Carbon-13 kinetic isotope effect in the oxidation of liquid formic acid with uranium peroxide

Carbon-13 kinetic isotope effects in the oxidation of liquid formic acid (FA) with uranium peroxide, UO4, have been studied between 20-120 degrees C. The C-13 KIE's, laying in the range 1.016-1.026, indicate that the full splitting of the C-13-H-1 bond takes place in the transition state of this oxidation process. The calculations considering one C-H coordinate only reproduce well the experimental C-13 KIE values. At room temperature the experimental C-13 KIE = 1.0266 is slightly higher than the calculated 1.0221/20 degrees C, obtained considering only one stretching vibration C-13-H-1, but it is quite close to the C-13 KIE observed in the enzymic decarboxylation of FA equal 1.0260. The mechanism of reaction of liquid FA with UO4 has been proposed.