thumb|Oxygen difluoride
Oxygen fluorides are compounds of elements oxygen and fluorine with the general formula , where n = 1 to 6. Many different oxygen fluorides are known:
- Oxygen monofluoride (OF)
- Oxygen difluoride ()
- Dioxygen difluoride ()
- Trioxygen difluoride or ozone difluoride ()
- Tetraoxygen difluoride ()
- Dioxygen monofluoride or fluoroperoxyl ()
thumb|Tetraoxygen difluoride
Oxygen fluorides are strong oxidizing agents with high energy and can release their energy either instantaneously or at a controlled rate. Thus, these compounds attracted much attention as potential oxidizers in jet propulsion systems.
Synthesis, properties and reactions
Oxygen difluoride ()
thumb|Oxygen difluoride
A common preparative method involves fluorination of sodium hydroxide:
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is a colorless gas at room temperature and a yellow liquid below 128 K. Oxygen difluoride has an irritating odor and is poisonous. It reacts quantitatively with aqueous haloacids to give free halogens:
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It can also displace halogens from their salts.
Dioxygen difluoride ()
thumb|Dioxygen difluoride
precipitates as a brown solid upon the UV irradiation of a mixture of liquid and at −196 °C. It also only appears to be stable below −160 °C. The general method of preparation of many oxygen fluorides is a gas-phase electric discharge in cold containers including .
: (electric discharge, 183 °C)
It is typically an orange-yellow solid which rapidly decomposes to and close to its normal boiling point of about 216 K.
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General preparation of polyoxygen difluorides
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!Reaction equation
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Net reaction:
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Hypergolic propellant
Despite the low solubility of in liquid oxygen, it has been shown to be hypergolic with most rocket propellant fuels. The mechanism involves the boiling off oxygen from the solution containing , making it more reactive to have a spontaneous reaction with the rocket fuel. The degree of reactivity is also dependent on the type of fuel used.