Chlorine monofluoride

Chlorine monofluoride is a volatile interhalogen compound with the chemical formula ClF. It is a colourless gas at room temperature and is stable even at high temperatures. When cooled to −100 °C, ClF condenses as a pale yellow liquid. Many of its properties are intermediate between its parent halogens, Cl₂ and F₂.^[1]

Chlorine monofluoride

Names
IUPAC name Chlorine monofluoride
Other names Chlorine fluoride
Identifiers
CAS Number	7790-89-8 Y
3D model (JSmol)	Interactive image
ChemSpider	109879 N
ECHA InfoCard	100.029.300
PubChem CID	123266
UNII	UE4699O6C6 Y
CompTox Dashboard (EPA)	DTXSID50894057
InChI InChI=1S/FCl/c1-2 N Key: OMRRUNXAWXNVFW-UHFFFAOYSA-N N InChI=1/FCl/c1-2 Key: OMRRUNXAWXNVFW-UHFFFAOYAD
SMILES FCl
Properties
Chemical formula	ClF
Molar mass	54.45 g·mol−1
Appearance	Colorless gas (slightly yellow when liquid)
Density	1.62 g/mL (liquid, −100 °C)
Melting point	−155.6 °C (−248.1 °F; 117.5 K)
Boiling point	−100.1 °C (−148.2 °F; 173.1 K)
Solubility in water	reacts violently
Structure
Dipole moment	0.881 D (2.94 × 10−30 C m)
Thermochemistry
Heat capacity (C)	33.01 J/(mol·K)
Std molar entropy (S⦵298)	217.91 J/(mol·K)
Std enthalpy of formation (ΔfH⦵298)	−56.5 kJ/mol
Related compounds
Related compounds	Chlorine trifluoride Chlorine pentafluoride Bromine monofluoride Iodine monofluoride Bromine monochloride Iodine monochloride Iodine monobromide Astatine monofluoride Astatine monochloride Astatine monobromide Astatine monoiodide
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). N verify (what is YN ?) Infobox references

Geometry

The molecular structure in the gas phase was determined by microwave spectroscopy; the bond length is r_e = 1.628341(4) Å.^[2]

The bond length in the crystalline ClF is 1.628(1) Å; the lengthening relative to the free molecule is due to an interaction of the type F-Br···ClMe with a distance of 2.640(1) Å. In its molecular packing it shows very short intermolecular Cl···Cl contacts of 3.070(1) Å between neighboring molecules.^[3]

Reactivity

Chlorine monofluoride is a versatile fluorinating agent, converting metals and non-metals to their fluorides and releasing Cl₂ in the process. For example, it converts tungsten to tungsten hexafluoride and selenium to selenium tetrafluoride:

W + 6 ClF → WF₆ + 3 Cl₂

Se + 4 ClF → SeF₄ + 2 Cl₂

FCl can also chlorofluorinate compounds, either by addition across a multiple bond or via oxidation. For example, it adds fluorine and chlorine to the carbon of carbon monoxide, yielding carbonyl chloride fluoride COClF, an intermediate between phosgene and carbonyl fluoride.

CO + ClF →

Safety

Chlorine monofluoride is extremely reactive. It instantly destroys glass and ignites organic material on contact, reacts violently with water, is highly corrosive to mucous membranes and the skin, eyes, and respiratory tract, and may cause permanent blindness.^[4]

See also

• Chlorine fluorides
• Oxygen monofluoride