Nitroxyl derivatives of 5-fluorineuracil of the general formula (I) having an antitumoral activity.

In addition to carbon dioxide, nitrate ions and nitronium ions are formed, said ions comprising electrophiles which are necessary for nitration.

3 of nitryl perchlorate with benzene gave a slight explosion and flash.

In the formula, R is H, hydroxyl, halogen, C1-C12 alkyl, C1-C12 alkoxyl, nitryl, carboxyl; and R is on the optional place in the benzene ring.

A brown colouration and precipitated silver chloride display the formation of the carbonic acid reactants, said brown colouration rapidly discolouring due to an immediate reaction of the nitronium ions with the substrate with is to be nitrated.

The transparent film contains (A) a thermoplastic resin having a substituted and/or unsubstituted imide group at a side chain and (B) a thermoplastic resin having a substituted and/or unsubstituted phenyl group and a nitryl group.

The nitronium-containing reactant may be a covalently bonded compound containing an NO2-group; a nitryl halide; or a nitronium salt having the formula (NO2+)qX-q, where X is the anion of the nitronium salt and q = 1-2.