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