AbstractThis work deals with the modification reaction of dextran with 2‐acetoxybenzoyl chloride (acetylsalicyloyl chloride) using tertiary amines as catalyst/acceptor systems and the DMF/LiCl system as solvent. The structure of the resulting polymers was determined by means of IR,1H and13C NMR spectroscopy. Transesterification reactions were observed when 4‐dimethylaminopyridine or pyridine were used as catalysts, with the formation of acetoxy, 2‐hydroxybenzoyloxy (salicyloyloxy) and 2‐acetoxybenzoyloxy (acetylsalicyloxy) groups. When triethylamine was used as catalyst, only acetylsalicyloyloxy groups were found to be grafted onto the polymer chain. A linear dependence of the reaction rate on the concentrations of polymer, acetylsalicyloyl chloride and triethylamine was found. The activation energy was found to be 13,8