U.S. flagAn official website of the United States government
                    Here's how you know **Official websites use .gov**
                            
                            A **.gov** website belongs to an official government organization in the United States.
 **Secure .gov websites use HTTPS**
                            
                            A **lock** (                            
                              A locked padlock                                                      
                            
                            ) or **https://** means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Menu Agricultural Research Service
						
                    U.S. DEPARTMENT OF AGRICULTURE
 Hydrology and Remote Sensing Laboratory: Beltsville, MD
 close



    Research

                    Research Projects
                                    Publications
                                    Collaborations
                                    News
                                    Software
                People

                    Staff Listing
                                    CareersSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home Northeast Area Beltsville, Maryland (BARC) Beltsville Agricultural Research Center Hydrology and Remote Sensing Laboratory Research Publications at this Location





- ARS National Programs
- Search for a scientific manuscript
- Search for a research project
- ARS Software
- Programs and Projects
- Collaborations
- Subjects of Investigation
- Publications
- People
- Research Sites
- Pesticide Volatilization
- Watershed Modeling
- Climate Change
- Soil Moisture
- Drought and ET
- HRSL Brochure

Title:   Author  item
                                            SCHMIDT, WALTER - US Department Of Agriculture (USDA)item
                                            Hapeman, Cathleenitem
                                            McConnell, Lauraitem
                                            MOOKHERJI, SWATI - US Department Of Agriculture (USDA)item
                                            NGUYEN, JULIE - US Department Of Agriculture (USDA)item
                                            QIN, JIANWEI - US Department Of Agriculture (USDA)item
                                            LEE, HOYOUNG - US Department Of Agriculture (USDA)item
                                            CHAO, KEVIN - US Department Of Agriculture (USDA)item
                                            KIM, MOON - US Department Of Agriculture (USDA)
  Submitted to: Journal of Agricultural and Food Chemistry
                                    Publication Type: Peer Reviewed Journal
                                    Publication Acceptance Date: 2/3/2014
                                    Publication  Date: 2/3/2014
                                    Publication URL: http://handle.nal.usda.gov/10113/59807Citation: Schmidt, W., Hapeman, C.J., McConnell, L.L., Mookherji, S., Nguyen, J.K., Qin, J., Lee, H., Chao, K., Kim, M. 2014. Temperature dependent Raman Spectroscopic evidence of and molecular mechanism for thermal transfer between Beta-Endosulfan and Alpha-Endosulfan. Journal of Agricultural and Food Chemistry. 62:2023-2030.Interpretive Summary: Endosulfan is a broad-spectrum, organochlorine insecticide used on numerous crops since the 1950's. It is a persistent organic pollutant (POP) due to its stability, bioaccumulation, long-range transport in the atmosphere, and adverse effects to aquatic ecosystems and to human health. Endosulfan is scheduled to be phased out in 2016 in the United States, but due to its persistence in soil and its long-range transport, it will remain a global issue long after its use has ceased. Endosulfan is a mixture of two chemicals, alpha-endosulfan and beta-endosulfan, and they move in the environmental differently.  In addition, earlier research has shown that beta-endosulfan can change into alpha-endosulfan.  This was an important finding since beta-endosulfan is thought to degrade faster than alpha-endosulfan.  Simulations experiments and chemical calculations were carried out to explain this conversion.  In this study, a newly-developed technique called temperature-dependent Raman (TDR) spectroscopy was used to document the actual changes and movements of the bonds involved when beta-endosulfan changes to alpha-endosulfan. These experiments also provide the first tangible evidence for why alpha-endosulfan cannot convert to beta-endosulfan.  These results are important because alpha-endosulfan volatilizes more easily than beta-endosulfan and it is easily transported to remote areas, such as the Arctic Circle.
                                Technical Abstract: Endosulfan (6,7,8, 9,10,10-hexachloro-1,5,5a,6,9,9a-hexahydro-6,9-methano-2,4,3-benzodioxathiepine-3-oxide) is a broad-spectrum, organochlorine insecticide used on numerous crops since the 1950's. It 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 and will be phased-out in the United States in 2016. Endosulfan consists of two diastereomers, alpha and beta, and while the alpha-isomer exists as two asymmetrical, twist-chair enantiomers which interchange, the beta-isomer is a symmetrical-chair conformation. Furthermore, the beta-isomer has been observed to isomerize to the alpha-isomer. Here we document the previously proposed isomerization mechanism using temperature-dependent Raman (TDR) spectroscopy.  The bending frequencies in the fingerprint region were assigned to specific bonds. Changes in the signal intensity at certain frequencies as a function of temperature were used to identify detailed ring movements, and thus the isomerization mechanism.  These movements cannot occur simultaneously nor symmetrically, and thereby preclude conversion of the alpha-isomer to the beta-isomer. These results will be of interest to other scientists and regulatory agencies.


Return to top


Connect with ARS Sign up


ARS Home
                            USDA.gov
                            Plain Writing
                            Policies & Links
                            Civil Rights Statements
                            FOIA
                            Accessibility Statement
                            Privacy Policy
                            Non-Discrimination Statement
                            Quality of Information
                            USA.gov
                            WhiteHouse.gov