CHEM210ReviewofSN1,SN2,E1andE2
SN2–Substitution,NucleophilicBimolecularOnestep,concertedreactionwherebothnucleophileandsubstrateparticipateinthisratelimitingstep(bimolecular)
Mechanism:
DevelopmentalProblemSet:ShowSN2productsforthefollowingreactions:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
NaClDMSO
CH3Br
NaOHCH3CN
CH3Br
KOCH3CN
CH3Br
NaCNCH3CN
CH3Br
NaCNCH3CN
CH3CH2CH2I
CH3CH2ONaDMF
CH3CH2CH2Br
Br NaClDMSO
I NaClDMSO
OTs NaClDMSO
OMs NaClDMSO
Br NaOHCH3CN
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
v.
w.
x.
Br KOCH3CH3CN
Br LiOCH3CN
Br NaCNCH3CN
BrCH3CN
OK
O
CH3CNCl KCN
CH3CNOK
O
Cl
OTsNaClDMSO
OTsNaClDMSO
BrNaCNDMF
NaSHCH3CNH
Br
NaSHHMPA
H
Cl
KOCH3CN
OBr
KOCH3CN
Br
SN1–Substitution,NucleophilicUnimolecularTwostepreactionwhereonlythesubstrateparticipatesinthisratelimitingstep(unimolecular)
Rate=k[R-X]
Mechanism:
DevelopmentalProblemSet:ShowSN1productsonly(evenwhenE1competes)forthefollowingreactions:
a.
b.
c.
d.
e.
f.
g.
h.
i.
BrH2O
BrCH3OH
BrOH
BrOH
O
I OH
NaSH
I OH
NaS
TsO OH
NaCN
H2OCl
OH
OCl
CC X
Nu
Nu C
racemic
Step 1slow
Step 2
or
fastC
X
For nucleophiles of the type H-Nuthere is a third deprotonation stepusually to give H-X
j.
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
NaSHH2O
Br
OH
NaCNOMs
OHBr
Br
OH
OHBr
H2OBr
OK
OBr
H2O
Br
H2ONaCN
H2ONaSHBr
NaCNBr
OH
OHBr ONa
O
OHBr KCN
E2–Elimination,BimolecularOnestep,concertedreactionwherebothbaseandsubstrateparticipateinthisratelimitingstep(bimolecular)
Rate=k[B:][R-X]
Mechanism:
DevelopmentalProblemSet:ShowE2productsonlyforthefollowingreactions:
a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
Br
OK
DMSO, Δ
I DMSO, ΔDBN
Br DMF, Δ
tBuOK
Cl DMF, ΔLiOH
OTf CH3CN, ΔCH3OK
CH3CN, ΔCH3OK
Br
CH3CN, ΔDBNBr
Br OK
DMSO, Δ
Cl OK
DMSO, Δ
Cl OK
DMSO, Δ
C
C X XH
B C
C
B H
anit-periplanargeometry
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
v.
Br
DMSO, ΔDBN
Br OK
HMPA, Δ
Br OK
DMSO, Δ
Br OKPh
DBU, Δ
OK
DMSO, Δ
I
DMSO, ΔDBN
Br
DMSO, ΔDBN
I
Br
OK
DBU, Δ
Ph
OTs
DMSO, ΔLDA
Ph
OTs
DMSO, ΔLDA
DMSO, ΔDBN
Br
DMSO, ΔDBN
Br
E1–EliminationUnimolecularTwostepreactionwhereonlythesubstrateparticipatesinthisratelimitingstep(unimolecular)
Rate=k[R-X]
Mechanism:
DevelopmentalProblemSet:ShowE1productsonlyforthefollowingreactions:
a.
b.
c.
d.
e.
f.
g.
h.
Br H2O, Δ
I CH3OH, Δ
OMs OH, Δ
OH, Δ
Br
H2O, Δ
Cl
OTs
CH3OH, Δ
OTs
CH3OH, Δ
OTs
CH3OH, Δ
CC X
C
Step 1slow
Step 2
fast
X
H CH
C
CHB
C
CB H
i.
j.
k.
l.
m.
n.
o.
p.
q.
r.
s.
t.
u.
v.
Br
OH, Δ
O
H2O, Δ
Br
Br
CH3OH, Δ
I
CH3OH, Δ
BrCH3OH, Δ
Br CH3OH, Δ
OTs
H2O, Δ
CH3OH, Δ
Br
H2O, Δ
Br
Cl
CH3OH, Δ
Br H2O, Δ
I CH3OH, Δ
OMs OH, Δ
OH, Δ
Br
KEYSN2a.
CH3Cl
b.
c.
d.
e.
f.
CH3CH2CH2OCH2CH3
g.
h.
i.
j.
k.
l.
m.
NaClDMSO
CH3Br
NaOHCH3CN
CH3Br CH3OH
KOCH3CN
CH3Br H3CO
NaCNCH3CN
CH3Br CH3CN
NaCNCH3CN
CH3CH2CH2I CH3CH2CH2CN
CH3CH2ONaDMF
CH3CH2CH2Br
Br NaClDMSO Cl
I NaClDMSO Cl
OTs NaClDMSO Cl
OMs NaClDMSO Cl
Br NaOHCH3CN
OH
Br KOCH3CH3CN
OCH3
Br LiOCH3CN
O
n.
o.
p.
q.
r.
s.
t.
u.
v.
w.
x.
Br NaCNCH3CN
CN
BrCH3CN
OK
OO
O
CH3CNCl KCN
CN
CH3CNOK
O
Cl O
O
OTsNaClDMSO
Cl
OTsNaClDMSO
Cl
BrNaCNDMF
CN
NaSHCH3CNH
Br
H
SH
NaSHHMPA
H
Cl
SH
H
KOCH3CN
OBr O
O
KOCH3CN
Br O
KEYSN1a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
BrH2O
HO
BrCH3OH
H3CO
BrOH
O
BrOH
O
O
O
I OH
NaSHHS
I OH
NaSS
TsO OH
NaCNNC
H2OCl OH
OH
OCl O
O
NaSHH2O
Br SH
OH
NaCNOMs CN
OHBr O
Br
OHO
n.
o.
p.
q.
r.
s.
t.
u.
OHBr O
H2OBr OH
OK
OBr
H2OO
O
O
O
+
Br
H2ONaCN CN CN
+
H2ONaSHBr SH SH
+
NaCNBr
OH
CN CN+
OHBr ONa
O
+O
O
H
H
O
O
OHBr KCN
+H
CN
CN
H
KEYE2a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
Br
OK
DMSO, Δ
I DMSO, ΔDBN
Br DMF, Δ
tBuOK
Cl DMF, ΔLiOH
OTf CH3CN, ΔCH3OK
CH3CN, ΔCH3OK
Br
CH3CN, ΔDBNBr
Br OK
DMSO, Δ
+ +major
Cl OK
DMSO, Δ
+ +major
Cl OK
DMSO, Δ+
major
Br
DMSO, ΔDBN +
major
Br OK
HMPA, Δ
Br OK
DMSO, Δ
n.
o.
p.
q.
r.
s.
t.
u.
v.
Br OKPh
DBU, Δ
Ph
+
major
OK
DMSO, Δ
I
DMSO, ΔDBN
Br
DMSO, ΔDBN
I+
major
Br
OK
DBU, Δ
Ph
OTs
DMSO, ΔLDA H
Ph
Ph
OTs
DMSO, ΔLDA H
Ph
DMSO, ΔDBN
Br
DMSO, ΔDBN
Br
KEYE1a.
b.
c.
d.
e.
f.
g.
h.
i.
j.
k.
l.
m.
Br H2O, Δ
I CH3OH, Δ
OMs OH, Δ
OH, Δ
Br
H2O, Δ
Cl
OTs
CH3OH, Δ
OTs
CH3OH, Δ
OTs
CH3OH, Δ+ +
major
Br
OH, Δ
O + +major
H2O, Δ
Br+
major
Br
CH3OH, Δ+ +
major
I
CH3OH, Δ+
BrCH3OH, Δ
n.
o.
p.
q.
r.
s.
t.
u.
v.
Br CH3OH, Δ+
major
OTs
H2O, Δ
CH3OH, Δ
Br
H2O, Δ
Br + +
major
Cl
CH3OH, Δ
+
major
Br H2O, Δ
I CH3OH, Δ
OMs OH, Δ
OH, Δ
Br