Rate constants for the bimolecular self‐reaction of tertbutyl radicals in nalkane solvents

Abstract

Rate constants for the self-reaction of tert-butyl radicals in six n-alkanes are determined as functions of temperature by kinetic electron-spin resonance spectroscopy and from rates of product formation. They are well described by a Smoluchowski-Stokes-Einstein treatment including effects of microfriction and spin statistical factors, indicating complete diffusion control. The ratio of disproportionation to combination products is found to depend on temperature and solvent. This is tentatively ascribed to reorientational effects in the encounter pairs.

The kinetics of the bimolecular sel‐reaction of t‐butyl radicals in solution. I. Termination rates

“…Further, it is probably not fully correct to cancel the hydrodynamic radius rA defined by SW (22d) against the half reaction distance p/2, since the r, of SW is slightly too large [86], especially at high temperatures. However, these effects change the calculated data given in [23] only little (< 15%), and do not affect the conclusions given there.…”

“…[23] are probably an artifact due to the SW model used in the analysis, since this treatment tends to underestimate the diffusion coefficients at elevated viscosities. Further, it is probably not fully correct to cancel the hydrodynamic radius rA defined by SW (22d) against the half reaction distance p/2, since the r, of SW is slightly too large [86], especially at high temperatures.…”

“…mol-I s-' at an effective temperature of 25°C was assumed as a relative standard value [23]. All rate constants given for other or conically tipped cylinders) was used for measurements of viscosities in the range 10< q < 100 mPa .…”

Rate constants for the reaction of tert‐butyl radicals with chloroform in solution

“…Our experimental arrangement for time-resolved ESR experiments with photochemical radical generation has been described in some detail previously [19][20][21][22]. For this work the following instrumental changes proved to be essential.…”

Photoreduction of IrCl62? complex in alcohol solutions and its reaction with hydroxyalkyl radicals

“…0.2 -10 cP As a rule, this equation is reported to hold for the diffusion-controlled reactions in low-viscous nonpolar solvents [39,40]. The anomalous character of diffusion constants is typical of the solvents with hydrogen bonds, such as alcohols [36,41 -43].…”