The Stability of α-Hydroperoxyalkyl Radicals.

High-level ab initio and Born-Oppenheimer molecular dynamic calculations have been carried out on a series of hydroperoxyalkyl (α-QOOH) radicals with the aim of investigating the stability and unimolecular decomposition mechanism into QO+OH of these species. Dissociation was shown to take place through rotation of the C−O(OH) bond rather than through elongation of the CO−OH bond. Through the C−O(OH) rotation, the unpaired electron of the radical overlaps with the electron density on the O−OH bond, and from this overlap the C=O π bond forms and the O−OH bond breaks spontaneously. The CH2OOH, CH(CH3)OOH, CH(OH)OOH, and α-hydroperoxycycloheptadienyl radical were found to decompose spontaneously, but the CH(CHO)OOH has a decomposition energy barrier of 5.95 kcal mol−1 owing to its steric and electronic features. The systems studied in this work provide the first insights into how structural and electronic effects govern the stabilizing influence on elusive α-QOOH radicals. [ABSTRACT FROM AUTHOR]