Premium
CALCULATED RATES AND EQUILIBRIA OF THERMAL INTERCONVERSION OF TRIPLET (3 g ‐ ) AND SINGLET ( 1 Δ g and g + ) MOLECULAR OXYGEN
Author(s) -
Mendenhall G. David
Publication year - 1978
Publication title -
photochemistry and photobiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.818
H-Index - 131
eISSN - 1751-1097
pISSN - 0031-8655
DOI - 10.1111/j.1751-1097.1978.tb06953.x
Subject(s) - reaction rate constant , excited state , chemistry , singlet state , singlet oxygen , catalysis , oxygen , thermal , thermal equilibrium , solvent , equilibrium constant , atomic physics , analytical chemistry (journal) , kinetics , thermodynamics , physics , quantum mechanics , organic chemistry , biochemistry , chromatography
— From spectroscopic data and rate constants in the literature, equilibrium constants and rates of thermal formation of singlet oxygen ( 1 Δ g and 1 Σ g + ) were calculated for a number of conditions. For the gas phase we estimate K eq ( 1 Δ g 3 Σ g ‐ ) = 1.67 exp(‐94.31 KJ/RT) and K eq ( 1 Σ g + / 3 Σ g ‐ ) = 0.33 exp(‐157.0 KJ/RT). The calculated rate constants for the 3 Σ g + → 1 Δ g transition of O 2 at 25°C varied from 2.5 × 10 ‐11 s ‐1 in water to 4.8 × 10 ‐16 s ‐1 in air, assuming equal solvent interactions with the ground and excited states. Physical quenchers for singlet oxygen are expected to be catalysts for its thermal formation. Equations are presented which allow one to estimate whether such catalysis by quenchers will result in a pro‐oxidant effect.