product present in a significant quantity is acetophenone lt 3 whereas the n hydroxyphthalimide is easily recovered and recycled by distilling the acetonitrile which is reused and extracting with water the residual solution of hydroperoxide in ethylbenzene the procedure showed in example 1 is adopted without n hydroxyphthalimide the ethylbenzene conversion is of 15 with a selectivity of 30 to hydroperoxide 40 to acetophenone and 30 in alcohol the procedure showed in example 1 is adopted without acetaldehyde the ethylbenzene conversion is lt 5 the procedure showed in example 1 is adopted using propionaldehyde instead of acetaldehyde the ethylbenzene conversion is of 16 with a selectivity of 97 in hydroperoxide and 3 in acetophenone the procedure showed in example 1 is adopted at 80 u00b0 c using benzaldehyde instead of acetaldehyde the ethylbenzene conversion is of 17 with a selectivity in hydroperoxide and acetophenone of 95 and 5 respectively a solution of 40 mmoles of ethylbenzene 0 4 mmoles of n hydroxyphthalimide and 4 mmoles of benzaldehyde in 5 ml of acetone is stirred for 6 hours at 68 u00b0 c in an atmosphere of oxygen at ordinary pressure the ethylbenzene conversion is of 11 with a selectivity of 87 in hydroperoxide and 13 in acetophenone a solution of 2 of lauryl ester of 4 carboxylic acid of n hydroxyphthalimide and 2 of propionaldehyde in 5 ml of ethylbenzene is stirred for 24 hours at 60 u00b0 c in an atmosphere of oxygen at ordinary pressure the ethylbenzene conversion is of 11 with a selectivity in hydroperoxide and acetophenone of 90 and 10 respectively a solution of 200 mmoles 25 ml of ethylbenzene and 4 mmoles of n hydroxyphthalimide in 25 ml of acetonitrile is stirred for 6 hours at 60 u00b0 c in an atmosphere of oxygen.