Identification of chlorinated dimethoxystilbene isomers and homologues in bleached paper products

We report here the identification of a novel class of compounds, the chlorinated dimethoxystilbenes (pinosylvins), in bleached paper products. Pinosylvins are naturally occurring compounds in wood that deter infections and predators. These compounds are being chlorinated during the pulp bleaching process. Two dichlorinated pinosylvins have previously been identified in bleached paper pulp, but we have identified other isomers and more highly chlorinated homologues in various bleached paper products. These compounds are present at concentrations on the order of hundreds of ppb. On the basis of the mass spectra of synthesized standards, we can distinguish the isomers in which the chlorines are located on the ethylene moiety from those in which the chlorines are located on the aromatic ring with the methoxy groups. In addition, we can predict the chlorine substitution patterns on both rings for these compounds using linear relationships between retention indexes and calculated dipole moments. The toxicity of these compounds is not known; however, isomers related to the pesticide methoxychlor are proestrogenic.