Hexafluoroacetone
{{Chembox
| Watchedfields = changed
| verifiedrevid = 445341920
| Name = Hexafluoroacetone
| ImageFile = Hexafluoraceton.svg
| ImageName = Hexafluoropropanone skeletal structure
| ImageFile1 = Hexafluoroacetone 3D.png
| ImageName1 = Hexafluoropropanone 3D structure
| PIN = 1,1,1,3,3,3-Hexafluoropropan-2-one
| OtherNames = perfluoroacetone
acetone hexafluoride
perfluoro-2-propanone
|Section1={{Chembox Identifiers
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 39429
| SMILES = FC(F)(F)C(=O)C(F)(F)F
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 13846015
| InChI = 1/C3F6O/c4-2(5,6)1(10)3(7,8)9
| InChIKey = VBZWSGALLODQNC-UHFFFAOYAI
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C3F6O/c4-2(5,6)1(10)3(7,8)9
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = VBZWSGALLODQNC-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 684-16-2
| PubChem = 12695
| EINECS = 211-676-3
| RTECS = UC2450000
| UNNumber = 2420
| UNII = AKU9463N1Y
}}
|Section2={{Chembox Properties
| Formula = C3F6O
| MolarMass = 166.02 g/mol
| Appearance = Colorless gas
| Density = 1.32 g/ml, liquid
| Solubility = Reacts with water
| MeltingPt = −129 °C (144 K)
| BoilingPt = −28 °C (245 K)
| VaporPressure = 5.8 atm (20 °C)
}}
|Section7={{Chembox Hazards
| ExternalSDS =
| MainHazards = Toxic (T),
Corrosive (C)
| NFPA-H = 3
| NFPA-F =0
| NFPA-R = 2
| NFPA-S = W
| FlashPt_notes = Nonflammable
| GHSPictograms = {{GHS05}}{{GHS06}}{{GHS07}}{{GHS08}}
| GHSSignalWord = Danger
| HPhrases = {{H-phrases|301|310|311|314|315|330|360|370|372}}
| PPhrases = {{P-phrases|201|202|260|262|264|270|271|280|281|284|301+310|301+330+331|302+350|302+352|303+361+353|304+340|305+351+338|307+311|308+313|310|312|314|320|321|322|330|332+313|361|362|363|403+233|405|410+403|501}}
| PEL = none{{PGCH|0319}}
| REL = TWA 0.1 ppm (0.7 mg/m3) [skin]
}}
|Section8={{Chembox Related
| OtherFunction_label = ketones;
organofluorides
| OtherFunction = Acetone;
Hexafluoro-2-propanol
}}
}}
Hexafluoroacetone (HFA) is a chemical compound with the formula (CF3)2CO. It is structurally similar to acetone; however, its reactivity is markedly different. It is a colourless, hygroscopic, nonflammable, highly reactive gas characterized by a musty odour.[https://www.cdc.gov/niosh/npg/npgd0319.html CDC - NIOSH Pocket Guide to Chemical Hazards] According to electron diffraction, HFA and acetone adopt very similar structures, the C-O distance being only longer in the fluorinated compound (124.6 vs 121.0 pm), possibly due to steric effects.{{cite journal |doi=10.1021/j100702a030 |title=Electron diffraction investigation of hexafluoroacetone, hexafluoropropylimine, and hexafluoroisobutene |date=1970 |last1=Hilderbrandt |first1=R. L. |last2=Andreassen |first2=A. L. |last3=Bauer |first3=Simon Harvey |journal=The Journal of Physical Chemistry |volume=74 |issue=7 |pages=1586–1592 }}
The term "hexafluoroacetone" can refer to the sesquihydrate (1.5 H2O), which is a hemihydrate of hexafluoropropane-2,2-diol {{chem|(|F|3|C|)|2|C|(|OH|)|2}}, a geminal diol. Hydrated HFA behaves differently from the anhydrous material.
Synthesis
The industrial route to HFA involves treatment of hexachloroacetone with HF (a Finkelstein reaction):{{cite encyclopedia|author=Günter Siegemund|author2=Werner Schwertfeger|author3=Andrew Feiring|author4=Bruce Smart|author5=Fred Behr|author6=Herward Vogel|author7=Blaine McKusick|title=Fluorine Compounds, Organic|encyclopedia=Ullmann's Encyclopedia of Industrial Chemistry|publisher=Wiley-VCH|place=Weinheim|year=2002|doi=10.1002/14356007.a11_349}}
:(CCl3)2CO + 6 HF → (CF3)2CO + 6 HCl
=Laboratory methods=
Hydrated HFA can be converted to HFA by treatment with hot sulfuric acid.{{cite journal |doi=10.1021/cr0509962 |title=Hexafluoroacetone as Protecting and Activating Reagent: New Routes to Amino, Hydroxy, and Mercapto Acids and Their Application for Peptide and Glyco- and Depsipeptide Modification |date=2006 |last1=Spengler |first1=Jan |last2=Böttcher |first2=Christoph |last3=Albericio |first3=Fernando |last4=Burger |first4=Klaus |journal=Chemical Reviews |volume=106 |issue=11 |pages=4728–4746 |pmid=17091933 }}
It has also be prepared from hexafluoropropylene oxide, which will rearrange to give HFA when heated in the presence of a Lewis acid such as AlCl3.{{cite journal |last1=Millauer |first1=Hans |last2=Schwertfeger |first2=Werner |last3=Siegemund |first3=Günter |title=Hexafluoropropene Oxide — A Key Compound in Organofluorine Chemistry |journal=Angewandte Chemie International Edition in English |date=March 1985 |volume=24 |issue=3 |pages=161–179 |doi=10.1002/anie.198501611}} The Lewis acid catalysed oxidation of hexafluoropropylene will also produce HFA, via a similar mechanism.
Although it is commercially available, HFA can be prepared on the laboratory-scale from hexafluoropropylene.{{cite journal |last1=Anello |first1=Louis G. |last2=Van der Puy |first2=Michael |title=A convenient synthesis of hexafluoroacetone |journal=The Journal of Organic Chemistry |date=January 1982 |volume=47 |issue=2 |pages=377–378 |doi=10.1021/jo00341a046}} In the first step KF catalyzes the reaction of the alkene with elemental sulfur to give the 1,3-dithietane dimer of hexafluorothioacetone. This species is then oxidized by potassium iodate to give HFA.{{OrgSynth | author = Van Der Puy, M. | author2 = Anello, L. G. | title = Hexafluoroacetone | volume = 53 | page = 154 | year = 1985 | doi = 10.15227/orgsyn.063.015}}
Uses
Hexafluoroacetone is used in the production of hexafluoroisopropanol:
:(CF3)2CO + H2 → (CF3)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, bisphenol AF, 4,4′-(hexafluoroisopropylidene)diphthalic anhydride, and alitame.
Reactivity
File:Hexafluoroacetone imine.svg
File:CF3-stabilizedHemiaminal.svg
With water, hexafluoroacetone converts to the hydrate. The equilibrium constant (Keq) for the formation of this geminal diol is 106 M−1. The analogous equilibrium for acetone is an unfavorable 10−3 M−1.{{cite journal |doi=10.1021/jo0302556 |title=Perspective on Fluorocarbon Chemistry |year=2004 |last1=Lemal |first1=David M. |journal=The Journal of Organic Chemistry |volume=69 |pages=1–11 |pmid=14703372 |issue=1}} Hexafluoroacetone-hydrates are acidic. In an analogous reaction, ammonia adds to hexafluoroacetone to give the hemiaminal (CF3)2C(OH)(NH2) which can be dehydrated with phosphoryl chloride to give the imine (CF3)2CNH.{{cite journal| author = W. J. Middleton| author2 = H. D. Carlson | title = Hexafluoroacetone imine | journal= Org. Syntheses | volume = 50| year = 1970| pages=81–3|doi=10.15227/orgsyn.050.0081}}.
Nucleophiles attack occurs at the carbonyl carbon of Hexafluoroacetone, as illustrated above. Thus, HFA readily forms lactones when treated with hydroxy- and amine-substituted carboxylic acids. In such reactions, HFA serves both as electrophile and dehydrating agent:
:{{chem2|RCH(OH)CO2H + O\dC(CF3)2 -> RCH(O)CO2C(CF3)2 + (HO)2C(CF3)2}}