Perfluorooctanesulfonyl fluoride

Content sourced from Wikipedia, licensed under CC BY-SA 3.0.

Perfluorooctanesulfonyl fluoride (POSF) is a man-made chemical used mainly to make PFOS and PFOS-based compounds. POSF itself has a sulfonyl fluoride group and is part of a family of highly fluorinated compounds that are very water- and fat-resistant.

What POSF is and how it’s made
- POSF is produced by electrochemical fluorination (ECF) of octanesulfonyl fluoride in hydrogen fluoride, giving about 25% yield and a mix of isomers (about 70% linear). It can also be made by fluorinating octanesulfonyl chloride.
- It is the precursor to PFOS, PFOS-based polymers, and related chemicals.

History, production, and regulation
- 3M began making POSF in 1949 and expanded production to meet demand for PFOS-based products.
- By the late 1990s POSF/PFOS were among the most produced fluorochemicals, with production peaking in the thousands of tonnes per year.
- From 2000–2002, under environmental pressure, 3M phased out PFOS and POSF production. Production then shifted mainly to China.
- By the mid-2000s, Chinese production of PFOS-based compounds rose, while global production grew overall. Estimates for 2009 put total global production around 120,000 tonnes over its history.
- POSF and PFOS are listed under Annex B of the Stockholm Convention on Persistent Organic Pollutants, with exemptions and a program to reduce production. POSF itself is not banned, but its use is restricted and regulated to limit environmental release.

Environmental fate and health notes
- Most POSF-derived substances degrade to PFOS, a persistent pollutant that is frequently detected in the environment and in biomonitoring studies.
- POSF can slowly hydrolyze in water and reacts with bases to form PFOS salts, or with acids to form PFOS salts or hydrates; it can also react with ammonia to form PFOS sulfonamides.
- PFOS and related compounds are known for their hydrophobic and surface-active properties, which contribute to their environmental persistence and potential health concerns.

Related compounds
- POSF is the starting point for PFOS, PFOS-based polymers, PFOSA (perfluorooctanesulfonamide), PFOA (perfluorooctanoic acid), PFBS (perfluorobutanesulfonic acid), and other fluorinated substances used in industry.

Quick facts
- Chemical formula: C8F18O2S
- Molar mass: about 502 g/mol
- Boiling point: about 154°C

In short, POSF is a key but environmentally problematic precursor to PFOS and related chemicals, historically produced in large quantities, with production shifting to China after phased reductions in the early 2000s, and now regulated under international controls to reduce its use and environmental impact.