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
 close



Research
                Research Home
                            National Programs
                            Research Projects
                            Scientific Manuscripts
                            International Engagement
                            Scientific Software/Models
                            Databases and Datasets
                            Office of Scientific Quality Review
            Media
                News & Features
                            Multimedia
                            Briefing Room
                            Down on the Farm
                            Press Room
                            Science in Your Shopping Cart
                            Scientific Discoveries
                            Tellus
                            Under the Microscope
            About ARS
                About ARS Home
                            Staff Directory
                            Labs and Research Centers (Map)
                            Headquarter Offices
                            Organizational Chart
                            Employee Services (REE Employees Only)
                            Office of Outreach, Diversity, and Equal Opportunity
            Work With Us
                Work With Us Home
                            ARS Vacancies at USAJOBS
                            Careers at ARS Information
                            Scientific Collaborations
                            Extramural Agreements
                            1890 Faculty Research Sabbatical ProgramSearch small
                    Search
            
            ARS Home
                                About ARS
                                Contact Us




ARS Home 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

Title:   Author  item
                                            Hapeman, Cathleenitem
                                            Schmidt, Walteritem
                                            BILBOULIAN, SUSANNA - UNIV MDitem
                                            Rice, Clifforditem
                                            FETTINGER, JAMES - UNIV MDitem
                                            McConnell, Laura
  Submitted to: Society of Environmental Toxicology and Chemistry (SETAC)
                                    Publication Type: Abstract Only
                                    Publication Acceptance Date: 11/11/2001
                                    Publication  Date: N/A
                                    Citation: N/AInterpretive Summary:
                                Technical Abstract: Formulated endosulfan exists as a 7:3 alpha to beta isomeric mixture but the observed ratio in the environment varies. The alpha form is the overwhelmingly-predominant isomer in air samples, beta  is favored in rain and alpha is generally greater in snow.  The asymmetry of alpha-endosulfan and the corresponding symmetry of beta-endosulfan were recently  established.  Data have also been presented demonstrating that the beta isomer converts to the alpha isomer, but that the reverse process does not occur under the same conditions. This study explains the observed phenomenon using physical properties, spectral evidence and computational chemistry.  Differential scanning calorimetry data indicated several phase changes in isomerically pure and mixtures of endosulfan.  A eutectic concentration of approximately 63:37 alpha to beta was observed.  NMR data of mixtures confirmed that both isomers influence the conformer  populations in solution.  Computational chemistry demonstrated that the S=O configuration is responsible for initiating the conversion of beta-endosulfan to alpha.  Further calculations indicated that in mixtures, the asymmetrical conformation of the sulfite in alpha can induce asymmetry in beta-endosulfan and allow the conversion to occur.  These same data preclude the probability of the reverse process and offer an explanation for isomeric compartmentalization.


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