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What are the second order reactions?
What are some good leaving groups? Bad ones and why?
Bromine adn iodine are good, as well as chlorine
Fluorine is a bad leaving group because it holds its electrons tightly
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What happens to the tetrahedron in SN2 reactions?
gets inverted because the nucleophile must approach the elctron 180 degrees behind the leaving group.
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What does the transition state of the second order reaction rates look like?
one bond is forming and the other is leaving
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What are SN1 and E1 only dependent on?
the substrate's concentration, not on the nucleophile
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What can you not do with --OH?
What can you do with alcohols?
What is acetate? Tosylate?
doesn't act as a leaving group; you can't kick it out. You can convert it to something that will leave
convert alcohols into tosillates
good nucleohile
good leaving group
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Since the energy of the transition state is significant in determining __, a __ will react more rapidly than __ (which is much more rapid than __).
If there's room __ behind the leaving group, what should happen?
- the rate of the reaction
- primary substrate
- secondary
- tertiary
- 180 degrees
- the reaction should go quickly
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If there's no space on the substrate, what can't you do? What will happen?
When will this occur?
- you can't substitute
- you either eliminate or there will be no reactin
in tertiary halides or if the nucleophile is too bulky; it will become E2 if there's no space
For E2, space is not a oncern
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What is protic? When don't we want this?
What are some protic examples?
__ should be able to __.
What do polar, protic solvents do?
- it can hydrogen bond
- in SN2 reactions
ethanol, methanol, H2O, etc.
polar, aprotic solvents; cage the metal cation
lower the energy of nucleophile
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We can think of the nucleophile as a __; so, we need a strong solvent to have what happen?
- salt
- get the nucleophile to break into its ions
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Tendency of a substance to behave as a nucleophile:
- strength parallels what? ex?
If you have too strong a base, what will happen?
What do we want for SN2?
- base strength; F is a weak base and even weaker nucleophile; Oh is both a strong base and a strong nucleophile
eliminiation
a good base that isn't strong enough to pluck
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Nucleophile strength roughly parallels ___.
Nucleophile strength increases __.
A base is always a stronger nucleophile than __.
Both NH2- and NH3 can act as nucleophiles; what is the only difference?
basicity
going down a group
its conjugate acid
the one with the negative is a stronger BL base
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Good leaving groups are __.
The C- LG (leaving group) bond is broken during __. What is crucial?
What is a group of excellent LGs?
The better the leaving group, what?
- weak bases
- RDS
- quality of leaving groups
- sulfonates
- the faster the rate occurs
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__ are easily prepared from alcohols.
__ can be good leaving groups. They can be easy to spot.
What is the only requirement?
- sulfonates
- neutral molecules
- has to be on a saturated center
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In a bimolecular elimination (E2), what does the nucleophile act as?
If the substrate is too congested, what doesn't happen? Why not?
- a bronsted base
- SN2; has more steric issues
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Which reactions compete?
- What does it depend on?
- What are good bases?
Good nucleophiles lead to __.
Bases prefer to __.
- Sn2 vs. E2
- Sn1 vs. E1
- the nature of the nucleophile
- alkoxides
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Sn2 competes with E2
- What are the guidelines for determining?
- - size of the base
- ---> bulky= E2
- - nature of the substrate
- ---> strong nucleophile, weak base= Sn2
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A strong nucleophile with primary carbons go through __.
What are Sn2 conditions?
- Sn2
- polar aprotic; low temp; good nucleophile
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What is a Beta carbon? What does it apply to?
What does coplanar mean?
- the carbon that is adjacent to the carbon carrying the leaving group; it produces an anti configuration
- SUBSTRATE MUST BE ANTI TO ONE ANOTHER
same plane
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In a cyclohexane, the leaving group must be __.
What is Zaitsev's rule?
axial
in an elimination reaction, the more highly substituted alkene (usually) predominates
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What is hyperconjugation?
The more overlap that occurs, what?
a pi bond associates with adjacent C-H antibonding bond
the lower the energy becomes
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