Synthesis and characterization of polybrominated diphenyl ethers - Unlabelled and radiolabelled tetra-, penta- and hexa-bromodiphenyl ethers

Abstract

Diphenyl ether, 3-bromodiphenyl ether and 3,3′-dibromodiphenyl ether have been synthesized via coupling of the appropriate phenol and bromobenzene. Each of these compounds was subsequently brominated to (i) 2,2′,4,4′-tetrabromodiphenyl ether, (ii) 2,2′,3,4,4′-pentabromodiphenyl ether and 2,2′,4,4′,5-pentabromodiphenyl ether and (iii) 2,2′,3,3′,4,4′-hexabromodiphenyl ether, 2,2′,3,4,4′,5′-hexabromodiphenyl ether and 2,2′,4,4′,5,5′-hexabromodiphenyl ether, respectively. The tetrabromodiphenyl ether and two pentabromodiphenyl ethers were also prepared radiolabelled with 14C. The compounds were characterized by 1H NMR, melting points, mass spectrometry and UV. The structure of 2,2′,3,4,4′,5′-hexabromodiphenyl ether was unambigously determined by X-ray crystallography. Thereafter, the structure of the two pentabromodiphenyl ethers and remaining two hexabromodiphenyl ethers were assigned by comparison of their 1H NMR spectra with that of the 2,2′,3,4,4′,5′-hexabromodiphenyl ether.