Cb. Roberts et al., LASER FLASH-PHOTOLYSIS INVESTIGATIONS OF DIFFUSION-CONTROLLED REACTIONS IN SUPERCRITICAL FLUIDS, Journal of physical chemistry, 97(21), 1993, pp. 5618-5623
Laser flash photolysis has been used to investigate the triplet-triple
t annihilation (TTA) process of benzophenone (Ph2C=O) and the self-ter
mination reaction of benzyl radical (PhCH2) in supercritical CO2 and e
thane. Kinetic measurements were performed at various pressures above
the critical pressure along two isotherms, one close to the critical t
emperature of the solutions (35-degrees-C) and one further removed (50
-degrees-C). The second-order rate constants obtained indicate that ea
ch reaction occurs at the diffusion limit when spin statistical factor
s are considered. No evidence of enhanced cage effects due to supercri
tical solvent clustering about diffusive encounter pairs or enhanced s
olute/solute interactions were observed in these experiments. Addition
ally, the photocleavage of dibenzyl ketone and the rate constants for
decarbonylation of phenylacetyl radical (PhCH2CO) have been examined u
nder the above conditions and do not show any anomalous behavior or ca
ge effects.