Ch 4 Pt 1 Notes

  1. what are free radicals?
    very reactive intermediates
  2. Bond dissociation energy?
    how much energy is required to break a bond
  3. Bond dissociation will tell us what?
    whether it is exothermic versus endothermic
  4. Types of reactions
    • addition
    • elimination
    • substitution
    • rearrangement
  5. Addition reactions
    - complexity? 
    - mechanism?
    - type of reaction?
    - entropy?
    • simple
    • has mechanism
    • polar reactions (2 reactants added up)
    • entropy goes down because two species become one
  6. Elimination Reaction
    - what it does
    - always forms?
    - eliminate what?
    • eliminates elements
    • always form alkenes
    • something from saturated/ neutral molecule to form pi bond
  7. Subsiitution Reaction
    - competes?
    - types?
    • competes with elimination reaction
    • substitutes an atom with another
    • - polar vs nonpolar
  8. Polar Substitution reactions
    • nucleophile and electrophile
    • very polar solvent needed
    • polar conditions
    • has anions and cations as intermediates
  9. Nonpolar substitution reactions
    • nonpolar process
    • intermediates not charged
    • neutral
  10. __ need light/ energy. 
    Sometimes, over an arrow, what do you see?
    • photochemical reactions 
    • you see conditions
  11. All reactions need what?
    energy
  12. Rearrangement reactions
    • no adding, subtracting, or substituting
    • rearrange electrons or atoms in a reaction
    • needs catalyst
  13. Thermodynamics
    study of energy changes
  14. What do we want to do?
    What controls the reaction? 
    What is the deal with the above answer?
    • drive equilibrium products to completion
    • Ea
    • if you can't get past it, reaction doesn't occur
  15. Rate equation
    • describes kinetics of reaction
    • if dependent on one reagent= first order
    • two= 2nd order
  16. Bond breaking: nonpolar
    • homolytic
    • sigma bonds break
    • one electron goes with each atom (fishhook demonstrates this)
    • results in free radicals
  17. Bond breaking: polar
    • heterolytic
    • both electrons go to one species, usually the more electronegative
  18. If you can break bonds, __ all bond sforming must be __ as well.
    SImilarly, all __ must form __ as well.
    • homolytically x2
    • heterolytic reactions 
    • heterolytic products
  19. bond forming
    • homogenic: A⋅ + ⋅B --> A:B
    • heterogenic: A+ + :B- --> A:B
  20. Nonpolar reactions involve __.
    free radicals
  21. How can we quickstart a reaction?
    introduce a radical, allowing the A:B to break
  22. Explain chlorination
    • doesn't occur in dark room
    • most effect wavelength= blue light
    • high quantum ueild: making molecuels of products with single photon of light
  23. When doing chlorination, how much Cl2 do we want to break?
    not all of them; just a little bit
  24. Forming a new radical creates a __
    new scavenger
  25. Radicals are used as __.
    beginning of the next step
  26. Eventually, you'll run out of energy. What happens?
    free radicals find each other--> termination
  27. When does termination occur?
    if you don't propagate another radical
  28. Explain bond dissociation energy?
    • to break bonds, you put energy in (+)
    • to form bonds, you get it back (-)
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DesLee26
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Ch 4 Pt 1 Notes
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