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ARS Home » Northeast Area » Beltsville, Maryland (BARC) » Beltsville Agricultural Research Center » Hydrology and Remote Sensing Laboratory » Research » Publications at this Location » Publication #309938
Title: Discerning the flexibility and rigidity of beta-endosulfan isomerization to alpha-endosulfan using temperature-dependent Raman (TDR) spectroscopy: Influences on environmental fate

Author
item Schmidt, Walter
item Hapeman, Cathleen
item Rice, Clifford
item McConnell, Laura

Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 7/1/2014
Publication Date: 8/10/2014
Citation: Schmidt, W.F., Hapeman, C.J., Rice, C., Mcconnell, L.L. 2014. Discerning the flexibility and rigidity of beta-endosulfan isomerization to alpha-endosulfan using temperature-dependent Raman (TDR) spectroscopy: Influences on environmental fate [abstract]. American Chemical Society. AGRO 479.

Interpretive Summary:

Technical Abstract: 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, alpha and beta. Alpha-Endosulfan exists as two asymmetrical, twist-chair enantiomers which interchange, while beta-endosulfan has a symmetrical-chair conformation. Beta-Endosulfan has been shown to isomerize to alpha-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 beta to alpha. These movements cannot occur simultaneously nor symmetrically, precluding conversion of alpha-endosulfan to beta-endosulfan. Furthermore, this mechanism explains the overwhelming presence of alpha-endosulfan in air samples.