THERMAL-STABILITY OF ALIPHATIC-AROMATIC POLYAMIDE MODEL COMPOUNDS - STRUCTURE-REACTIVITY RELATIONSHIPS IN THE CATALYZED THERMAL-REACTION OFBENZAMIDES IN THE PRESENCE OF COPPER HALIDES

The relationship between the structure and reactivity of aliphatic-aro matic polyamides in the presence of CuI in an inert atmosphere was pro bed by reacting a family of benzamides with varying degrees of substit ution on the amide nitrogen. Experiments with benzamide, N-methylbenza mide, N,N-dimethylbenzamide, N-hexylbenzamide, and N,N-dihexylbenzamid e allowed comparison of primary, secondary, and tertiary benzamides an d identification of the degradation pathways influenced by CuI. The pr esence of copper iodide enhanced the reactivity of all of the benzamid es. Loadings as low as 0.5% led to higher conversion and increased rec overable product yields. Reaction path selectivities were also affecte d by the addition of CuI. The selectivity to benzene increased for all reactants, and the pathway leading to N-alkylation increased for the reaction of NHB. In all, these results revealed three major reaction p athways influenced by CuI: 1) N-C bond cleavage; 2) N-H bond cleavage; and 3) removal of the amide functional group from the aromatic ring. Kinetic results and visible color changes suggested a direct interacti on of CuI with the reactant benzamide. Three electron-rich sites on th e reactant benzamide, namely, the lone pairs on the carbonyl oxygen, t he lone pair on the amide nitrogen and the aromatic ring, are likely s ites of interaction of Cu+. Models invoking the subsequent reaction of complexes formed from Cu+ ion interaction at each of these sites acco unt for the observed products well. (C) 1997 John Wiley & Sons, Inc.