Effect of Solvent Polarity on Bromobutyl Rubber Isomerization

Abstract

The reaction pathway of the isomerization in the process of butyl rubber bromination was proposed based on density functional theory (DFT) and MP2 calculations with the 6-31+G(d) basis set. The microstructural composition of the brominated butyl rubber was determined via proton nuclear magnetic resonance spectroscopy (1H-NMR).The transition state of isomerization reaction was identified. The geometries of the reactant, transition state, and product structures were optimized. The effect of solvation on model compounds was simulated using the polarizable continuum model (PCM). The energy barriers for isomerization reactions were calculated with different solvents (vacuum, n-hexane, and 245/105 mL n-hexane/dichloromethane (DCM) mixture). The increase in solvent polarity decreased the activation energy and facilitated the isomerization reaction. This finding was consistent with the experimental result.