Kinetics of formation, dissociation, and redox reactions of the benzyl radical‐Cu(II) ion complex in a 10% acetonitrile‐90% water mixture

The rate constant of formation, dissociation, and redox reaction of the benzyl radical‐copper(II) ion complex have been determined at temperatures from 274 K to 333 K by laser flash photolysis of 1,3‐diphenyl‐2‐propanone (DBK) in a 10% acetonitrile‐90% water mixture containing copper(II)perchlorate. Rate constants were calculated from time resolved absorbances of both benzyl radicals (Bz) at 315 nm and benzyl‐copper complexes (BzCu 2+ ) at 375 nm. Values of the rate constants of the formation of BzCu 2+ complex were fitted to the equation\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_3/{\rm dm}^3\, {\rm mol}^{- 1}\, {\rm s}^{- 1} = (7.94 \pm 0.05)-[(3.1 \pm 0.3)\,{\rm kJ\, mol}^{- 1} /2.303{\rm}\, RT] $$\end{document} and the rate constant of the reverse reaction of BzCu 2+ complex to the equation\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_4 /{\rm s}^{-1} = (7.58 \pm 0.05) - [(7.0 \pm 0.7){\rm kJ\, mol}^{-1} /2.303{\rm}\,RT] $$\end{document} The rate constant of the redox reaction of BzCu 2+ complex to benzyl alcohol and copper(I) ion can be described by the equation\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_5 /{\rm s}^{-1} = (6.61 \pm 0.1) - [(6.0 \pm 0.5){\rm kJ\, mol}^{-1} /2.303{\rm}\,RT] $$\end{document} The first order rate constant of dissociation of phenylacetyl radical formed initially in the flash photolysis of DBK is given by the equation\documentclass{article}\pagestyle{empty}\begin{document}$$ \log k_2 /{\rm s}^{-1} = (9.58 \pm 0.04) - [(19.5 \pm 0.8){\rm kJ\,mol}^{-1} /2.303{\rm}\,RT] $$\end{document}