ISSN:
0538-8066
Keywords:
Chemistry
;
Physical Chemistry
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The flash photolysis of azo-n-propane and of azoisopropane has been studied by kinetic spectroscopy. Transient absorption spectra in theregion of 220-260 nm have been assigned to the n-propyl and isopropyl radicals. For the n-propyl radical, ∊max = 744 ± 39 l/mol cm at 245 nm and the rate constants for the mutual reactions were measured to be kc = (1.0 ± 0.1) × 1010 l/mol sec (combination) and kd = (1.9 ± 0.2) × 109 l/mol sec (disproportionation). For the isopropyl radical, ∊max = 1280 ± 110 l/mol cm at 238 nm, with kc = (7.7 ± 1.6) × 109 l/mol sec and kd = (5.0 ± 1.2) × 109 l/mol secThe rate constant for the dissociation of the vibrationally excited triplet state of the azopropanes into radicals was measured from the variation in the quantum yield of radicals with pressure. For azo-n-propane kdT = (6.6 ± 1.3) × 107 sec-1, and for azoisopropane kdT = (1.6 ± 0.4) × 108 sec-1. Collisional deactivation of the vibrationally excited singlet and triplet states was found to occur on every collision for n-pentane; but nitrogen and argon were inefficient with a rate constant of 1.1 × 1010 l/mol sec.Spectra observed in the region of 220-260 and 370-400 nm areattributed to the cis isomers of the parent trans-azopropanes. These are formed, as permanent products, in increasing amounts as the pressure is increased.
Additional Material:
10 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/kin.550130404
