FIELD: chemical industry. SUBSTANCE: described is preparation of acetic acid and derivatives thereof by isomerization of methyl formate in the presence of water, aliphatic C1-C10 carboxylic acid as solvent, and catalyst system. Catalyst system comprises one iodide promoter and one iridium-based compound. Process is carried out in the presence of carbon monoxide partial pressure of which is maintained from 0,1•105 Pa to 25•105 Pa at 150-250 C. Amount of methyl formate in reaction mixture is maintained at less than 20 wt.%. EFFECT: greater process efficiency. 14 cl, 1 ex
