The invention relates to a new process for the preparation of 1-bromoalkyl hydrocarbyl carbonates.The carbonates according to the invention are prepared by reacting an alpha-chlorinated carbonate of formula ##STR1## with an anhydrous brominated compound of formula ZBr in which Z represents hydrogen, the group (CH.sub.3).sub.3 -Si-, the group ##STR2## or bromine if R.sub.2 is other than an aromatic radical, in the presence of a catalyst chosen from the group consisting of heteroaromatic amines, quaternary ammonium or phosphonium halides, hexasubstituted guanidinium halides, alkaline earth metal halides or alkali metal halides in combination with a complexing agent for their cation.The carbonates according to the invention find their preferential applications as blocking agents for some antibiotics or as agents for the synthesis of phosphorus-containing carbonates which can be used as insecticides.