Kinetics of the reaction between alkaline sulfides and aryl dichlorides — model study on 4‐chloro‐ and 4,4′‐dichlorobenzophenones

The kinetics of the reaction between alkaline sulfides and halogenated aromatic monomers was studied using lithium sulfide and 4‐chlorobenzophenone (1a) and 4,4′‐dichlorobenzophenone (1b) as models. The release of H 2 S from reaction medium and the possible formation of a compound between sulfide and N ‐methyl‐2‐pyrrolidone (NMP) during the preliminary dehydration step are key steps of the reaction. The reaction proceeds following two successive kinetic regimes: a first one where rapid second‐order reactions of sulfide and thiolate with 1a or 1b take place, and a second one where the slow release of sulfide from the compound formed during dehydration is rate determining and therefore governs the molecular weight of final polymer. A good agreement was found between theoretical curves calculated from this kinetic scheme and experimental data, indicating a polymerization mechanism based on an S N Ar reaction mechanism.