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Environmental Organic Chemistry Assessing the environmental behavior of organic chemicals Understanding of how molecular interactions and macroscopic transport.

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Presentation on theme: "Environmental Organic Chemistry Assessing the environmental behavior of organic chemicals Understanding of how molecular interactions and macroscopic transport."— Presentation transcript:

1 Environmental Organic Chemistry Assessing the environmental behavior of organic chemicals Understanding of how molecular interactions and macroscopic transport phenomena determine the distribution in space and time of organic chemicals released into natural and engineered environments Chemical structure and physical properties and reactivities Quantification of phase transfer, transformation and transport processes Mathematical models based on combining all relevant elements to assess behavior of organic chemicals 1

2 R.P. Schwarzenbach, Eawag/ETH, Switzerland 2 Textbook P.M. Gschwend, MIT, USA D.M. Imboden, ETH, Switzerland

3 DDT (dichlorodiphenyltrichloroethane) 3 Synthesized first in 1874 organochlorine insecticide great success in the second half of World War II to control malaria and typhus The Swiss chemist Paul Hermann Müller was awarded the Nobel Prize in Physiology or Medicine in 1948 "for his discovery of the high efficiency of DDT as a contact poison against several arthropods. After the war, DDT was made available for use as an agricultural insecticide and produced massively (40,000 tons per year)

4 DDT (dichlorodiphenyltrichloroethane) 4 In 1962, Silent Spring by American biologist Rachel Carson DDT and other pesticides may cause cancer and that their agricultural use was a threat to wildlife, particularly birds questioned the logic of releasing large amounts of chemicals into the environment without fully understanding their effects on ecology or human health the birth of the environmental movement Ban of DDT in the US in 1972 Ban of DDT for agricultural use worldwide under the Stockholm Convention

5 Production/Usage and Environmental Impacts 5

6 Issues of anthropogenic organic chemicals in the environment 6 Acute contamination (chemical accidents, spills, waste dump sites etc) 2007 South Korea oil spill

7 Issues of anthropogenic organic chemicals in the environment 7 Chronic contamination (everyday use in industry, household etc) Petroleum chemicals Solvents Polymers Pesticides/insecticides Pharmaceuticals Nanomaterials …. >300 million tons

8 Issues of anthropogenic organic chemicals in the environment 8 REACH, European Union Regulation of 18 December 2006 Registration, Evaluation, Authorisation and Restriction of Chemical addresses the production and use of chemical substances, and their potential impacts on both human health and the environment Requires all companies manufacturing or importing chemical substances into the European Union in quantities of one ton or more per year to register these substances with a new European Chemicals Agency the strictest law to date regulating chemical substances and will affect industries throughout the world

9 The needs and tasks of environmental organic chemistry 9 Impacts of organic chemicals (existing or new) to humans and ecosystems The processes that govern the transport/transfer and transformations of anthropogenic chemicals in the environment Identity unchanged processes: transport/mixing and phase transfer Identity changed processes: chemical, photochemical and biological transformation processes The effects of such chemicals on organisms (including humans), organism communities, and whole ecosystems

10 10 From Schwarzenbach et al., Science 2006

11 11 Environmental processes in a lake

12 12 General scheme for evaluation of the environmental behavior of anthropogenic organic compounds

13 13 Structure of the book and the scope of the lecture Part I. Ch.2. Introduction to environmental organic chemicals Part II. Phase transfer (partitioning) Ch3. theory of partitioning processes Ch4. vapor pressure Ch5. water solubility Ch6. air-liquid partitioning Ch7. organic liquid-water partitioning Ch8. organic acids and bases Ch9. partitioning to organic matters Ch10. partitioning to living media Ch11. partitioning to inorganic surfaces Part III. Transformation process Ch12. thermodynamics and kineitc concepts Ch13. chemical transformation-hydrolysis Ch14. chemical transformation-redox reactions Ch15. photochemical transformation-direct Ch16. photochemical transformation-indirect Ch17. biological transformaiton Part IV. Transport and mixing Ch18. Transport by random motion Ch19. Transport through boundaries Ch20. Air-water exchange Ch21. box models Ch22. models in space and time Part V. Environmental systems and case studies Ch23. Ponds, lakes and oceans Ch24. Rivers Ch25. groundwater

14 Schedule DatesubjectCh. Sep 3 Sep 5 Introduction to environmental organic chemistry-1,2 Ch.1 Ch.2 Sep 10 Sep 12 No class (faculty meeting) Introduction to environmental organic chemistry-3 Ch.2 Sep 17 Sep 19 Thermodynamics and kinetics of transformation reactions-1,2 Ch.12 Sep 24 Sep 26 No class (military service) Thermodynamics and kinetics of transformation reactions-3 Ch.13 Oct 01 Oct 03 No class Oct 08 Oct 10 Hydrolysis and other nucleophilic substitution-1 Undergraduate entrance exam (make up) Ch.13 Oct 15 Oct 17 Hydrolysis and other nucleophilic substitution-2,3 IERC symposium (make up) Ch.13 DatesubjectChapter Oct 22 Oct 24 Middle exam Redox reactions-1 Ch 14 Oct 29 Oct 31 Redox reactions-2 Redox reactions-3 Ch.14 Nov 5 Nov 7 Direct photolysis-1 Direct photolysis-2 Ch.15 Nov 12 Nov 14 Direct photolysis-3 Make-up Ch.15 Ch.16 Nov 19 Nov 21 Indirect photolysis-1 Indirect photolysis-2 Ch.16 Nov 26 Nov 28 Indirect photolysis-3 Biological transformation-1 Ch.16 Dec 3 Dec 5 Biological transformation-2 Biological transformation-3 Ch.16 Dec 10 Dec 12 Summary Final exam 1)Mon. Wed. 9.00 – 10:20, SESE building 209/210 2)Three classes for each chapter 3)Presentation for answering questions at the end of each chapter 4)middle and final exams 5)Notice by email or 14

15 Evaluation ItemsPointsnote Attendance-1 for each missing class Middle exam30 Final exam30 Homework (presentation for question) 206 homeworks Quiz202 or 3 quizs Total100 Contact/help Yunho Lee, SESE building 308, available time: Monday 10.30 – 12 am 15

16 Ch2. Introduction to environmental organic chemicals 16 Goal: refresh our memories with terminologies and basic chemical concepts of organic chemistry Ch-2.2. The makeup of organic compounds Organic compounds? Major elements, heteroatoms Elemental composition, molecular formula, and molar mass Electron shells of elements present in organic compounds Covalent bonding Bond energies (enthalpies) and bond lengths The concept of electronegativity Oxidation state of the atoms in organic molecules Spatial arrangement of the atoms in organic molecules (VSEPR) Steroisomerism Delocalized electrons, resonance and aromaticity

17 17

18 18

19 19

20 20 Bond angles

21 21 Isomers: compounds with the same molecular formula but different structural formulas Structural isomers: the atoms and functional groups are joined together in different ways Stereoisomers: the bond structure is the same, but the geometrical positioning of atoms and functional groups in space differs Enantiomers: different isomers are non-superimposable mirror-images of each other Geometric isomers: restricted rotation within the molecule (cis-E and trans-Z) Conformational isomers: free rotations around sigma bonds (usually not separable)

22 22 Ch-2.3. Classification, nomenclature, and examples of environmental organic chemicals Classification by physical/chemical properties: VOCs, hydrophobic compounds, surfactants, solvents Classification by source or use: solvents, plasticizers, pesticides, dyes and pigments, mineral-oil products Classification by chemical structure-functional groups: hydrocarbons, organohalogens, oxygen-, nitrogen-, and sulfur-containing compounds Systematic (IUPAC) names vs trivial names: lindane

23 23 Hydrocarbons Fossil fuels and synthetic processing of fossil fuels Liquid petroleum products 3 billion metric tons annually Typically hydrophobic Aliphatic, alicyclic, and olefinic hydrocarbons

24 24 Hydrocarbons BTEX: gasoline constituents, solvents, common groundwater pollutants PAHs: - combustion of fossil fuels, forest fires, direct input of mineral oils, use of creosotes as wood preservatives - benzo(a)pyrene, potent carcinogen - bioaccumulation Aromatic hydrocarbons

25 25 Organohalogens Largely anthropogenic source F and Cl form strong bonds with carbon, enhance of inertness (persistence) Halogens in organics enhance hydrophobicity, thus increase the partitioning to organic phases including organisms Stratosphere ozone depletion Global warming potential Need to develop alternatives Top groundwater pollutants Persistent, mobile Reductive dehalogenation

26 Organohalogens To date, > 1 million metric tons produced Waxes, printing inks, paints, lacquers, capacitor dielectric fluids, transformer coolants, hydraulic fluids, heat-transfer fluids, lubricants, plasticizers, fire retardants Some of them are banned or restricted in many countries Polychlorinated hydrocarbons

27 Organohalogens X = Cl, Br, I Halogenated compounds from chlorination of water or bleaching processes in the pulp and paper industry

28 Oxygen-containing functional groups Oxygen forms polar bonds -OH: both as H-donor and H- acceptor -ROR: H-acceptor -ROH, dissociation -15-20 million metric tons per year -MTBE: representative groundwater pollutant -Dioxins, PCDDs and PCDFs: produced from incineration -PBDEs: emerging contaminants, flame retardants

29 Oxygen-containing functional groups Aldehydes and ketones as reactive intermediates H-acceptor, solvents Carboxyl acids, anionic forms Both H-acceptor and H-donors Industrial production and environmental transformation products of organics e.g. atmospheric oxidation of haloethanes and haloethenes Carboxylic acid esters :phthalates as plasticizers Preventol B2 as roof protection materials, slow release of mecoprop

30 Nitrogen-containing functional groups

31 Amino groups: natural (amino acids, amino sugars) and anthropogenic (anilines etc) Cationic ammonium species (both H-acceptors and H-donors), surfactant Aromatic amines as  -electron donor, azo dyes Nitro groups: explosives, agrochemicals, dyes, atmospheric formation by nitration Strong electron-withdrawing character (acidity, oxidant) and delocalize  -electron (light absorption), reduction to nitroso, hydroxylamine, and amines

32 Sulfur-containing functional groups

33 Sulfur valence-shell expansion different from oxygen Less electronegative, more nucleophilic than oxygen Special double bond between S and O (d-orbital) Low-molecular weight mecarptans (reduced sulfur) as natural and anthropogenic source (herbicides, lower toxicity or target toxicity) Oxidized sulfur (sulfonic acid) LAS as major surfactants, anionic azo dye, whitening agents, detoxicification strategies Sulfonic acid derivatives, sulfon- amides

34 Phosphorus-containing functional groups P vs N P typically +III or V oxidation state Three single bonds and one double bonds Special double bonds Plasticizer, flame retardants, pesticides, chelating agent

35 More complex structures (e.g. bioactive compounds) Pesticides Pharmaceuticals

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