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what are free radicals?
very reactive intermediates
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Bond dissociation energy?
how much energy is required to break a bond
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Bond dissociation will tell us what?
whether it is exothermic versus endothermic
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Types of reactions
- addition
- elimination
- substitution
- rearrangement
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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
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Elimination Reaction
- what it does
- always forms?
- eliminate what?
- eliminates elements
- always form alkenes
- something from saturated/ neutral molecule to form pi bond
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Subsiitution Reaction
- competes?
- types?
- competes with elimination reaction
- substitutes an atom with another
- - polar vs nonpolar
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Polar Substitution reactions
- nucleophile and electrophile
- very polar solvent needed
- polar conditions
- has anions and cations as intermediates
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Nonpolar substitution reactions
- nonpolar process
- intermediates not charged
- neutral
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__ need light/ energy.
Sometimes, over an arrow, what do you see?
- photochemical reactions
- you see conditions
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All reactions need what?
energy
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Rearrangement reactions
- no adding, subtracting, or substituting
- rearrange electrons or atoms in a reaction
- needs catalyst
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Thermodynamics
study of energy changes
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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
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Rate equation
- describes kinetics of reaction
- if dependent on one reagent= first order
- two= 2nd order
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Bond breaking: nonpolar
- homolytic
- sigma bonds break
- one electron goes with each atom (fishhook demonstrates this)
- results in free radicals
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Bond breaking: polar
- heterolytic
- both electrons go to one species, usually the more electronegative
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If you can break bonds, __ all bond sforming must be __ as well.
SImilarly, all __ must form __ as well.
- homolytically x2
- heterolytic reactions
- heterolytic products
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bond forming
- homogenic: A⋅ + ⋅B --> A:B
- heterogenic: A+ + :B- --> A:B
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Nonpolar reactions involve __.
free radicals
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How can we quickstart a reaction?
introduce a radical, allowing the A:B to break
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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
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When doing chlorination, how much Cl2 do we want to break?
not all of them; just a little bit
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Forming a new radical creates a __
new scavenger
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Radicals are used as __.
beginning of the next step
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Eventually, you'll run out of energy. What happens?
free radicals find each other--> termination
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When does termination occur?
if you don't propagate another radical
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Explain bond dissociation energy?
- to break bonds, you put energy in (+)
- to form bonds, you get it back (-)
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