Chemistry 221 - Test 2 Review Sheet
(Chapters 6-9)
1. Fill in the missing starting material(s), reagent(s), or product(s). Show all reasonable answers. Name each reaction.
Hydrohalogenation
HBr
or
Br
Ozonolysis
O+
O
1. O3
2. Zn, H3O+
Oxidation
H
KMnO 4
(acidic)
H
O
OH
+ CO2
Hydration
Oxymercuration/Demercuration
1. Hg(OAc)2, H2O
OH
Hydroboration/Oxidation
1. BH3, THF
2. H2O2, H2O, OH-
2. NaBH4
OH
Hydroxylation
OH
1) OsO4 , pyridine
(R,R and S,S)
2) NaHSO 3, H 2O
HIO4
O
+
O
OH
Hydration
O
Hydroboration/Oxidation
1) BH3, THF
2) H2O2, OH -, H2O
HgSO4
HSO 4, H 2O
Ozonolysis
O
Oxidation
1) O3
2) H3O+
Reduction
Na, NH 3
OH
+
KMnO4
(acidic)
CO2
O
Halogenation
Cl 2
Dehydrohalogenation
excess
Cl
KNH 2
Cl
O
O
Os
2. Draw the cyclic osmate for the oxidation of
.
O
O
OH
O
+
CO2
3. Write all possible products and the mechanism for the reaction:
(consider Markovnikov’s rule and rearrangement)
HBr
+
Br
+
Br
Br
HBr
Br
+
+
Br
Br
H
H
Br
+
Br
+
major
H
H
+
1,2-hydride shift (rearrangement)
+
+
minor
H
Br
Br
bromide anion bonds to one of
the carbocations forming a mixture
of 3 products (only 1 shown here)
transition states
The rearrangement product is consistant with formation
intermediate such as a carbocation.
The distribution (relative amounts) of products is
consistant with carbocation stability.
Relatively stable carbocations, analogous to those
postulated in the mechanism, have been detected.
Draw a potential energy diagram for the overall reaction labeling the pertinent sites.
Energy (∆ G)
What evidence do we have to support this mechanism?
of an
intermediate
carbocation+Br- products
reactants
(halide)
(alkene+HBr)
Reaction Progress
4. Name:
cis,cis-11-bromo-2-propyl-1,4,9-undecatriene
(5E,8Z,12E)-12-bromo-2,8-dichloro-6-methyl1,5,8,12-tetradecatetraene
Br
6-bromo-1,4-cycloheptadiene
Br
Cl
Cl
Br
Br
3-bromo-2,2,6-trimethyl-4-octyne
6-cyclobutyl-2-hexyne
6-hexyl-11-isopropyl-3,8-tetradecadiyne
5. Rank the following molecules by the relative stability of the pi bonds (#1 most stable).
4
3
6. Why are trans-alkenes more stable than cis-alkenes?
Less steric strain
1
2
7. Draw the rearrangement product (if any) for:
HBr
Br
None
Br
HBr
HBr
8. Why do propagation steps occur as many as 10,000 times before termination?
Propagation occurs when a radical (which is a very reactive intermediate) reacts with a reactant to form a
new radical. This newly formed radical can react with another molecule of reactant forming yet another
radical and perpetuating the cycle. Termination of the cycle occurs when two radicals react together.
Since there is very little radical present it is much less likely for to radicals to collide than for one radical
to collide with a reactant.
How does a termination step stop the chain reaction?
When two radicals react together a stable product is formed. Since no new unstable radical is formed the
reaction stops.
Assign the R and S configuration to each of the following stereogenic centers. Which two represent the same molecule.
Br Cl
S CH
CH 3 R
3
H H
Rank the relative acidities (1 as highest) of:
H
Br R
CH 3
R Cl
CH 3 H
R
R CH
H
3
Cl Br
CH 3 CH 3
R
S H
H
CH 3 H
Cl
Br
Water and alcohol have approximately equal acidities
H
6
O-H
2
H
N
Using 1-butyne and 1-iodopropane (and any inorganic reagents) prepare 3-heptyne.
NaNH2
I
Na
4
H
3
H
5
1
H2 O