Singlet dioxygen lifetimes

Singlet Dioxygen Lifetimes in Various Solvents Solvent Lifetime ( xs) Solvent Lifetime (n-s)... 

Singlet dioxygen in biological systems is highly selective 2 is umeactive with most organic functional groups (e.g. saturated a bonds, simple alkenes, and carbonyl groups). In part, this is due to its limited lifetime (2 ts in H2 , 58 ps in H2 , 16 ps in DMF, 65 ps in MeCN, and 610 ps in d -MeCN), to its paired valence-electton shell, and to its... 

Much attention has been paid to the chemistry and biological chemistry of singlet dioxygen and superoxide ion. The lifetime of the former species, known to be solvent-dependent, is much increased for deuterated acetone, acetonitrile, benzene and chloroform compared to the undeuterated solvent. This is a remarkable solvent deuterium isotope effect. Electron transfer to 02 from tetramethylphenylenediamine to give superoxide has been confirmed, the rate of reaction being close to the diffusion-controlled limit. Kinetic studies on the photochemical formation of superoxide from jU-superoxodecacyanodicobalt(III) ions and oxygenated ethanol solutions have been reported. 

The fluorescence quantum yield of anthracene in degassed acetonitrile is 0.3. It is reduced by 30% upon admission of air. Estimate the lifetime of the singlet state of anthracene in degassed solution and the rate constant of fluorescence. Refer to Section 2.2.1. The concentration of dioxygen in air-saturated acetonitrile is 2x10 3m. [tj = 5.6 ns, kf = 5.4 x 107 s ]... 

Calculate the concentration required to quench 99% of singlet excited naphthalene, given that the lifetime of the naphthalene singlet state is 100 ns in the absence of dioxygen and A. /V-di methyl aniline and that the rate constant of diffusion /cdill is 5 x 109m 1 s [0.2m]... 

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