Synthesis and structure of environmentally relevant perfluorinated sulfonamides

• Published in: Journal of fluorine chemistry 2007-06, Vol.128 (6), p.595-607
• Main Authors: Lehmler, Hans-Joachim, Rama Rao, V.V.V.N.S., Nauduri, Dhananjaya, Vargo, John D., Parkin, Sean
• Format: Article
• Language: English
• Subjects: Alkylation; Environmental contaminants; Mitsunobu reaction; Perfluorobutanesulfonamides; Perfluorooctanesulfonamides; X-ray structure
• ISSN: 0022-1139; 1873-3328
• DOI: 10.1016/j.jfluchem.2007.01.013

Alkylated perfluorooctanesulfonamides are compounds of environmental concern. To make these compounds available for environmental and toxicological studies, a series of N-alkylated perfluorooctanesulfonamides and structurally related compounds were synthesized by reaction of the corresponding perfluoroalkanesulfonyl fluoride with a suitable primary or secondary amine. Perfluoroalkanesulfonamidoethanols were obtained from the N-alkyl perfluoroalkanesulfonamides either by direct alkylation with bromoethanol or alkylation with acetic acid 2-bromo-ethyl ester followed by hydrolysis of the acetate. N-Alkyl perfluorooctanesulfonamidoacetates were synthesized in an analogous way by alkylation of N-alkyl perfluoroalkanesulfonamides with a bromo acetic acid ester, followed by basic ester hydrolysis. Alternatively, N-alkyl perfluoroalkanesulfonamides can be alkylated with an appropriate alcohol using the Mitsunobu reaction. Perfluorooctanesulfonamide was synthesized from the perfluorooctanesulfonyl fluoride via the azide by reduction with Zn/HCl. All perfluorooctanesulfonamides contained linear as well as branched C 8F 17 isomers, typically in a 10:1 to 30:1 ratio. The crystal structures of N-ethyl and N, N-diethyl perfluorooctanesulfonamide show that the S–N bond has considerable double bond character. This double bond character results in a significant rotational barrier around the S–N bond (Δ G ≠ = 62–71 kJ mol −1) and a preferred solid state and solution conformation in which the N-alkyl groups are oriented opposite to the perfluorooctyl group to minimize steric crowding around the S–N bond. Several perfluoroalkanesulfonamides were synthesized from the corresponding perfluoroalkanesulfonylfluorides. The X-ray crystal structures of N-ethyl-perfluorooctane-1-sulfonamide and two other perfluoroalkanesulfonamides are described. ▪