Structural aspects of the solid state polycondensation reactions of alkali 4-halogenomethylbenzoates

Sodium and potassium salts of 4-halogenomethylbenzoic acids undergo a polymerization reaction in the solid state upon heating. The reaction products are the corresponding alkali halide (NaCl, KCl, NaBr, KBr) and poly(4-hydroxymethylbenzoic acid). Solid-state C-13 NMR spectroscopy was used to characterize parent compounds and reaction products. Lithium 4-chloromethylbenzoate and lithium 4-bromomethylbenzoate do not undergo this reaction, and the underlying structural reasons can be understood on the basis of the crystal structures of these materials, which have been determined directly from synchrotron X-ray powder diffraction data. The sodium and potassium compounds could be obtained only as a microcrystalline mixture of polymorphs, a fact that rendered structure determination impossible. (C) 2001 Academic Press.