CHEM 341: Organic Chemistry I
at North Dakota State University
Final Exam - Study Guide
Reactions to know
Substitution of Alcohols
R
+
OH
HX
R
+
X
HOH
SN1 Substitution
H
HCl
OH
- HOH
OH
Cl
Cl
3° carbocation best
2° carbocation ok
SN2 Substitution
H
HCl
OH
1° will not form carbocation
R
OH
+
SOCl2
S
Cl
Cl
R
+
Cl
SO2
+
HCl
Cl
O
Cl
- HOH
OH
O
Cl
S
OH
O
H
Cl
Cl
SN2 Substitution - will work with 1° and 2° alcohols, not 3° alcohols
R
OH
+
PBr3
R
Br
H3PO3
Br
Br
P
+
Br
Br
Br
OH
Chem 341 Final Exam Study Guide!
P
O
H
Br
page 1!
Br
spring 2012
Free Radical Halogenation
+
CH4
light
Cl2
CH3Cl
or heat
Initiation
Cl Cl
Propogation
Cl
+
Cl
+
Cl
H
H
H
H +
Cl
H
C
H
H
H
H
C
H
+
Cl
Cl
H
H
Termination
H
H
C
H
C
C
Cl
+
Cl
H
H
+
Cl
H
H
C
Cl
H
Elimination of Alcohols
H
R2C
OH
H+
CR2
CHR2 +
R2HC
HOH
E1 Elimination - proceeds through carbocation, 2° and 3° alcohols
H
OH
O
H3PO4
H
H
-H2O
H
H
H2PO4
E2 Elimination - 1° alcohols, requires anti-periplanar arrangement
H
OH
H3PO4
H
Chem 341 Final Exam Study Guide!
O
H
H
H2PO4
page 2!
spring 2012
Elimination of Halides
H
R2C
X
RO
CR2
R2C
+
CR2
HOR
E2 Elimination - 1°, 2° or 3° halides with strong base
requires anti-periplanar arrangement
Cl
K+ -OCH3
+
KCl
+
HOCH3
H
E1 elimination can occur under neutral conditions only with 3° halides
Electrophilic Addition to Alkenes
A
A+
B-
B
or
A
A
overall equivalent
reagents
notes
H2O (H+ cat)
BH3
then H2O2/OHHX
H+
BHOHX-
Markovnikov
X2
X+
X-
bridged, anti addn
X2/H2O
X+
HO-
bridged, anti addn, Markovnikov
A+
H+
OH+
H3PO4
Markovnikov
syn addn, anti-Markovnikov
OH
H2O
H
H2O
250°C Most stable intermediate
Lower energy pathway
Chem 341 Final Exam Study Guide!
page 3!
H
Markovnikov Addition
spring 2012
H
H3C
C
H3C
C
+
H
H3C
HBr
H
C
C
H3C
Br
H3C
H
C
H3C
H
Br
C
H
H
Markovnikov Addition
Most stable intermediate
Lower energy pathway
Br
Br-Br
Br
A bromonium
Br
Bromide can only come from the
bottom and kick off the bromine on
the top. This reaction forms the trans
product selectively.
Br
Br
Br-Br
CH3
H2O
H2O
CH3
Br H
CH3
OH
Markovnikov Addition
even if there is no full carbocation
Hydroboration and Hydrogenation
1) BH3
H
BH2
2) H2O2 / NaOH
H
OH
anti-Markovnikov
hydration
syn addition
H2
Pd/C
H
H
Chem 341 Final Exam Study Guide!
page 4!
syn addition of H2
spring 2012
Reduction (Hydrogenation) Reactions
H2
H
H
Pd/C
H
H
H2
Pd/C
H
H2
H
H
Lindlar's Catalyst
Pd(OAc)2
quinoline
on CaCO3
Lindlar's Catalyst
stops at alkene
Li
H
H
trans alkene
NH3
H
Electrophilic Addition Reactions
cat. HgSO4
H2SO4
H 2O
Ketone
O
Cl
HCl
1 equiv
Br
Br2
1 equiv
HCl
1 equiv
Cl
Br2
1 equiv
Br Br
Br
Br
Cl
Br
Oxidation Reactions
O3
then Zn/HOAc
O
+
O
O
O3
then
OH
Zn/H+
+
HO
O
O
Cl
O
mCPBA
O
H
O
Chem 341 Final Exam Study Guide!
epoxidation
page 5!
spring 2012
Substitution Reactions
δ+
H 3C
NaNH2
H
S
Cl
O
Cl
OH
O
H
Br
S
Cl
Cl
Br
Br
Br
Br
P
CH3
Na
Cl
O
δBr
Br
Br
OH
O
H
P
Tos-Cl
pyridine
O
S
OH
O
Cl
O
Tos
Tos-Cl
Elimination Reactions
Br
Br
KOH
or NaNH2
Br
or
Br
KOH
or NaNH2
Br
can be prepared
by Br2 addition to
an alkene
a vinyl bromide
You should know the mechanistic details of SN1, SN2, E1 and E2 mechanisms and what factors influence
substitution vs elimination pathways. There are a number of different nucleophiles and electrophiles that
participate. You should be familiar with those and be able to recognize what various reactants do.
Chem 341 Final Exam Study Guide!
page 6!
spring 2012
SN1
SN2
SUBSTRATE
3° >> 2° > 1°
1° > 2° >> 3°
NUCLEOPHILE
Weak OK
Strong
LEAVING GROUP
Stable Anions
Stable Anions
STEREOCHEM
Racemic
100% inversion
SOLVENT
Polar Protic
Polar Aprotic
R-X
SN1
E1
SN2
1°
X
X
favored
2°
ok
ok
favored in
protic solvents
no base
3°
N3
Br
Cl
CN
can compete
witn SN1
favored with
strong base
favored with
strong or weak
base
X
Strong Bases
SH
SR
OH
OR
NH2
bulkier is less nucleophilic
C CR
Chem 341 Final Exam Study Guide!
favored with
strong base
favored with
strong
nucleophile
Good Nucleophiles
I
E2
page 7!
spring 2012
Preparation of Conjugated Dienes
NBS
peroxides
KOt-Bu
t-BuOH
Br
Note that the allylic position is especially easy to form free radicals. Halides can be eliminated under base
conditions to form conjugated dienes. Alcohols can be eliminated under acidic conditions.
Reactions of Conjugated Dienes
HBr
H
H
H
not formed
Br
H
H
1,2-addition
Br
1,4-addition
Kinetic Control
0 °C
71%
29%
Thermodynamic Control
40 °C
15%
85%
Diels-Alder Reactions
+
CO2CH3
diene
cyclic transition state
dieneophile
CH3
CH3
+
CH3
CH3
O
CH3
dieneophile
exo transition state
CH3
opposite
sides
O
endo product
major
same
side
endo transition state
H
CH3
H
H
H
opposite
sides
O
Chem 341 Final Exam Study Guide!
H
CH3
H3C
H
H
O
exo product
minor
H
+
H
H
H
H3C
CO2CH3
CO2CH3
O
H
secondary orbital
interaction with the
carbonyl pi-bond
lowers the energy for
this transition state
page 8!
H3C
O
H
H
H
H
same
side
CH3
O
spring 2012
Electrophilic Aromatic Substitution
Br2
FeBr3
H
Br
Br
NOT formed
H
Br
NEED TO KNOW MECHANISM
Br
H
Br
Br2
FeBr3
H
Br
H
Br
Br
-HBr
Br
Br2
Cl2
FeCl3
Br
Br
FeBr3
+
+ FeBr4
electrophile
Cl
Cl2
Cl
FeCl3
+
+ FeCl4
electrophile
I2
CuI2
I
I2
I
CuI2
+
+ CuI3
electrophile
HNO3
H2SO4
NO2
O
HO N
O
+
H2SO4
O N O
electrophile
Fuming
SO3
H2SO4
SO3H
O
O S
O
+
O
O S
OH
H2SO4
electrophile
O
R-Cl
AlCl3
R
+
Cl
O
Chem 341 Final Exam Study Guide!
page 9!
AlCl3
88%
spring 2012
Activating
Electron Donating Groups
Deactivating
Electron Withdrawing Groups
ortho, para directors
OR
meta directors
NO2 strongest (resonance)
strongest (resonance)
NR2
SO3H
SR
O
alkyl
weakest (inductive)
X weak
ortho, para directors
but deactivating
R
CN
Other Reactions of Benzene and Substituents
CH3
O
C
KMnO4
O
O
C
KMnO4
OH
OH
O
C
KMnO4
KMnO4
OH
No Reaction
O
N Br NBS
Br
O
O
Ph
O
O O
Ph
O
H2
Zn(Hg)
Pd/C
H3O+
R
H2
Na / NH3
R
Pt
2000 psi
Chem 341 Final Exam Study Guide!
page 10!
spring 2012