Structure–reactivity relationships for the self- reactions of linear secondary alkylperoxy radicals: An experimental investigation
✍ Scribed by A. A. Boyd; E. Villenave; R. Lesclaux
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 187 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0538-8066
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✦ Synopsis
The self-reactions of the linear pentylperoxy (C 5 H 11 O 2 ) and decylperoxy (C 10 H 21 O 2 ) radicals have been studied at room temperature. The technique of excimer laser flash photolysis was used to generate pentylperoxy radicals, while conventional flash photolysis was used for decylperoxy radicals. For the former, the recombination rate coefficients were estimated for the primary 1-pentylperoxy isomer (n-C 5 H 11 O 2 ) and for the secondary 2-and 3pentylperoxy isomers combined (Љsec-C 5 H 11 O 2 Љ) by creating primary and secondary radicals in different ratios of initial concentrations and simulating experimental decay traces using a simplified chemical mechanism. The values obtained at 298 K were:
- ϫ 10 Ϫ14 cm 3 molecule Ϫ1 s Ϫ1 . Quoted errors are 1, whereas the total relative combined uncertainties correspond to an estimated uncertainty factor around 1.65. For decylperoxy radicals, the kinetics of all the types of secondary peroxy isomers reacting with each other were considered equivalent and grouped as sec-C 10 H 21 O 2 (as for sec-C 5 H 11 O 2 ). The UV absorption spectrum of these secondary radicals was measured, and the combined self-reaction rate coefficients then derived as: k(sec-C 10 H 21 O 2 ϩ sec-C 10 H 21 O 2 ) ϭ (9.4 Ϯ 1.3) ϫ 10 Ϫ14 cm 3 molecule Ϫ1 s Ϫ1 at 298 K. Again, quoted errors are 1 and the total uncertainty factor corresponds to a value around 1.75. The sec-dodecylperoxy radical was also investigated using the same procedure, but only an estimate of the rate coefficient could be obtained, due to aerosol formation in the reaction cell: k(sec-C 12 H 25 O 2 ϩ sec-C 12 H 25 O 2 ) Ϸ 1.4 ϫ 10 Ϫ13 cm 3 molecule Ϫ1 s Ϫ1 , with an uncertainty factor of about 2. Despite the fairly high uncertainty factors, a relationship has been identified between the room-temperature rate coefficient for the selfreaction and the number of carbon atoms, n, in the linear secondary radical, suggesting: log(k(sec-RO 2 ϩ sec-RO 2 )/cm 3 molecule Ϫ1 s Ϫ1 ) ϭ Ϫ13.0-3.2 ϫ exp(Ϫ0.64 ϫ (n-2.3)).