Kinetics of the reaction of alkyl bromides with nucleophiles containing nitrogen atoms

Abstract

Kinetics of the reactions of propyl, propargyl and allyl bromides with anilines has been studied in methanol and dipolardmf. All reactions were found to be of second order. The values of the Bronsted slope (0–4) suggested that bond formation occurs to a considerable extent in the transition state. Electron-donating substituents increased the rate, while electron-withdrawing groups decreased the rate. The magnitudes of the negative values (≈1) indicate that the reaction rate depends on the availability of electron-density on the nitrogen atom, which implies bond formation, suggesting that all the reactions are SN² in nature, forming a loose transition state. Isokinetic temperature values calculated from the three methods for the reaction of allyl bromide-anilines suggested that the reaction series indmf is entropy controlled while in a methanol medium hydrogen bonding is responsible for the solute-solvent interactions.