Trapping Activated Tautomerism of Acetophenone in Polyethylene

Polyethylene (PE) is an excellent electrical insulator, and is common in high voltage cable applications, where it is chemically cross linked to improve thermal stability, leaving cross linking residues in the material. Acetophenone is one such residue, which is often studied due to its tendency to trap mobile electrons. In the present work the keto-enol tautomerization of acetophenone in the gas phase is studied using quantum chemistry methods. Activation energies, free energy change and Eyring rate constants are calculated for both reaction directions, for both neutral and ionized acetophenone. Ionization is shown to lower the activation energies of tautomerization, and the energetically favored enol to keto reaction has particularly high reaction rates for ionized molecules. Activation energies are similar to electron trapping energies of acetophenone in PE, and we postulate a trapping activated tautomerization mechanism, and discuss how the various modes of trapping, de-trapping and recombination for keto and enol acetophenone may establish a balance keto and enol tautomers over time.