Kinetic studies on the Menschutkin reaction of dimethylamino‐terminated poly(oxytetramethylene) with halides

Abstract

AbstractThe kinetics of the Menschutkin reaction between dimethylamino‐terminated poly(oxytetramethylene) [AT‐PT (1), molecular weight 1160] and dihalides was followed by means of 1H NMR spectroscopy of NCH3 protons. For comparison, low‐molecular‐weight monoamines were subjected to similar experiments. No difference was found between the second‐order rate constants of AT‐PT and those of monoamines. But the rate constants depend on the kind of halide, i.e., the bromides [1,4‐bis(bromomethyl)benzene, 1,4‐dibromo‐2‐butene, benzyl bromide, allyl bromide] are much more reactive than the corresponding chlorides. Different from the usual nucleophilic reactions, the rate in a polar solvent (methanol) is smaller than that in the non‐polar chloroform. According to the activation parameters, this anomaly is due to hydrogen bonding, which has to be broken for the reaction to occur in a polar protic solvent.