additions - TOPIC 8. ADDITIONS TO ALKENES AND ALKYNES...

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CHEM 2311 B Topic 8 slide 1 TOPIC 8. ADDITIONS TO ALKENES AND ALKYNES (Chapter 8 and parts of chapters 7, 10 and 11) CHEM 2311 B Topic 8 slide 2 OBJECTIVES 1. Describe mechanisms for addition reactions of alkenes and alkynes 2. Predict the structure of the product(s) of addition reactions 3. Understand the mechanisms which explain the regiochemical and stereochemical outcome of addition reactions 4. Use combination of substitution, elimination and addition chemistry to propose synthetic routes to useful value-added compounds
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Flashcards CC OH Br Br 2 anti addition Substrate Reagent Product Stereospecificity Regiochemistry H 2 O Front Back 1 Substrate and Reagent Product (stereospecificity and regiospecificity) 2 Reagent and Product Substrate 3. Substrate and Product Reagent Markovnikov CHEM 2311 B Topic 8 slide 4 Outline: Additions to Alkenes and Alkynes 1. Hydrogenation – cis addition 2. Dissolving Metal Reductions- trans addition 3. Addition of H-X : Markovnikov’s rule – carbocation stability
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CHEM 2311 B Topic 8 slide 5 4. Addition of H 2 O; H + catalyzed, rearrangements common 5. Oxymercuration-Demercuration – avoids rearrangements, follows Markovnikov’s rule 6. Hydroboration – anti- Markovnikov’s rule Outline: Additions to Alkenes and Alkynes cont’d CHEM 2311 B Topic 8 slide 6 7. Hydration of Alkynes – ketone formation 8. Addition of Br 2 and Cl 2 ; 1,2 Additions via anti- addition 9. Addition of X 2 /H 2 O: Halohydrin formation via anti- addition Outline: Additions to Alkenes and Alkynes cont’d
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CHEM 2311 B Topic 8 slide 7 10.Carbene Additions: Alkenes to cyclopropanes 11.Epoxide formation – alkenes to epoxides (oxiranes) 12.Oxidation of Alkenes and Alkynes – syn hydroxylation Outline: Additions to Alkenes and Alkynes cont’d CHEM 2311 B Topic 8 slide 8 13.Oxidative Cleavage of Alkenes 14.Oxidative Cleavage of Alkynes 15.Designing Synthesis – synthetic strategies Outline: Additions to Alkenes and Alkynes cont’d
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CHEM 2311 B Topic 8 slide 9 HYDROGENATION OF ALKENES AND ALKYNES Hydrogenation of Alkenes CH 3 3 H 2 Pd or Pt Prob: 7.40-42; 8.30e,g,i, 37,45 S:7.12-7.14 CHEM 2311 B Topic 8 slide 10 A Practical Application of Hydrogenation – Hydrogenated Oils and Fats H 2 C HC H 2 C O O (CH 2 ) 7 CH 2 CH 3 O O (CH 2 ) 7 (CH 2 ) 7 CH 3 O O (CH 2 ) 14 CH 3 H 2 C HC H 2 C O O (CH 2 ) 16 CH 3 O O (CH 2 ) 16 CH 3 O O (CH 2 ) 14 CH 3 H 2 /Pt Soybean Oil Mixture of saturated and various cis -unsaturated hydrocarbon chains. Low melting (-16 °C) because cis C=C impede crystallization. Margarine Mixture of saturated hydrocarbon chains (some C=C kept to adjust consistency). Saturated alkyl chains pack together (crystallize). http://www.fb.com/nefb/ag-ed/soybean.gif http://www.bassriverchairs.com/new_prodMargarine.html http://www.nicssa.co.uk/Contentpages/Fitness&Exercise/contentweightetc.htm
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CHEM 2311 B Topic 8 slide 11 Hydrogenation of Alkynes Complete Hydrogenation cis-Semihydrogenation CC H 2 Pt or Pd H 2 Pd/CaCO 3 N CHEM 2311 B Topic 8 slide 12 2Li, 2CH 3 OH NH 3 (solvent) Li Li Li Dissolving Metal Reduction
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CHEM 2311 B Topic 8 slide 13 PREVIEW OF REACTIVITY
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additions - TOPIC 8. ADDITIONS TO ALKENES AND ALKYNES...

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