Processes for alkylating hydroxyaryl compounds by reacting a hydroxyaryl with at least one olefin of a complex hydrocarbon stream. The complex hydrocarbon stream preferably comprises a fraction of a cracked hydrocarbon feed stream or the reaction products of a dehydrogenation of a paraffinic feedstock. The olefin of the complex hydrocarbon stream is preferably a branched olefin, e.g., isobutylene or isoamylene. The alkylated compositions are suitable for forming liquid phosphite compositions.