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.
FAQs on Chlorine Trifluoride
1. What is Chlorine Trifluoride and what is its chemical formula?
Chlorine Trifluoride is a highly reactive interhalogen compound, meaning it is formed from two different halogens (chlorine and fluorine). It is a colourless, poisonous, and corrosive gas that condenses to a pale-greenish yellow liquid. Its chemical formula is ClF₃.
2. How is Chlorine Trifluoride (ClF₃) prepared?
Chlorine Trifluoride is typically prepared by the direct reaction of chlorine gas with an excess of fluorine gas. The reaction is carried out at a temperature of 200-300°C in a nickel or copper vessel. The chemical equation for the synthesis is:
Cl₂(g) + 3F₂(g) → 2ClF₃(g)
3. What is the molecular structure and shape of Chlorine Trifluoride (ClF₃)?
The Chlorine Trifluoride molecule has a T-shaped geometry. According to VSEPR (Valence Shell Electron Pair Repulsion) theory, the central chlorine atom has seven valence electrons. It forms three single bonds with three fluorine atoms and has two remaining lone pairs of electrons. These five electron pairs create a trigonal bipyramidal electron geometry. To minimise repulsion, the two lone pairs occupy the equatorial positions, forcing the three Cl-F bonds into a T-shape.
4. What are the primary uses of Chlorine Trifluoride?
Despite its high reactivity and hazardous nature, Chlorine Trifluoride has specific industrial applications. Its main uses include:
- As a powerful fluorinating agent in organic and inorganic chemistry.
- In the nuclear industry to produce Uranium Hexafluoride (UF₆) for uranium enrichment.
- As an igniter and propellant in some rocket propulsion systems.
- For cleaning chemical vapour deposition (CVD) chambers in the semiconductor industry.
5. Why is the ClF₃ molecule T-shaped instead of trigonal planar?
A trigonal planar shape occurs when a central atom is bonded to three other atoms with no lone pairs (e.g., BF₃). However, in ClF₃, the central chlorine atom has three bonding pairs and two lone pairs. According to VSEPR theory, lone pairs exert a greater repulsive force than bonding pairs. The most stable arrangement that minimises this repulsion is a trigonal bipyramidal electron geometry where the two lone pairs occupy the equatorial positions, which are 120° apart. This forces the three fluorine atoms into the remaining axial and equatorial positions, resulting in the observed T-shaped molecular geometry.
6. What happens when Chlorine Trifluoride reacts with water?
The reaction of Chlorine Trifluoride with water is extremely violent and explosive. It hydrolyses rapidly to produce a mixture of dangerous acids, primarily hydrofluoric acid (HF) and hydrochloric acid (HCl), along with oxygen gas. The reaction is highly exothermic and can instantly ignite any combustible materials nearby. The equation is:
ClF₃ + 2H₂O → 3HF + HCl + O₂
7. Why is ClF₃ considered such a powerful fluorinating agent?
Chlorine Trifluoride is an exceptionally powerful fluorinating agent because the Cl-F bonds are relatively weak and the molecule is highly unstable. It readily donates its fluorine atoms to other elements and compounds in highly exothermic reactions. Its ability to oxidise elements to their highest oxidation states, even those typically considered unreactive (like oxides), makes it far more potent than fluorine gas itself under many conditions.
8. Can Chlorine Trifluoride really burn substances that are already burnt, like ash or sand?
Yes, Chlorine Trifluoride is so reactive that it can 'burn' or oxidise materials that are normally considered non-combustible, such as sand (silicon dioxide), asbestos, and concrete. It reacts with silicon dioxide (SiO₂) to produce silicon tetrafluoride and other products in a vigorous reaction. This is not a typical combustion reaction involving oxygen; instead, it's an extremely aggressive oxidation and fluorination process where ClF₃ acts as the oxidiser, stripping electrons and bonding fluorine atoms to the substrate.
9. What are the key safety precautions for handling Chlorine Trifluoride?
Due to its extreme reactivity and toxicity, handling ClF₃ requires stringent safety measures. Key precautions include:
- Using containers made of materials that form a passive fluoride layer, such as nickel, steel, or copper, which prevents further reaction.
- Ensuring all equipment is scrupulously clean and dry, as ClF₃ reacts explosively with water and organic materials.
- Working in a well-ventilated area, typically a fume hood, with appropriate personal protective equipment (PPE), including specialised face shields and gloves.
- Having appropriate fire-suppression systems that do not use water or carbon dioxide, as ClF₃ reacts with both.
10. How does the reactivity of ClF₃ compare with other interhalogen compounds?
Among interhalogen compounds, reactivity generally increases with the difference in electronegativity between the two halogens and decreases as the size of the central atom increases. Chlorine Trifluoride (ClF₃) is considered one of the most reactive interhalogens. It is significantly more reactive than compounds like chlorine monofluoride (ClF) and bromine trifluoride (BrF₃). While BrF₃ is also a powerful fluorinating agent, ClF₃ is generally more vigorous and can fluorinate a wider range of materials under less extreme conditions.
