Theoretical study of the peroxy radicals RO2 self-reaction: Structures and stabilization energies of the intermediate RO4R for various R

✍ Scribed by F. Bohr; E. Henon; I. García; M. Castro

• Publisher: John Wiley and Sons
• Year: 1999
• Tongue: English
• Weight: 176 KB
• Volume: 75
• Category: Article
• ISSN: 0020-7608
• DOI: 10.1002/(sici)1097-461x(1999)75:4/5<671::aid-qua34>3.0.co;2-n

✦ Synopsis

We have determined the lowest-energy structures of the RO 2 wR CH -, CH -CH -, CH -CH -CH -, CH -CH -CH -CH -,

x CH -CH CH-, and CH CH-CH -peroxy radicals. Further, the self-reaction 3 2 2 of these peroxyls may produce RO R tetroxide adducts, for which the influence of the 4 nature of R on their structure and stability was examined. These studies were done using theoretical calculations, of the all-electron type, performed at the MP2, DFT, and HF᎐DFT Ž . levels of theory. All calculations optimization, frequencies, and total energies were done using 6-31G** basis sets for each method. In all cases, we used HF frequencies on the MP2 geometry to compute Gibbs free energy from MP2 energy. DFT calculations were done using the BLYP functional, while for HF᎐DFT, the B3LYP scheme was used. Our main findings for RO are the following: The three methods provide rather similar 2 distances and angles. The O-O distance does not change significantly with increasing the size of R and with the branching, but it is more sensitive when a double bond is immediately neighboring. The C-O distance is more sensitive to the kind of R. Concerning the R O R adducts, they were located as local minima, that is, they behave a 4 b as intermediates. It was found that there is a dissymmetry between the structural parameters of the peroxy ''a'' and those of ''b.'' The O-O distances of peroxy increase by more than 0.1 A when going from the isolated peroxy to the intermediate. Similarly, the

C-O

distances show a decrease of about 0.02᎐0.03 A. In the searched RO R intermediates,