CHEM 341: Organic Chemistry I at North Dakota State University. Final Exam -
Study Guide. Reactions to know. Cl. OH. HCl. OH. H. Cl. 3° carbocation best.
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
