Photosensitized dissociation of di-tert-butyl peroxide. Energy transfer to a repulsive excited state
Abstract
Energy transfer from a variety of aromatic hydrocarbons and ketones to di-tert-butyl peroxide has been examined by using nanosecond laser flash photolysis techniques. Triplet energy transfer to the peroxide leads to its efficient cleavage into two tert-butoxy radicals. Representative rate constants for triplet quenching in benzene at 25/sup 0/C are 7.9 x 10/sup 6/, 3.4 x 10/sup 6/, and 7.0 x 10/sup 4/M/sup -1/s/sup -1/ for p-methoxypropiophenone, benzophenone, and benz(a)anthracene, respectively. The rate of transfer for p-methoxypropiophenone (E/sub T/ = 72.5 kcal/mol) is approximately temperature independent; for lower energy sensitizers ca. 0.17 kcal/mol activation energy is required for each kilocalorie per mole decrease in triplet energy. No evidence indicating exciplex intermediacy was found. A model for energy transfer to a repulsive state of the peroxide is proposed in which no activation energy is required if the sensitizer meets the energy requirements at the 0-0 equilibrium distance. For sensitizers of lower triplet energy, energy transfer to a repulsive state is proposed to occur from a thermally activated ground state having a greater than equilibrium oxygen-oxygen bond length. The same mechanism may apply in other systems where the acceptor lacks low-lying excited states. A few rate constants for the quenching of singletmore »
- Authors:
- Publication Date:
- Research Org.:
- Univ. of Notre Dame, IN
- OSTI Identifier:
- 6875577
- Resource Type:
- Journal Article
- Journal Name:
- J. Am. Chem. Soc.; (United States)
- Additional Journal Information:
- Journal Volume: 103:3
- Country of Publication:
- United States
- Language:
- English
- Subject:
- 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; AROMATICS; ENERGY TRANSFER; KETONES; PEROXIDES; PHOTOLYSIS; BENZOPHENONE; FLUORESCENCE; LASER RADIATION; RADICALS; SCINTILLATION QUENCHING; TRIPLETS; CHEMICAL REACTIONS; DECOMPOSITION; ELECTROMAGNETIC RADIATION; LUMINESCENCE; MULTIPLETS; ORGANIC COMPOUNDS; OXYGEN COMPOUNDS; PHOTOCHEMICAL REACTIONS; RADIATIONS; 400500* - Photochemistry
Citation Formats
Scaiano, J C, and Wubbels, G G. Photosensitized dissociation of di-tert-butyl peroxide. Energy transfer to a repulsive excited state. United States: N. p., 1981.
Web. doi:10.1021/ja00393a024.
Scaiano, J C, & Wubbels, G G. Photosensitized dissociation of di-tert-butyl peroxide. Energy transfer to a repulsive excited state. United States. https://doi.org/10.1021/ja00393a024
Scaiano, J C, and Wubbels, G G. 1981.
"Photosensitized dissociation of di-tert-butyl peroxide. Energy transfer to a repulsive excited state". United States. https://doi.org/10.1021/ja00393a024.
@article{osti_6875577,
title = {Photosensitized dissociation of di-tert-butyl peroxide. Energy transfer to a repulsive excited state},
author = {Scaiano, J C and Wubbels, G G},
abstractNote = {Energy transfer from a variety of aromatic hydrocarbons and ketones to di-tert-butyl peroxide has been examined by using nanosecond laser flash photolysis techniques. Triplet energy transfer to the peroxide leads to its efficient cleavage into two tert-butoxy radicals. Representative rate constants for triplet quenching in benzene at 25/sup 0/C are 7.9 x 10/sup 6/, 3.4 x 10/sup 6/, and 7.0 x 10/sup 4/M/sup -1/s/sup -1/ for p-methoxypropiophenone, benzophenone, and benz(a)anthracene, respectively. The rate of transfer for p-methoxypropiophenone (E/sub T/ = 72.5 kcal/mol) is approximately temperature independent; for lower energy sensitizers ca. 0.17 kcal/mol activation energy is required for each kilocalorie per mole decrease in triplet energy. No evidence indicating exciplex intermediacy was found. A model for energy transfer to a repulsive state of the peroxide is proposed in which no activation energy is required if the sensitizer meets the energy requirements at the 0-0 equilibrium distance. For sensitizers of lower triplet energy, energy transfer to a repulsive state is proposed to occur from a thermally activated ground state having a greater than equilibrium oxygen-oxygen bond length. The same mechanism may apply in other systems where the acceptor lacks low-lying excited states. A few rate constants for the quenching of singlet sensitizers have also been determined by using fluorescence techniques.},
doi = {10.1021/ja00393a024},
url = {https://www.osti.gov/biblio/6875577},
journal = {J. Am. Chem. Soc.; (United States)},
number = ,
volume = 103:3,
place = {United States},
year = {Wed Feb 11 00:00:00 EST 1981},
month = {Wed Feb 11 00:00:00 EST 1981}
}