Perfluorooctanesulfonyl fluoride

Perfluorooctanesulfonyl fluoride (POSF) is a synthetic perfluorinated compound with a sulfonyl fluoride functional group. It is used to make perfluorooctanesulfonic acid (PFOS) and PFOS-based compounds. These compounds have a variety of industrial and consumer uses, but POSF-derived substances ultimately degrade to form PFOS.
Because of environmental concerns over PFOS, 3M ceased POSF use in 2002 and global production plummeted. However, Chinese production grew after 3M's phaseout. As of May 2009, POSF and PFOS are listed as persistent organic pollutants (POPs) included in Annex B of the Stockholm Convention.
Production.
In 1949, 3M began producing POSF by electrochemical fluorination (ECF). From 1966 to the 1990s, 3M production increased to meet demand for POSF-based compounds. In 1999, 3M reported POSF was its most highly produced fluorochemical. Before 2000, 3M was the largest global producer of POSF (mainly at their Decatur, AL and Antwerp facilities) and global production peaked at ~4500 tonnes per year.
In 1999, the U.S. Environmental Protection Agency began investigating perfluorinated compounds after receiving data on the global distribution and toxicity of PFOS, the key ingredient in Scotchgard. For these reasons, and USEPA pressure, the primary American producer of PFOS, 3M, announced, in May 2000, the phaseout of the production of PFOS, PFOA, and PFOS-related products. 3M stated that they would have made the same decision regardless of USEPA pressure.
Immediately after the 2000–2002 3M phaseout, production plummeted, but dominant and growing production shifted to China. In 2004 Chinese production of PFOS-based compounds was estimated to be <50 tonnes. In 2005 global production was estimated to be between 73–162 tonnes, and by 2006 Chinese production was estimated at >200 tonnes. Total historical global production was estimated at ~120,000 tonnes in 2009.
"[M]ost, if not all" industrially synthesized perfluorooctanesulfonyl derivatives, such as PFOS, have POSF as their precursor.
Synthesis.
POSF is synthesized by electrochemical fluorination of octanesulfonyl fluoride in anhydrous hydrogen fluoride by the equation:
This reaction results in a 25% yield for POSF, less than that for shorter perfluorosulfonyl fluorides. The POSF obtained is impure as it is a mixture of linear and branched isomers, with ∼70% linear. POSF can also be obtained by ECF of the sulfonyl halide octanesulfonyl chloride.
Reactivity.
POSF and POSF-based polymers degrade to form PFOS which is not known to degrade by any environmental processes. POSF hydrolysis in water, however, occurs slowly.
POSF reacts with bases such as potassium hydroxide to form PFOS salts:
Upon treatment with sulfuric acid the sulfonic acid PFOS tetrahydrate is obtained.
POSF also reacts with ammonia to form perfluorooctanesulfonamide:
Sulfonamides and sulfonamidoethanols synthesized from POSF can in turn react to form a variety of different functional groups for different applications and products.
Uses.
Because of multiple carbon–fluorine bonds, POSF-derivatives have chemical properties that are hydrophobic ("water-afraid"), lipophobic ("fat-afraid"), and surface tension lowering (as fluorosurfactants). The main uses of chemical substances derived from POSF have been:
The Stockholm Convention lists a variety of acceptable purposes and specific exemptions for POSF and PFOS (and it salts) including
International status.
At the Fourth Conference of Parties, decision SC-4/17 put POSF, along with PFOS, in the Stockholm Convention on Persistent Organic Pollutants (Annex B) in May 2009. As such, POSF is not "banned" but has approved uses and exemptions—along with a program (SC-4/19) in Annex B that encourages reduced production.
Environmental concern.
The POSF degradation product, PFOS, is the dominant perfluorinated compound detected in biomonitoring studies, where concentrations that have been detected are considered sufficient to "alter health parameters".