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Organic Reactions

Organic Reactions. Kinds of Reactions Mechanisms (polar, non-polar) Bond Dissociation Energy Reaction Profiles. Types of Reactions. Addition Reactions Elimination Reactions. Types of Reactions. Substitution: Polar Non-polar. Rearrangement. Definitions.

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Organic Reactions

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  1. Organic Reactions Kinds of Reactions Mechanisms (polar, non-polar) Bond Dissociation Energy Reaction Profiles

  2. Types of Reactions • Addition Reactions • Elimination Reactions

  3. Types of Reactions • Substitution: • Polar • Non-polar

  4. Rearrangement

  5. Definitions • Mechanism: Complete step-by-step of exactly which bonds break and which bonds form and in what order. • Thermodynamics: The study of the energy changes that occur in chemical transformations. This allows for comparison of stability of reactants and products. • Kinetics: The study of reaction rates, determining which products are formed most rapidly. One can predict how the rate will change with changing conditions.

  6. Reaction Profile (Exothermic)

  7. 2nd Order Reaction

  8. 1st Order Reaction

  9. Bond Breaking:Non-polar and Polar

  10. Bond Forming:Non-polar and Polar

  11. Non-polar Reaction Involves Free Radicals

  12. Free Radicals are Neutral, but Electron-Deficient

  13. Free Radical Chlorination

  14. Experimental Evidence Helps to Determine Mechanism • Chlorination does not occur at room temperature in the dark. • The most effective wavelength of light is blue that is strongly absorbed by Cl2 gas. • The light-initiated reaction has a high quantum yield (many molecules of product are formed from each photon of light).

  15. Free Radical Species are Constantly Generated Throughout the ReactionPropagation

  16. Termination: Reaction of any 2 Radicals

  17. Enthalpy of Reaction (DHo) Measures Difference in Strength of Bonds Broken and Bonds FormedBond Dissociation Energy

  18. DHo = Sbonds broken-Sbonds formed

  19. DHrxn = -105 kJ/mol

  20. Why Not This Mechanism?

  21. Chlorination of Propane

  22. H’s are not abstracted at the same rate.

  23. Chlorinationof Methylpropane

  24. Tertiary H’s removed 5.5 times more readily than primary H’s in chlorination reactions

  25. 3o Radicals are Easiest to Form

  26. Stability of Free Radicals

  27. Bromination is Very Selective

  28. RDS in Bromination is highly endothermic

  29. Consider the free radical monochlorination of 2,2,5-trimethylhexane. Draw all of the unique products (ignore stereoisomers; use zig-zag structures please) and predict the ratio or percent composition of the products.The relative reactivity of H abstraction in a chlorination reaction: 1o: 2o: 3o = 1: 4.5: 5.5

  30. Chlorofluorocarbons and the Depletion of Ozone

  31. Polar Reactions:Nucleophiles & Electrophiles

  32. Nucleophiles are BasesElectrophiles are Acids

  33. Addition of HBr to Ethylene

  34. Reactions Often Go Through Intermediates

  35. Transition State

  36. Addition Reaction is a Two-Step Mechanism

  37. How Many Mechanistic Steps?How Many Intermediates?How Many Transition States?Which Step is Rate-Determining?

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