F-19 NMR INVESTIGATION OF AROMATIC AMIC ACID AND IMIDE MODEL COMPOUNDS .1.

Several fluorinated aromatic amic acid and imide model compounds and t heir intermediates were prepared and investigated in N-methylpyrrolidi none by F-19 and C-13 n.m.r. Starting materials included 4-fluoroanili ne, 3-fluorophthalic anhydride, 2,2-bis(3,4-carboxyphenyl)hexafluoropr opane dianhydride and 2,2-bis(4-aminophenyl)hexafluoropropane. The adv antages of F-19 n.m.r. for studying amic acid and imide chemistry were numerous. Anhydride and amine starting materials, as well as amic aci d, isoimide and imide compounds, were easily identified in the F-19 n. m.r. spectra. Isomeric contents of amic acid mixtures were directly me asurable. Many unique aspects of polyimide chemistry, such as amic aci d equilibria and imide interchange reactions, could be quantitatively identified. Data from C-13 n.m.r. and F-19 n.m.r. were related in many cases, as were the carbon-fluorine coupling constants.