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41 Cards in this Set

  • Front
  • Back
What determines the rate in Sn1 rxns?
Which rxns forms a carbocation?
Sn1, E1
What is the effect of substrates on Sn1 and Sn2 rxns?
Sn1: Fastest with primary substrates, slowest with tertiary.

Sn2: Opposite
What are the effects of nucleophiles on Sn1 and Sn2?
Sn1: no effects

Sn2: Fastest with strong nucelophiles
Describe weak, moderate, and strong nuc.
Weak: no charge, but have LP's

Moderate: neg charge, but stable, resonance

Strong: Neg charge, unstable
Describe excellent, good, and poor LG
Excellent: no charge

Good: (-) charge, but stable

Poor: (-) charged, unstable
What's the difference between nucleophiles and bases?
Nuc: attack Carbon atoms and sticks to molecule.

Bases: attack H and carries it off.
What are the effects of LG on Sn1 and Sn2?
Sn1: Fastest with Exc LG, more sensitive than Sn2

Sn2: also fastest with Exc LG
What's the difference between nucleophiles and electrophiles?
Nuc: e- rich, use e-s to attack sth

Elc: e- poor, full/partial (+) charge
What is hyperconjugation?
and what does it explain?
Overlap of alkyl goup over C-cation's empty p orbitals.
explains why alkyl groups are e- donating.
How can C-cations rearrange themselves to be more stablized?
Methyl and hydride shifts
How to start with see an alkyl with no functional groups?
Br2 and hv (see p 44 in notes)
What are the 4 factors for Sn1 and Sn2?
Prim, Secondary, Tertiary substrates

str/mod/weak nuc

exc/good/poor LG

The more/less basic the nuc, the more favorable for E1.
What does basicity and nucleophility depend on?
Basicity: stability of charge (thermodynamics)

Nucleophilicity: rate of attack (kinetics)
In an alkene, which is more stable: cis/trans, more/less substituted alkene?
trans, more substituted
Protonation and loss of H20 characterizes which rxn?
What are the effects of primary, secondary, and tertiary substrates on E2 and Sn2?

What would favor elimination over substitution?
Only E2 happens in tertiary.
Both in secondary
Only Sn2 in primary.

Bulky nuc/bases favor elim. over sub!
Which nuc do you use to get Zaitsev and Hoffman products in a an elimination?
Zaitsev: EtO-
Hoffman: tBuO-
What rxns will a strong reagent have?

Strong: Sn2 or E2
Weak: Sn1 or E1
What are some reagents that are only nuc?
Only bases?
Nuc: Br-, Cl-, I-, HS-, RS-, H2S, RSH

Bases: H-, tBu0-

Both: H20, ROH, RO-, OH-
Bromonium rxn is anti or syn? Why?
Can only be anti b/c the Br- must attack on the other side of the ring (not the side of bromonium biridge) to break open the bridge
What's the difference b/w stereochemistry and regiochemistry?
Stereochemistry: configuration of stereocenters (R v S) and double bonds (E v Z)

Regiochemistry: where the rxn takes place
What are the terminology associated witih stereochemistry and regiochemistry?
Stereochemistry: syn, anti
Regiochemistry: (addition) Markovnikov, anti-markovnikov; (elimination) Zaitsev, Hoffman
When does syn/anti addition matter?

When does anti/Markovnikov matter?
S/A: When creating 2 stereocenters

A/M: When adding 2 Different groups
What type of solvent favors Sn2? Why?
Polar aprotic solvents

Aren't good at forming solvent shells, so won't get in the way of nuc-
What's the difference b/w sub and elim?
Sub: another atom replaces halide ion

Elim: halide ion leaves with another atom or ion
What are the trends with nucleophilicity in the periodic table?
It decreases from left to right b/c ENeg increases from left to right

It also inc down the table b/c of the inc in size and polarizability
Define steric hindrance
Bulky groups interfere with a rxn by virtue of their size
What's a stereospecific rxn?
One in which diff stereoisonmers react to give diff sgteroeisomers of the prod
What's solvolysis?
Solvents acts as Nuc-
What type of solvent does Sn1 require?
Highly polar solvents that strongly solvate ions
Is Sn1 stereospecific?
No, can attack on either face so gives both enantiomers of the prod (racemization)
Which side does Sn1 attack?
And what results?
Both front and backside
More backside since as the LG leaves, it partially blocks the front side.

Front side: retention of configuration
Back side: inversion of config
Sn2 need backside attack, what does E2 need?
Coplanar arrangement of orbitals
How do bases affect E1 and E2?
Weak bases work with E1, but E2 requires strong bases
How do substrates affect E1 and E2?
E1: 3>2
E2: 3>2>1
What are the orientations of E1 and E2?
Most highly substituted alkene
When have secondary halides, how to predict which rxn?
If have strong base, then E2/Sn2

If weak base, E1/Sn1
Which bases favor sub and which elimin.?
Sub: good nuc- w/ limited basicity

Elim: bulky strong base
In the E-Z system, which is cis, which is trans?
Cis: Z
Trans: E