Oxygen difluoride

Oxygen difluoride is a chemical compound with the formula OF₂. 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

Structure and dimensions of the oxygen difluoride molecule
Space-filling model of the oxygen difluoride molecule
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
ECHA InfoCard	100.029.087
EC Number	231-996-7
PubChem CID	24547
RTECS number	RS2100000
UNII	7BCS2CW398 Y
CompTox Dashboard (EPA)	DTXSID20894009
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	OF2
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[a])
Structure
Point group	C2V
Thermochemistry
Heat capacity (C)	43.3 J/mol K
Std molar entropy (S⦵298)	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 labelling:[2]
Pictograms
Signal word	Danger
Hazard statements	H270, H314, H330
NFPA 704 (fire diamond)	4 0 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)[4]
REL (Recommended)	C 0.05 ppm (0.1 mg/m3)[4]
IDLH (Immediate danger)	0.5 ppm[4]
Related compounds
Related compounds	HFO O2F2 NHF2 NF3 SCl2 H2O Cl2O Br2O I2O
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). Y verify (what is YN ?) Infobox references

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 F₂ + 2 NaOH → OF₂ + 2 NaF + H₂O

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, OF₂ decomposes to oxygen and fluorine by a radical mechanism.

2 OF₂ → O₂ + 2 F₂

OF₂ reacts with many metals to yield oxides and fluorides. Nonmetals also react: phosphorus reacts with OF₂ to form PF₅ and POF₃; sulfur gives SO₂ and SF₄; and unusually for a noble gas, xenon reacts (at elevated temperatures) yielding XeF₄ and xenon oxyfluorides.

Oxygen difluoride reacts with water to form hydrofluoric acid:

OF₂ + H₂O → 2 HF + O₂

It can oxidize sulfur dioxide to sulfur trioxide and elemental fluorine:

OF₂ + SO₂ → SO₃ + F₂

However, in the presence of UV radiation, the products are sulfuryl fluoride (SO₂F₂) and pyrosulfuryl fluoride (S₂O₅F₂):

OF₂ + 2 SO₂ → S₂O₅F₂

Safety

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 OF₂ 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 OF₂ would be a solid at 30 K, the fictional alien lifeforms were described as endothermic, maintaining elevated body temperatures and liquid OF₂ blood by radiothermal heating.

Notes

1. This is its critical temperature, which is below ordinary room temperature.