Endosulfan has been identified as a persistent organic pollutant (POP) due to its persistence, bioaccumulation, long-range transport, and adverse effects to human health and aquatic ecosystems. Phased-out in the United States will occur in 2016. Endosulfan consists of two diastereomers, a and �. a-Endosulfan exists as two asymmetrical, twist-chair enantiomers which interchange, while �-endosulfan has a symmetrical-chair conformation. �-Endosulfan has been shown to isomerize to a-endosulfan. Previously-proposed isomerization mechanism was re-examined using temperature-dependent Raman (TDR) spectroscopy. The bending frequencies in the fingerprint region were assigned to specific bonds. Changes in the signal intensity as a function of temperature were used to identify detailed ring movements, and thus conversion of � to a. These movements cannot occur simultaneously nor symmetrically, precluding conversion of a-endosulfan to �-endosulfan. Furthermore, this mechanism explains the overwhelming presence of a-endosulfan in air samples.

Discerning the flexibility and rigidity of �-endosulfan isomerization to a-endosulfan using temperature-dependent Raman (TDR) spectroscopy: Influences on environmental fate

248th National Meeting (2014)

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