R. Zils, Direct determination of the equilibrium constant and thermodynamic parameters in the reaction of pentadienyl radicals with O-2, CR AC S IIC, 3(8), 2000, pp. 667-674
Citations number
26
Categorie Soggetti
Chemistry
Journal title
COMPTES RENDUS DE L ACADEMIE DES SCIENCES SERIE II FASCICULE C-CHIMIE
Reaction of pentadienyl radicals (C5H7) with O-2 has been studied by combin
ation of pulsed laser photolysis and photoionization mass spectrometry. The
se radicals could be generated either by the photolysis of 1.3-pentadiene o
r by the two-step reaction of carbon tetrachloride photolysis followed by t
he H-atom abstraction reaction of Cl atom with 1,4-pentadiene. The equilibr
ium between pentadienyl radicals, O-2 and pentadienylperoxy radicals could
be observed over the range 268-308 K. An analysis of the temporal signal of
pentadienyl radicals was used to evaluate the equilibrium constant. Third-
law analysis was used to evaluate the enthalpy change for the reaction C5H2
+ O-2 reversible arrow C5H-O-2. The observed C-O bond energy in the C5H7-O
-2 adduct was found to be 56.0 +/- 2.2 kj.mol(-1) which is lower than the v
alues of peroxy radicals formed with allyl and cyclohexenyl radicals which
have an allylic resonance structure. (C) 2000 Academie des sciences/Edition
s scientifiques et medicales Elsevier SAS.