C6, C7, and C8 perfluoroalkyl-substituted phosphinic acids

Abstract

Reaction of red phosphorus with R(f)I a 1:2 molar ratio at 230 °C led to the formation of a mixture of (R(f))2PI. and (R(f))PI2 (R(f) = C6F13, C7F15, C8F17) in about a 70:30 ratio, respectively. These mixtures were separated by vacuum distillation. (R(f))2PI (R(f) = C6F13; C7F15) are yellow liquids whereas (C8F17)2PI is a yellow solid. Oxidation of (R(f))2PI with excess NO2 led to (R(f))2P(O)OH (R(f) = C6F13, C7F17, C8F17) in >90% isolated yields after aqueous hydrolysis of the anhydride intermediates. These highly fluorinated phosphinic acids are white solids with sharp melting points and are highly soluble in methyl sulfoxide (DMSO) and 1,1,2-trichlorotrifluoroethane. However, solubility in chloroform and methylene dichloride is low. These perfluoroalkylphosphinic acids were characterized by IR, NMR (1H, 19F, and 31P), and mass spectra and elemental analysis.