2,5,6,9,10-Pentabromocyclododecanols (PBCDOHs): a new class of HBCD transformation products

Pentabromocyclododecanols (PBCDOHs) are potential environmental transformation products of hexabromocyclododecanes (HBCDs). They are also potential stage one metabolites of biological HBCD transformations. Herein, we present analytical evidence that PBCDOHs are also constituents of technical HBCDs and flame-proofed polystyrenes (FP-PSs). PBCDOHs are possibly formed during the synthesis of technical HBCD, presumably during the bromination of cyclododecatrienes in aqueous isobutanol together with isobutoxypentabromocyclododecanes (iBPBCDs), which have been identified in these materials recently. Of the 64 stereoisomers possible, eight pairs of enantiomers, named α-, β-, γ-, δ-, ε-, ζ-, η-, and θ-PBCDOHs were separated with a combination of normal-, reversed- and chiral-phase LC. Crystal structure analysis revealed the stereochemistry of the α-PBCDOH pair of enantiomers, which was assigned to (1S,2S,5R,6S,9S,10R)-2,5,6,9,10-pentabromocyclododecanol and its enantiomer. Mass spectrometric data are in accordance with the expected isotope patterns. On a C(18)-RP-column, the polar PBCDOHs eluted before the HBCD and iBPBCD classes of compounds. PBCDOHs were also found in FP-PS materials. The stereoisomer patterns varied considerably in these materials like those of HBCDs and iBPBCDs. Expanded polystyrenes were rich in late-eluting stereoisomers, similar to technical HBCD mixtures. Extruded polystyrenes contained more of the polar, faster-eluting isomers. The presented chromatographic and analytical methods allow a stereoisomer-specific search for PBCDOHs in biota samples, which might have experienced metabolic HBCD transformation reactions. Besides this potential source, it has to be recognized that PBCDOHs are by-products in technical HBCDs and in flame-proofed polystyrenes. Therefore, it is likely that PBCDOHs and iBPBCDs are released to the environment together with HBCD-containing plastic materials.