Chlorine Trifluoride

The interhalogen compound with ClF3 chemical formula is called Chlorine Trifluoride. ClF3 is a poisonous, colorless, corrosive, extremely reactive gas with a sweet and suffocating pungent type of odor. Chloride Trifluoride is available in the condensed form in the market and at pressurized room temperature it turns into a pale-greenish yellow liquid. The compound causes severe irritation to mucous membranes, eyes, and skin, and on exposure to the Chlorine Trifluoride gas, it can cause lung damage. Chlorine Trifluoride is used as a component in rocket fuels as it is a powerful oxidizer, and when most combustible elements come in contact with ClF3, then it ignites quite spontaneously.

Chlorine Trifluoride Structure 

The structure of Chlorine Trifluoride in terms of molecular geometry has two long bonds and one short bond and has almost a T-shaped. In the ClF3 molecule, the central chlorine atom has five regional electron densities (three bonds and two lone pairs). 

The structure of Chlorine Trifluoride predicts that the lone pairs of the electrons being present in the two equatorial positions of a say trigonal bipyramid, which satisfies the VSEPR Theory. 

These are arranged at 175 degrees of F(axial)-Cl-F(axial) bond angle, and the elongated axial bonds of Cl-F bonds are consistent using hypervalent bonding. 

And pure Chlorine Trifluoride is stable to 180 degrees Celsius in a quartz vessel, but above this temperature, it decomposes to its constituent elements by a free radical mechanism.

The Properties Of Chlorine Trifluoride 

Chlorine Trifluoride is a chemical compound that is not present as a free compound in nature. It is precarious and highly combustible. ClF3 has a density of 1.77g/cm3 and a molecular mass of 92.448g/mol. The boiling point of Chlorine Trifluoride is 11.75 degrees Celsius, and the melting point of the compound is -76.34 degrees Celsius. The molecule of Chlorine Trifluoride has one covalently-bonded unit, and there are four heavy atoms present. Chlorine Trifluoride is surprisingly soluble in water. 

Chlorine Trifluoride in the vapor state may decompose to ClF, ClOF, ClO2F, ClO3F, ClO2, Cl2, and HF, among which the most significant ones are Cl2, ClO2, and HF. But all the resultants of the decomposition depend on the availability of water.

Why Is Chlorine Trifluoride So Fatal? 

ClF3 coming in contact with any element it evaporates into toxic gas, and when ClF3 ignites, it burns at over 2400 degrees Celsius. The chemical is even more oxidizing than Oxygen, makes it an excellently effective explosive. Chlorine Trifluoride can set fire to even some inflammable materials like sand, glass, or asbestos, and ClF3 can also ignite the already burnt elements like a pile of ash can be reignited. On decomposition, ClF3 produces hydrofluoric and hydrochloric acid in a steam form. 

Uses Of Chlorine Trifluoride 

Chlorine Trifluoride is mainly used as a component in plasma-less cleaning and etching operations.

ClF3 is also used in nuclear reactor fuel processing. To convert uranium into gaseous hexafluoride uranium, Chlorine Trifluoride is used.

Chlorine Trifluoride is used as a component in rocket fuels. But there are several problems regarding the use of ClF3 as a component in the rocket propellant systems. ClF3 is known to be rapidly hypergolic with all other fuels and doesn't make any measurable ignition delay.  

In the semiconductor industry, ClF3 is used to clean chemical vapor deposition chambers. Another benefit of using Chlorine Trifluoride is that it can be used to remove the chamber walls' semiconductor material without the need to dismantle. ClF3 does not require to be activated by plasma because the heat of the chamber is enough for decomposition and reaction with the semiconductor material. 

Uranium Hexafluoride (UF6) production is also one of the primary uses of ClF3, uranium metal goes under the process of fluorination as part of nuclear fuel processing and reprocessing.

U + 3ClF3 -> UF6 + 3ClF

Solved Examples 

  • The reactions of Chlorine Trifluoride with many metals yield chlorides and fluorides. 

  • ClF3, when reacts with Phosphorus (P2), then it produces Phosphorus Trichloride (PCl3) and Phosphorus Pentafluoride (PF5). 

  • When ClF3 acts with Sulphur (S2), then it yields Sulphur Dichloride (SCl2) and Sulphur Tetrafluoride (SF4).

  • Chlorine Trifluoride reacts violently with water by either oxidizing it to provide Oxygen gas or to provide Oxygen Difluoride (OF2) in controlled amounts. Also, the reduction will cause Hydrogen Fluoride and Hydrogen Chloride. 

ClF3 + 2H2O -> 3HF + HCl + O2

ClF3 + H2O -> HF + HCl +OF2

Hence, it is quite impossible to store Fluorine in solutions because it is the most powerful oxidizing agent of all elements.

Fun Fact 

In a laboratory experiment, the exposure of 400ppm of Chlorine Trifluoride gas for thirty minutes was lethal to the rats.

Chlorine Trifluoride (ClF3) has 28 valence electrons in total, and the bonds are between the center Chlorine atom and the surrounding three Fluorine atoms. The three polarized bonds in ClF3 combine to result in a small molecular dipole along with the bond between Cl and F. 

FAQ (Frequently Asked Questions)

1. What is the history of Chlorine Trifluoride?

Otto Ruff and H. Krug in the 1930s isolated the liquid compound Chlorine Trifluoride (ClF3), which was even more reactive than Fluorine. The compound they formed was highly combustible and explosive. Nazis took an interest in ClF3 during World War II to make powerful bombs and flamethrowers. But the massive quantity of production was reduced once they realized that the compound was volatile and reactive, and it was not wise to keep producing more than the 30 tons already made. Even so, ClF3 was never used in combat thankfully. And since the war, the ClF3 compound has been banned under the Chemical Weapons Convention because of its highly destructive nature. 

How is Chlorine Trifluoride formed, and how must it be stored?

The ClF3 is formed by cation Chloride in the center, which is bound to three Fluoride anions. The Chloride atoms have two lone pairs of electrons that form a trigonal bipyramidal structure of the molecule due to the repulsion caused by the electron over Fluoride atoms.  

For safely storing and sealing Chlorine Trifluoride use containers made of steel, iron, copper, and nickel after they've been treated with Fluorine gas. The thin Fluoride layer formed inside the container created by processing the container with Fluorine doesn't disturb the ClF3. If the coating step is not done right, then an explosion might occur when ClF3 comes into contact with the vessel.