ch 6 o chem Flashcards
good leaving groups
TsO->I- >Br- > Cl- >F-> H2N >H2O >RN
F doesn’t do sn2
h20 h2n and rn dont do sn2 or sn1
what makes a good leaving group
weak base or stable anion or neutral when it leaves
electronegative
Rate for SN2
r8 = K [R-X] [Nu]
how to tell order from a graph
if one [ ] stays the same and the other increases its 1
explain how the bond breaks in the SN2
HOMO of the nucleophile (its lone pair) overlaps with LUMO from substrate so the leaving group bond breaks heterolytic bond cleavage R->S S->R
SN2 energy diagram
1 step exo or endo
x axis: rxn coordinate
y axis: potential energy
If nucleophile has no - charge in SN1 rxn? in SN2 rxn?
SN2: extra step at the end to make product neutral
ex: you get rid of one of the h by adding h2o into it (makes h30 and gives a .. to product)
sn1= same
rate for sn1
r8 = K [ R-x]
because breaking the R-X bond is the slowest step
SN1 energy diagram
many steps (bumps) step 1 transition state (peak) is the highest as it takes most energy (r8 determining)
x axis: rxn coordinate
y axis: potential energy
what makes a carbocation good and reactive for SN1
stability 3º > 2º > 1º > methyl more polarized bonds is better resonance hyperconjugation
more stable= faster
SN1 rxn products
it makes 2, 50:50, racemic
if there’s chiral centre it ends with R and S
SN1 with a chair
make sure chair is most stable version, if its not flip it
and then draw the chair in cis and trans (just make the nu be in once and out the next)
solvolysis
hydrolysis
methanolosis
solv: when you have your nucleophile be the solvent
hydrolysis : h2O
methanolysis: MeOH -> it gives MeO on the thing
which dont do sn1 or sn2
which dont do sN2
dont do either:
allkyl (tripple bond)
aryl (aromatic with a -x)
vinyl =-x
dont do SN2:
R-F, R-OH, R-NH2, R-OR
if nucleophiles all have same nucleophilic part (ex all have O their strength is based off what?)
its based of basicity (+basic = best, fastest, most likely to do sn2)
