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Relevant academic research and scientific papers

Toxaphene chemistry: Separation and characterisation of selected enantiomers of the Polychloropinene mixtures

The primary goal for the study presented here was the preparation and characterisation of enantiomeric pure chlorobornane standards (Toxaphene). In this context, we partially modeled the procedure for Polychloropinene production in the former USSR. The initial reaction was ionic addition of hydrogen chloride to (1S)-α-pinene resulting predominantly in (1S)-2-endo-chlorobornane. Further photochlorination gave mixtures of chlorinated terpenes with different average content of Cl per molecule. The resulting mixtures were separated on a silica-gel column and a number of known hepta to decachlorobornanes were identified in fractions with the help of NMR and GC (using electron capture and mass spectrometric detection) - but in very unusual ratios as compared to the technical Toxaphene mixture formerly produced by Hercules (USA). Also several previously unknown congeners were isolated or detected. Three of the isolated congeners were obtained in crystalline state and X-ray crystallography showed their enantiomeric purity.

Synthesis of two major toxaphene components and their photostabilities

The synthesis of 2-endo,3-exo,5-endo,6-exo,8,9,10-heptachlorobornane (B7-1001, Hp-Sed) and 2-endo,3-exo,5-endo,6-exo,8,9,9,10-octachlorobornane (B8-1412) is described. Both compounds are components of toxaphene, an insecticide that has been widely used in the past. B7-1001 is an important toxaphene congener, comprising up to 99% of total toxaphene concentrations found in fish and sediment samples from treated lakes. B8-1412 is also a significant component of toxaphene contamination in samples from biota. In synthesizing the compounds, 2-exo,3-endo,6-endo,8,9,10-hexachlorobornane (B6-913) was obtained by reduction of the well-known toxaphene component P 32 (B7-515, 2,2,5-endo,6-exo,8,9,10-heptachlorobornane), which was itself isolated from the chlorination products of (+)-camphene. Chlorination of B6-913 provided B7-1001 in 49.5% yield, and P 32 and four other heptachlorobornanes were also detected in the reaction mixture. Structures of two of the heptachlorobornanes were elucidated by MS and NMR as 2-exo,3-endo,6-endo,8,9,9,10-heptachlorobornane (B7-1461) and 2-exo,3,3,6-encto,8,9,10-heptachlorobornane (B7-1303). B8-1412 was isolated from the product mixture obtained by chlorination of 2-exo,3-endo,6-endo,8,9,9,10-heptachlorobornane. Photolysis experiments at λ = 254 nm revealed that B6-913 is photochemicaly the most stable compound of the seven toxaphene compounds studied, with a t1/2 of 213 h. B7-1001, having a t1/2 of 82 h, was the second most stable compound. B8-1412 was degraded more rapidly, with a t1/2 of 28.8 h, than B7-1001, but was still much more stable than P 50 (B9-1679, 2-endo,3-exo,5-endo,6-exo,8,8,9,10,10-nonachlorobornane), which had a t 1/2 of 9.4 h, despite its reputation as a very persistant compound. Under the same experimental conditions hexachlorobenzene (HLB) and octachlorodibenzodioxine (OCDD) were consumed very quickly with t1/2 = 0.0025 and 0.0015 h, respectively.