| Abstract
| - The reduction of Tempol by ascorbic acid in concentrated sucrose solutions was measured by electronparamagnetic resonance (EPR) at temperatures ranging from 16 to −16 °C. This method allowedthe determination of the rate constants (k) of this fast reaction, by recording the Tempol reduction asa function of time. The two reactants were initially separated and had to migrate for the reaction tooccur. The experimental findings were compared with predicted values according to the equation fordiffusion-controlled reaction proposed by Atkins. The experimental reaction rate constants wereobserved to be lower than the calculated ones. However, the experimental values were found to becontrolled by the temperature and viscosity changes of the reaction media, as expected for a diffusion-controlled reaction. Keywords: Vitamin C; Tempol; electron paramagnetic resonance; negative temperatures; reaction;cryoconcentration; diffusion
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