C-6, C-7, and C-8 perfluoroalkyl-substituted phosphinic acids

Reaction of red phosphorus with RfI in a 1:2 molar ratio at 230 degrees C l ed to the formation of a mixture of (Rf)(2)PI and (R-f)PI2 (R-f = C6F13, C7 F15, C8F17) in about a 70:30 ratio, respectively. These mixtures were separ ated by vacuum distillation. (Rf)2PI (Rf = C6F13, C7F15) are yellow liquids whereas (C8F17)2PI is a yellow solid. Oxidation of (R-f)(2)PI with excess NO2 led to (R-f)(2)P(O)OH (R-f = C6F13, C7F15, C8F17) in >90% isolated yiel ds after aqueous hydrolysis of the anhydride intermediates. These highly fl uorinated phosphinic acids are white solids with sharp melting points and a re highly soluble in methyl sulfoxide (DMSO) and 1,1,2-trichlorotrifluoroet hane. However, solubility in chloroform and methylene dichloride is low. Th ese perfluoroalkylphosphinic acids were characterized by IR, NMR (H-1, F-19 , and (31)p) and mass spectra and elemental analysis.