Structural aspects of the solid-state polycondensation reaction in alkali 4-halogenomethylbenzoates

Sodium and potassium salts of 4-halogenomethylbenzoic acids undergo a polym erization reaction in the solid state upon heating. The reaction products a re the corresponding alkali halide (NaCl, KCl, NaBr, KBr) and poly(4-hydrox ymethylbenzoic acid). Solid-state C-13 NMR spectroscopy was used to charact erize parent compounds and reaction products. Lithium 4-chloromethylbenzoat e and lithium 4-bromomethylbenzoate do not undergo this reaction, and the u nderlying structural reasons can be understood on the basis of the crystal structures of these materials, which have been determined directly from syn chrotron 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.