A persistent hexabromonaphthalene isomer is 2, 3, 4, 5, 6, 7‐hexabromonaphthalene

Polybrominated biphenyl (PBB) mixtures are contaminated with brominated naphthalenes formed during the synthesis procedure. Synthesis of hexabromonaphthalenes (HBNs) by direct bromination of naphthalene results in a mixture of two isomers. The identity of the major isomer, 1,2,3,4,6,7-HBN, was previously confirmed (Birnbaum et al., 1983). The minor isomer is definitively identified as 2,3,4,5,6,7-HBN by high-field nuclear magnetic resonance (NMR) spectroscopic analysis of brominated [1-13C]naphthalene-derived products. This isomer is extremely persistent and can be isolated from the liver of rats 10 d after treatment with the HBN mixture by a combination of solvent extraction and partition and adsorption chromatography.