The Stability of α-Hydroperoxyalkyl Radicals

Josep M Anglada; Ramon Crehuet; Joseph S Francisco

doi:10.1002/chem.201604499

The Stability of α-Hydroperoxyalkyl Radicals

Chemistry. 2016 Dec 12;22(50):18092-18100. doi: 10.1002/chem.201604499. Epub 2016 Nov 3.

Authors

Josep M Anglada^{1

2}, Ramon Crehuet², Joseph S Francisco¹

Affiliations

¹ College of Arts and Sciences, University of Nebraska-Lincoln, 1223 Oldfather Hall, Lincoln, NE, 68588-0312, United States.
² Departament de Química Biològica i Modelització Molecular, IQAC-CSIC, c/Jordi Girona 18, 08034, Barcelona, Spain.

PMID: 27808436
DOI: 10.1002/chem.201604499

Abstract

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 CH₂ OOH, 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.

Keywords: ab initio calculations; atmospheric chemistry; density functional calculations; molecular dynamics; radicals.