Oxygen difluoride

Oxygen difluoride

Names
IUPAC name Oxygen difluoride
Other names Oxygen fluoride Hypofluorous anhydride
Identifiers
CAS Number	7783-41-7 Y
3D model (JSmol)	Interactive image
ChEBI	CHEBI:30494 Y
ChemSpider	22953 Y
EC Number	231-996-7
PubChem CID	24547
RTECS number	RS2100000
UNII	7BCS2CW398 Y
InChI InChI=1S/F2O/c1-3-2 Y Key: UJMWVICAENGCRF-UHFFFAOYSA-N Y InChI=1/F2O/c1-3-2 Key: UJMWVICAENGCRF-UHFFFAOYAI
SMILES FOF
Properties
Chemical formula	OF 2
Molar mass	53.9962 g/mol
Appearance	colorless gas, pale yellow liquid when condensed
Odor	peculiar, foul
Density	1.90 g/cm3 (−224 °C, liquid) 1.719 g/cm3 (−183 °C, liquid) 1.521 g/cm3 (liquid at −145 °C) 1.88 g/L (gas at room temperature)
Melting point	−223.8 °C (−370.8 °F; 49.3 K)
Boiling point	−144.75 °C (−228.55 °F; 128.40 K)
Solubility in water	hydrolyzes[1] slowly
Vapor pressure	48.9 atm (at −58.0 °C or −72.4 °F or 215.2 K[lower-alpha 1])
Structure
Point group	C2V
Thermochemistry
Heat capacity (C)	43.3 J/mol K
Std molar entropy (So298)	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
GHS hazard statements	Template:HPhrases
GHS precautionary statements	Template:PPhrases
NFPA 704 (fire diamond)	0 4 3 OX
Lethal dose or concentration (LD, LC):
LC50 (median concentration)	2.6 ppm (rat, 1 hour) 1.5 ppm (mouse, 1 hour) 26 ppm (dog, 1 hour) 16 ppm (monkey, 1 hour) [3]
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	HFO O 2F 2 NHF 2 NF 3 SCl 2 H 2O Cl 2O Br 2O I 2O
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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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.

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

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.

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.

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

Oxygen difluoride is considered an unsafe gas due to its oxidizing properties. It reacts explosively with water.^[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]

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.

• National Pollutant Inventory - Fluoride and compounds fact sheet
• WebBook page for OF
  2
• CDC - NIOSH Pocket Guide to Chemical Hazards

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