Fluoroform
Fluoroform, also known as trifluoromethane, is a chemical compound with the formula CHF3[1]. It is a hydrofluorocarbon and a member of the haloforms, a class of compounds with the formula CHX3 (X = halogen) with C3v symmetry. Fluoroform is used in diverse applications in organic synthesis and is not an ozone depleter but is a greenhouse gas.
Synthesis
Fluoroform is produced industrially as both a by-product of and precursor to the manufacture of Teflon, with an annual production of about 20 million kg. It can be synthesized by the reaction of chloroform with HF:
CHCl3 + 3 HF → CHF3 + 3 HCl
Additionally, it is generated biologically in small amounts, apparently by decarboxylation of trifluoroacetic acid.
Historical
Fluoroform was first obtained by Maurice Meslans in 1894 through the violent reaction of iodoform with dry silver fluoride. The reaction was later improved by Otto Ruff by substituting silver fluoride with a mixture of mercury fluoride and calcium fluoride.
Industrial Applications
Fluoroform is used in the semiconductor industry for plasma etching of silicon oxide and silicon nitride. It is also known as R-23 or HFC-23 and was a useful refrigerant, sometimes used as a replacement for chlorotrifluoromethane (CFC-13). When used as a fire suppressant, it carries the DuPont trade name FE-13, recommended for its low toxicity, low reactivity, and high density.
Organic Chemistry
Fluoroform is weakly acidic with a pKa of 25–28 and is quite inert. Attempted deprotonation results in defluorination to generate F− and difluorocarbene (CF2). Some organocopper and organocadmium compounds have been developed as trifluoromethylation reagents.
Physical Properties
Fluoroform has a molecular weight of 70.0138 and is also known by various other names, including methane, trifluoro-; Arcton 1; Fluoryl; Freon F-23; Freon 23; Genetron 23; Methyl trifluoride; R 23; Trifluoromethane; CHF3; Arcton; Halocarbon 23; UN 1984; Carbon trifluoride; Genetron HFC23; Propellant 23; Refrigerant 23[2]. Its density varies depending on the temperature, with values of 1.52 g/cm3 at -100°C (liquid), 1.431 g/cm3 at -82.1°C (liquid), 4.57 kg/m3 at -82.1°C (gas), 2.86 kg/m3 at 0°C (gas), and 2.99 kg/m3 at 15°C (gas)[1]. It has a dipole moment of 1.649 D and a critical pressure of 4.816 MPa (48.16 bar) at a critical temperature of 25.7°C (299 K)[1].
Safety
Fluoroform is classified as a liquefied gas and is considered hazardous by the OSHA Hazard Communication Standard (29 CFR 1910.1200)[4]. It contains gas under pressure and may explode if heated, cause frostbite, and displace oxygen, leading to rapid suffocation[4]. Precautions include using and storing it only outdoors or in well-ventilated areas, protecting it from sunlight, and storing it in an upright position[4].
Citations:
[1] https://en.wikipedia.org/wiki/Fluoroform
[2] https://webbook.nist.gov/cgi/cbook.cgi?ID=C75467&Mask=40
[3] https://www.merriam-webster.com/dictionary/fluoroform
[4] https://www.airgas.com/msds/001078.pdf
[5] https://www.sciencedirect.com/topics/chemistry/fluoroform