Substituted benzonitriles and compositions useful for bleaching

A composition useful for bleaching, comprising:

• (a) an aromatic bleach precursor the aromatic ring of which is substituted by at least one cyano group and additionally with at least one electron-withdrawing group other than cyano, wherein the electron-withdrawing group is selected from group (i) or group (ii), wherein group (i) is ##STR4## where R.sub.1, R.sub.2 and R.sub.3 are C.sub.1-20 alkyl, C.sub.1-20 alkyl aryl, or at least two of R.sub.1, R.sub.2, or R.sub.3 joined to form a heterocycle;
• and where group (ii) is halo, nitro, sulfonic acid, sulfonyl chloride, sulfonate ester, carboxylate ester, or aryl substituted with one or more of halo, nitro, sulfonic acid, sulfonyl chloride, sulfonate ester, or carboxylate ester;
• wherein when there is only one cyano group substituted on the aromatic ring of the precursor and when the electron-withdrawing group is selected from group (ii), then there are at least two of such electron-withdrawing groups selected from group (ii);
• and,
• (b) a peroxygen source, wherein the peroxygen attacks the precursor at the cyano group to provide the bleaching species.