X-ray structural studies on organobromine and organochlorine compounds

Abstract

The structures of nine organic compounds containing bromine or chlorine were studied by single crystal X-ray diffraction. The compounds belong to two different classes of halogenated organics. Three of the compounds were polybrominated polycyclic ethers formed through transannular reactions during the treatment of two isomers of cyclododeca-1,5,9-triene with N-bromosuccinimide in methanol. These compounds were endo,endo-5,9-dibromo-cis-transoidcis-13-oxa-tricyclo[8.2.l.02.6]tridecane (I), endo,endo,exo-2,6,10-tribromo-exo-5-methoxy-13-oxa-trans-bicyclo[7.3.1]tridecane (II) and (E)-exo,endo-2,5,10- tribromo-exo-6-methoxy-13-oxa-cis-bicyclo[7.3.1]tridec-4-ene (III). The remaining six compounds were polychlorinatied aromatics used as model compounds in environmental analyses: 1,2,3,4-tetrachlorodibenzo-p-dioxin (IV), pentachloromethoxy benzene (V), 2,2',3,4',5'-pentachloro-4-methoxybiphenyl (VI), 2,2',4,4',5',6-hexachloro-3-methoxybiphenyl (VII), bis(2,4-dichlorophenyl) ether (VIII) and 2,2',3,4,4',5'-hexachlorodiphenyl ether (IX). All structures were solved by Direct Methods, but the procedure used for the three brominated polycyclic ethers differed from the normal one. These compounds were taken for structure analysis directly from the synthesis, with no other information available about their chemical composition except that provided by the synthesis. A qualitative procedure for estimating the chemical composition from experimental crystallographic data and information about the synthesis is described and is applied as an expedient to structure solution for the three compositionally indeterminate polycyclic bromo compounds.