Abstract: A zinc electroplating bath comprising as a brightener additive a reaction product of an heterocyclic pentagonal or hexagonal compound with a cyclic carbonate; the ensuing product is then reacted with an epihalohydrin or an alpha-dihalohydrin which ensuing product is then reacted with a compound of the general formula ##STR1## wherein x represents a hydrogen atom or a phenyl radical;R.sub.1 represents an alkenylene, alkylene, haloalkenylene, hydroxyalkenylene or carboxy (hydroxy) alkenylene group; andR.sub.2 represents a hydrogen atom or an alkyl, hydroxyalkyl, haloalkyl or halohydroxyalkyl group.