Rate constants for the reactions of the borate radical B(OH)3O{minus sign, dot below} with various para-substituted benzoic acids were measured by flash kinetic spectrophotometry. The product analyses and kinetic studies are consistent with an electron transfer mechanism followed by decarboxylation. In the case of the p-aminobenzoate anion the -NH2 and -COO- groups react simultaneously with the borate radical providing two parallel pathways with different rate constants. © 1990.