Unravelling the ultrafast photodecomposition mechanism of dibenzoyl peroxide in solution by time-resolved IR spectroscopy.
The ultrafast photo-fragmentation of dibenzoyl peroxide (DBPO) is studied using femtosecond UV excitation at 266 nm and mid-infrared broadband probe pulses to elucidate the dissociation mechanism. With the help of (13)C-labeled DBPO it was possible to unambiguously assign transient IR bands in the fingerprint region to the benzoyloxy radical. Our experiments show that the fragmentation is controlled by the S(1)-lifetime of DBPO and within 0.4 +/- 0.2 ps leads to a benzoyloxy/phenyl radical pair plus CO(2)via concerted bond breakage of the O-O and the phenyl-C(carbonyl) bond. 20% of the radical pairs geminately recombine to phenyl benzoate on a timescale of 70 ps.
Reichardt
Christian
C
Abteilung Spektroskopie und Photochemische Kinetik, Max-Planck-Institut für Biophysikalische Chemie, 37070 Göttingen, Germany.
Schroeder
Jörg
J
Vöhringer
Peter
P
Schwarzer
Dirk
D
D001554:Benzene / Q000737:chemistry; D001555:Benzene Derivatives / Q000737:chemistry; D001585:Benzoyl Peroxide / Q000737:chemistry* / Q000528:radiation effects; D002245:Carbon Dioxide / Q000737:chemistry; D005609:Free Radicals / Q000737:chemistry; D008956:Models, Chemical; D010782:Photolysis; D013055:Spectrophotometry, Infrared / Q000379:methods*; D014466:Ultraviolet Rays
D001555:Benzene Derivatives; D005609:Free Radicals; D002245:Carbon Dioxide; D001554:Benzene; D001585:Benzoyl Peroxide