Chemistry:Oxygen difluoride
| |
| |
| Names | |
|---|---|
| IUPAC name
Oxygen difluoride
| |
Other names
| |
| Identifiers | |
3D model (JSmol)
|
|
| ChEBI | |
| ChemSpider | |
| EC Number |
|
PubChem CID
|
|
| RTECS number |
|
| UNII | |
| |
| |
| Properties | |
| OF 2 | |
| Molar mass | 53.9962 g/mol |
| Appearance | colorless gas, pale yellow liquid when condensed |
| Odor | peculiar, foul |
| Density |
|
| Melting point | −223.8 °C (−370.8 °F; 49.3 K) |
| Boiling point | −144.75 °C (−228.55 °F; 128.40 K) |
| hydrolyzes[1] slowly | |
| Vapor pressure | 48.9 atm (at −58.0 °C or −72.4 °F or 215.2 K[lower-alpha 1]) |
| Structure | |
| C2V | |
| Thermochemistry | |
Heat capacity (C)
|
43.3 J/mol K |
Std molar
entropy (S |
247.46 J/mol K |
Std enthalpy of
formation (ΔfH⦵298) |
24.5 kJ mol−1 |
Gibbs free energy (ΔfG˚)
|
41.8 kJ/mol |
| Hazards | |
| GHS pictograms |   
|
| GHS Signal word | danger |
| Template:HPhrases | |
| Template:PPhrases | |
| NFPA 704 (fire diamond) | |
| Lethal dose or concentration (LD, LC): | |
LC50 (median concentration)
|
|
| NIOSH (US health exposure limits): | |
PEL (Permissible)
|
TWA 0.05 ppm (0.1 mg/m3)[2] |
REL (Recommended)
|
C 0.05 ppm (0.1 mg/m3)[2] |
IDLH (Immediate danger)
|
0.5 ppm[2] |
| Related compounds | |
Related compounds
|
|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). | |
 verify (what is   ?)
| |
| Infobox references | |
Oxygen difluoride is a chemical compound with the formula OF
2. As predicted by VSEPR theory, the molecule adopts a bent molecular geometry.[citation needed] It is a strong oxidizer and has attracted attention in rocketry for this reason.[5] With a boiling point of −144.75 °C, OF2 is the most volatile (isolable) triatomic compound.[6] The compound is one of many known oxygen fluorides.
Preparation
Oxygen difluoride was first reported in 1929; it was obtained by the electrolysis of molten potassium fluoride and hydrofluoric acid containing small quantities of water.[7][8] The modern preparation entails the reaction of fluorine with a dilute aqueous solution of sodium hydroxide, with sodium fluoride as a side-product:
- 2 F
2 + 2 NaOH → OF
2 + 2 NaF + H
2O
Structure and bonding
It is a covalently bonded molecule with a bent molecular geometry and a F-O-F bond angle of 103 degrees. Its powerful oxidizing properties are suggested by the oxidation number of +2 for the oxygen atom instead of its normal −2.
Reactions
Above 200 °C, OF
2 decomposes to oxygen and fluorine by a radical mechanism.
- 2 OF
2 → O
2 + 2 F
2
OF
2 reacts with many metals to yield oxides and fluorides. Nonmetals also react: phosphorus reacts with OF
2 to form PF
5 and POF
3; sulfur gives SO
2 and SF
4; and unusually for a noble gas, xenon reacts (at elevated temperatures) yielding XeF
4 and xenon oxyfluorides.
Reactions of oxygen difluoride and hydrogen halides or halide salts produce the free halogen. For example:
4 HCl + OF
2 → 2 HF + H
2O + 2 Cl
2
Oxygen difluoride reacts with water to form hydrofluoric acid:
- OF
2 + H
2O → 2 HF + O
2
It can oxidize sulfur dioxide to sulfur trioxide and elemental fluorine:
- OF
2 + SO
2 → SO
3 + F
2
However, in the presence of UV radiation, the products are sulfuryl fluoride (SO
2F
2) and pyrosulfuryl fluoride (S
2O
5F
2):
- OF
2 + 2 SO
2 → S
2O
5F
2
Safety
Oxygen difluoride is considered an unsafe gas due to its oxidizing properties. It reacts explosively with water, hydrogen sulfide, diborane, and nitrogen oxides.[9] Hydrofluoric acid produced by the hydrolysis of OF
2 with water is highly corrosive and toxic, capable of causing necrosis, leaching calcium from the bones and causing cardiovascular damage, among a host of other highly toxic effects. Other acute poisoning effects include: pulmonary edema, bleeding lungs, headaches, etc.[10] Chronic exposure to oxygen difluoride, like that of other chemicals that release fluoride ions, can lead to fluorosis and other symptoms of chronic fluoride poisoning. Oxygen difluoride may be associated with kidney damage.[10] The maximum workplace exposure limit is 0.05 ppm.[11][10]
Popular culture
In Robert L. Forward's science fiction novel Camelot 30K, oxygen difluoride was used as a biochemical solvent by fictional life forms living in the solar system's Kuiper belt. While OF
2 would be a solid at 30 K, the fictional alien lifeforms were described as endothermic, maintaining elevated body temperatures and liquid OF
2 blood by radiothermal heating.
Notes
- ↑ This is its critical temperature, which is below ordinary room temperature.
References
- ↑ "difluorine monoxide; oxygen difluoride, physical properties, suppliers, CAS, MSDS, structure, Molecular Formula, Molecular Weight, Solubility, boiling point, melting point". http://www.chemyq.com/En/xz/xz1/2818mqnrv.htm.
- ↑ 2.0 2.1 2.2 NIOSH Pocket Guide to Chemical Hazards. "#0475". National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/npg/npgd0475.html.
- ↑ "Oxygen difluoride". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH). https://www.cdc.gov/niosh/idlh/7783417.html.
- ↑ GHS: GESTIS 570242
- ↑ Forbes, Forrest S.; Van Splinter, Peter A. (2003). "Liquid Rocket Propellants". Encyclopedia of Physical Science and Technology. pp. 741–777. doi:10.1016/B0-12-227410-5/00385-9. ISBN 978-0-12-227410-7.
- ↑ Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. p. 819. ISBN 978-0-08-037941-8.
- ↑ Lebeau, P.; Damiens, A. (1929). "Sur un nouveau mode de préparation du fluorure d'oxygène" (in fr). Comptes rendus hebdomadaires des séances de l'Académie des Sciences 188: 1253–1255. http://visualiseur.bnf.fr/CadresFenetre?O=NUMM-3141&I=1253&M=chemindefer. Retrieved February 21, 2013.
- ↑ Lebeau, P.; Damiens, A. (1927). "Sur l'existence d'un composé oxygéné du fluor" (in fr). Comptes rendus hebdomadaires des séances de l'Académie des Sciences 185: 652–654. http://visualiseur.bnf.fr/CadresFenetre?O=NUMM-3138&I=652&M=tdm. Retrieved February 21, 2013.
- ↑ "OXYGEN DIFLUORIDE | CAMEO Chemicals | NOAA". https://cameochemicals.noaa.gov/chemical/4148.
- ↑ 10.0 10.1 10.2 "1449". https://www.kdocs.cn/singleSign4CST?cb=https%3A%2F%2Fwww.kdocs.cn%2Fl%2Fcn9j8vXb7Gq3%3Ff%3D201&ts=1715699652.
- ↑ "CDC - NIOSH Pocket Guide to Chemical Hazards - Oxygen difluoride". https://www.cdc.gov/niosh/npg/npgd0475.html.
External links
- National Pollutant Inventory - Fluoride and compounds fact sheet
- WebBook page for OF
2 - CDC - NIOSH Pocket Guide to Chemical Hazards
 |  |
