the invention relates to the synthesis of 1 , 1 , 2 , 2 - tetrahydroperfluoroalkanols and their esters by oxidizing a 2 - ethyl iodide using hydrogen peroxide in a carboxylic acid or carboxylic acid ester in the presence of sulphuric acid . in the process according to the invention , from 1 to 30 moles of sulphuric acid , from 1 to 50 moles of carboxylic acid or of an ester of such an acid , and from 3 to 20 moles of hydrogen peroxide per mole of 2 - perfluoralkyl ) ethyl iodide are used .