Process for the synthesis of racemic thioctic acid comprising the following stages: a) reaction of the alkyl ester of 6,8-di-halo-octanoic acid in an organic solvent with an aqueous solution of alkali disulfide in presence of a compound for phase transfer catalysis selected from the group consisting of quaternary ammonium or phosphonium salts having the following general formula: where: A is nitrogen of phosphorus, X is selected from the group consisting of Cl, Br, I, HSO4, and H2PO4 and the substitutents R1, R2, R3 and R4 are selection from the group consisting of linear or branched alkyl radicals having one to twenty carbon atoms (C1-C20), said substituents being identical or different one from the other, or only one of said substituents is selected from the group consisting of arylalkyl radicals having the following formula —(CH2)nC6H5 in which n=1-16; b) followed by the hydrolysis of the ester of racemic thiotic acid.