1. University of Texas at AustinMichigan Technological University 1 Module 2: Evaluating Environmental Partitioning and Fate: Approaches based on chemical structure - Chapter 5 David Allen Department of Chemical Engineering University of Texas at Austin

2. Michigan Technological University 2 Module 2: Evaluating Environmental Partitioning and Fate: Approaches based on chemical structure l Educational goals and topics covered in the module l Potential uses of the module in chemical engineering courses l Overview of property estimation methods l Software demonstration l Case studies

3. University of Texas at AustinMichigan Technological University 3 Module 2: Educational goals and topics covered in the module Students will: l become aware of the chemical and physical properties that govern a chemical’s environmental partitioning and fate l be able to estimate properties that govern environmental partitioning and fate based on chemical structure l be able to perform mass balances to estimate environmental partitioning and be able to design structures that have targeted properties l be aware of the limitations of structure-property estimation methods

4. University of Texas at AustinMichigan Technological University 4 Module 2: Educational goals and topics covered in the module (cont’d) Properties covered: l Properties used to estimate partitioning: boiling point, vapor pressure, octanol-water partition coefficient, bioconcentration factor, Henry’s law coefficient, soil sorption l Properties that govern environmental fate: atmospheric lifetimes, biodegradation rates l Typical values of properties l Environmental partitioning calculations

5. University of Texas at AustinMichigan Technological University 5 Module 2: Potential uses of the module in chemical engineering courses l Design course: Use as a preliminary screen of chemical products and raw materials l Materials course/thermodynamics course: Module on estimating properties l Mass and energy balances course: module on estimating mass partitioning in closed systems

6. University of Texas at AustinMichigan Technological University 6 Module 2: Chemical properties for environmental decision-making

7. University of Texas at AustinMichigan Technological University 7 l Empirical approach based on exp. Data »Specific to chemical classes »Termed structure-activity relationships (SARs) l Approaches in Ch 5 »Functional Groups (K OW, k OH, P Bio ) »Bond Types (H) »Molecular Connectivity (K OC ) »Linear Free Energy (k Hyd ) Module 2: Property estimation methods based on chemical structure

8. University of Texas at AustinMichigan Technological University 8 l Based on K OW, octanol-water partitioning »BCF - bioconcentration factor »LC50 - lethal dose 50% mortality »S - water solubility of organic compounds »K OC - organic carbon/water partitioning Module 2: Property estimation methods based on other properties

9. University of Texas at AustinMichigan Technological University 9 l K OW - octanol-water partitioning Describes partitioning of organic pollutants between the water phase and octanol Module 2: Functional groups log K ow = 0.229 +  n i f i +  n j c j n = number of functional groups of types i or j f i = contribution to log K ow of group i c j = correction factor for functional group j

10. University of Texas at AustinMichigan Technological University 10 Module 2: Functional groups 1,1-Dichloroethylene example the molecular structure, CH 2 = CCl 2 one =CH 2 group one =CH- or =C< group two –Cl (olefinic attachment) groups log K ow = 0.229 + 0.5184 + 0.3836 + 2(0.4923) = 2.11 (no correction groups) Experimental log K ow = 2.13

11. University of Texas at AustinMichigan Technological University 11 l H - Henry’s law constant Describes partitioning of organic pollutants between the water phase and air in the environment Module 2: Bond Types -log H =  n i h i +  n j c j n = number of bonds of types i or j h i = contribution to H of bond type i c j = functional group correction factor

12. University of Texas at AustinMichigan Technological University 12 Module 2: Bond Types 1-propanol example the molecular structure, H H H    H – C – C – C – O - H    H H H 7 C-H bonds, 2 C-C bonds, 1 C-O bond, and 1 O-H bond -log H = 7(-0.1197) + 2(0.1163) + 1.0855 + 3.2318 = 3.7112 w correction; - log H = 3.7112 - 0.20 = 3.5112 linear or branched alcohols Experimental -log H = 3.55

13. University of Texas at AustinMichigan Technological University 13 l K OC - Organic carbon-water partition coeff. Describes partitioning of organic pollutants between the water phase and natural organic matter in soils/sediments Module 2: Molecular connectivity log K oc = 0.53 1  + 0.62 +  n j P j 1  = 1 st order molecular connectivity index n j = number of groups of type j P j = correction factor for group j

14. University of Texas at AustinMichigan Technological University 14 Module 2: Molecular connectivity 1-hexanol example the molecular structure, CH 3 – CH 2 – CH 2 – CH 2 – CH 2 – CH 2 – O - H  (1) (2) (2) (2) (2) (2) (1) - atom connectivity (  i,  j ) (1,2) (2,2) (2,2) (2,2) (2,2) (2,1) - bond connectivity 1  =  (  I *  j ) -0.5 1  = (1/  2) + (1/  4) + (1/  4) + (1/  4) + (1/  4) + (1/  2) = 3.41 log K oc = 0.53 1  + 0.62 +  n j P j log K oc = 0.53 (3.41) + 0.62 + (-1.519) = 0.91 Experimental log K oc = 1.01 aliphatic alcohol

15. University of Texas at AustinMichigan Technological University 15 Chemical structure provides an incomplete description of molecular interactions leading to observable properties Correction Factors for intermolecular forces »Electronic interactions »Multiple hydrogen bonding »Substituent effects Module 2: Correction Factors

16. University of Texas at AustinMichigan Technological University 16 Module 2: Software EPIWIN collection of software programs - Properties covered: l Properties used to estimate partitioning: boiling point, vapor pressure, octanol-water partition coefficient, bioconcentration factor, Henry’s law coefficient, soil sorption l Properties that govern environmental fate: atmospheric lifetimes, biodegradation rates

17. University of Texas at AustinMichigan Technological University 17 Mackay et al., “Illustrated Handbook of Physical-Chemical Properties and Environmental Fate for Organic Chemicals”, Lewis Publishers, 1992 Water Compartment Only 1 kg Hexachlorobenzene (Hx) 10 5 m 3 volume of water 10 -3 kg organic carbon / m 3 water 0.1 kg fish / 100 m 3 water Module 2, Case study 1: Environmental partitioning case study Human Exposure : Fish Ingestion 0.5 kg of fish consumed Dose due to ingestion? Concentration in the Fish (mg/kg)?

18. University of Texas at AustinMichigan Technological University 18 Module 2, Case study 1: Mass balance equation for Hx 118-74-1

19. University of Texas at AustinMichigan Technological University 19 EPIWIN: Software demonstration 10 5 m 3 10 -3 kg OC /m 3 3,388 L/ kg OC 10 -1 kg F / 10 2 m 3 5,152 L/ kg F 10 -3 m 3 /L Concentration in Water Concentration in Fish Dose to Humans

20. University of Texas at AustinMichigan Technological University 20 Module 2, maleic anhydride 108-31-6 EPIWIN (estimates) vs ChemFate (data) No data because MA hydrolyzes in 1 minute in water

21. University of Texas at AustinMichigan Technological University 21 Module 2, Benzene 71-43-2 EPIWIN (estimates) vs ChemFate (data)

22. University of Texas at AustinMichigan Technological University 22 Module 2: Recap l Educational goals and topics covered in the module l Potential uses of the module in chemical engineering courses l Overview of property estimation methods l Software demonstration l Case studies