Deuterium kinetic isotope effect, D-KIE, for oxidation of perdeuteriated sodium butyrate, CD₃(CD₂)₂COONa, with manganate in the aqueous solution of 3 M NaOH has been determined in the temperature range 323-373 K. The temperature dependent k_H/k_D ratios are in the range from 17.59 at 323 K to 11.25 at 373 K. The activation energy difference, DQ_o = Q_oDD - Q_oHH = DH^#_oDD - DH^#_oHH = 9.20 kJ mol^-1, and the Arrhenius preexponential factors ratio A_oDD/A_oHH is equal to 1.76, corresponding to DS^ą_oDD - DS^ą_oHH = 4.70 J K^-1 as deduced from the Arrhenius and Eyring diagrams. This is the main evidence of tunnelling in the transfer of methylene hydrogens of butyrate to the negatively charged oxygens of manganate in very basic solutions. The k_oHH/k_oDD ratios, corrected for the ionic strengh, have been reproduced by multiplying the (k_C-H/k_C-D)KIE value, caused by zero point energy differences, by the Bell tunnel correction Q_tHH/Q_tDD. The half width of the energy barrier, as approximated by an inverted parabola, was found to be equal to 5·10^-11 m. The physicochemical origin of the energy barrier for the oxidation of n-chain aliphatic carboxylates with MnO₄^2- ions in strongly alkaline solutions has been discussed. The mechanisms of the permanganate versus manganate oxidation i.e., in acidic versus alkaline media are compared.