a chemical substance composed of many identical molecules (or molecular entities) containing atoms from more than one chemical element held together by chemical bonds. A molecule consisting of atoms of only one element ...
with the
formula (CF
3)
2CO. It is structurally similar to
acetone
Acetone (2-propanone or dimethyl ketone), is an organic compound with the formula . It is the simplest and smallest ketone (). It is a colorless, highly volatile and flammable liquid with a characteristic pungent odour.
Acetone is miscib ...
; 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 (1.5
H2O), which is a
hemihydrate of
hexafluoropropane-2,2-diol , a
geminal diol
In chemistry, the descriptor geminal () refers to the relationship between two atoms or functional groups that are attached to the same atom. A geminal diol, for example, is a diol (a molecule that has two alcohol functional groups) attached t ...
.
Synthesis
The industrial route to HFA involves treatment of
hexachloroacetone
Hexachloroacetone is an organic compound with the formula (Cl3C)2CO. It is also called hexachloropropanone or perchloroacetone. Numbers indicating the position of the chlorine-atoms are generally omitted as all the possible positions are substitut ...
with
HF:
:(CCl
3)
2CO + 6 HF → (CF
3)
2CO + 6 HCl
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
3)2CS">CF3)2CSsub>2. This species is then oxidized by iodate to give (CF
3)
2CO.
Uses
Hexafluoroacetone is used in the production of
hexafluoroisopropanol
Hexafluoroisopropanol, commonly abbreviated HFIP, is the organic compound with the formula (CF3)2CHOH. This fluoroalcohol finds use as solvent and synthetic intermediate. It appears as a colorless, volatile liquid that is characterized by a stro ...
:
:(CF
3)
2CO + H
2 → (CF
3)
2CHOH
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
Midaflur ( INN; EXP 338) is an extremely stable 3-imidazoline derivative with central skeletal muscle relaxant and sedative properties in humans and other species of mammals, exhibiting consistently high oral bioavailability and a long duration ...
, bisphenol AF, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, and alitame
Alitame is an aspartic acid-containing dipeptide sweetener. It was developed by Pfizer in the early 1980s and currently marketed in some countries under the brand name Aclame. Most dipeptides are not sweet, but the unexpected discovery of aspart ...
.
Reactivity
Hexafluoroacetone is an electrophile
In chemistry, an electrophile is a chemical species that forms bonds with nucleophiles by accepting an electron pair. Because electrophiles accept electrons, they are Lewis acids. Most electrophiles are positively charged, have an atom that carrie ...
. Nucleophiles attack at the carbonyl
In organic chemistry, a carbonyl group is a functional group composed of a carbon atom double-bonded to an oxygen atom: C=O. It is common to several classes of organic compounds, as part of many larger functional groups. A compound containi ...
carbon. In water, hexafluoroacetone predominantly exists as the hydrate. The equilibrium constant
The equilibrium constant of a chemical reaction is the value of its reaction quotient at chemical equilibrium, a state approached by a dynamic chemical system after sufficient time has elapsed at which its composition has no measurable tendency ...
(Keq) for the formation of this geminal diol
In chemistry, the descriptor geminal () refers to the relationship between two atoms or functional groups that are attached to the same atom. A geminal diol, for example, is a diol (a molecule that has two alcohol functional groups) attached t ...
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
Ammonia is an inorganic compound of nitrogen and hydrogen with the formula . A stable binary hydride, and the simplest pnictogen hydride, ammonia is a colourless gas with a distinct pungent smell. Biologically, it is a common nitrogenous wa ...
adds to hexafluoroacetone to give the hemiaminal (CF3)2C(OH)(NH2) which can be dehydrated with phosphoryl chloride to give the imine
In organic chemistry, an imine ( or ) is a functional group or organic compound containing a carbon–nitrogen double bond (). The nitrogen atom can be attached to a hydrogen or an organic group (R). The carbon atom has two additional single bon ...
(CF3)2CNH.[.]
See also
* Bromoacetone
* Chloroacetone
* Fluoroacetone
* Trifluoroacetone
* Novec 1230
* Hexafluorothioacetone
References
{{Reflist
Trifluoromethyl compounds
Ketones
Perfluorinated compounds
Trifluoromethyl ketones