The HOCH₂CH₂OO• and HOCH₂CH₂O• radicals are prototypes of species that possess intramolecular hydrogen bonds which enable intramolecular hydrogen shift reactions across those hydrogen bonds:

HOCH₂CH₂OO• → •OCH₂CH₂OOH (1)

HOCHRCH₂O• →•OCHRCH₂OH (2)

These types of reactions may play an important role in both the atmosphere and in combustion systems. We have used density functional theory and composite electronic structure methods determine that Reaction (1) has a barrier of 23.6 kcal/mol, and that Reaction (2) has a barrier of 22.7 kcal/mol. We used RRKM/master equation simulations to model the kinetics of chemically activated HOCH₂CH₂OO• formed in the reaction HOCH₂CH₂• + O₂; our calculations suggest that a majority of chemically activated HOCH₂CH₂OO• undergoes a prompt hydrogen shift reaction across the at pressures up to 10 Torr. This low pressure is relevant to many experiments.

Variational transition state theory (TST) calculations were carried out using the POLYRATE program. For Reaction 1 at 298 K, the variational TST rate constant is ~30% lower than the conventional TST result, and the μOMT method predicts that tunneling accelerates the reaction by a factor of 3. TST calculations on Reaction (2) reveal no variational effect. Tunneling is very important in Reaction (2); the 298 K μOMT transmission coefficient is 10⁵.