Name _______________________
Page 1
A. Reaction analysis: provide the requested information in each of the following chemical
transformations. Show all products unless otherwise indicated, and if any reaction results in
a stereoisomeric mixture, draw one and indicate "+ enantiomer," "+ diastereomer," or "+
more than one stereoisomer" in the box.
+diastereomer
(ii)
(a) (i)
top chiral center is
I. (29 points)
unchanged
top chiral center is unchanged
OR
1. BH3
OR
HO
note ethyl and
OH on
opposite sides
HO
H2
Pt
2. H2O2
NaOH
H2O
4
+ diastereomer
(b) (i)
4
(ii) Draw all products
OH
Na
1) NaNH2
NH3
O
H2O
2)
H2SO4 (cat.)
Br
Br
3
(c)
4
Draw all organic products in their appropriate boxes:
(i)
(ii) 1H NMR: 1 signal
O
H2
Pd/CaCO3
PbO
1) O3
2) Zn
1H
NMR: 2 signals
O
O
O
O
O
4
3
(d) Treatment of the following compound with a strong base, DBU, yields a single kinetically
and thermodynamically favored product
(ii) Using a Newman projection, draw
the kinetically favored conformation of
the bond of interest; view so that the
carbon with the leaving group is in
back.
(i) Draw the product
bond of interest
Br
N
C
C
H
H
N
Br
H
H
3
4
Name _______________________
Page 2
Cyanogen bromide (BrCN) is a good source of electrophilic bromine. When used in addition
reactions, it displays the same regioselection and stereoselection predicted for reagents like
HOCl or HOBr. For the following reaction, one product is drawn for you. Draw the other
product(s) predicted to form.
II. (25 points)
(a)
Br C N
CN
Br
Br
CN
CN
CN
Br
+
Br
3
Draw the complete, two step mechanism for the production of the product shown above.
(b) You should show stereochemistry whenever it is appropriate.
Br must be dashed initially to give the product shown above
C N
CN
Br C N
Br
Br
3 pts each step
3 pts for intermediate: must show charge and stereochem for the Br
9
(c) Treating the product shown above with a strong, bulky base leads to a single elimination
product. Draw the complete curved-arrow mechanism for this E2 reaction, using the
appropriate chair conformational drawing. Then draw the elimination product.
H3C
CN
H3C
Br
H3C
H3C
(i) chair conformer and curved arrow
mechanism
CH3
C
K
O
CN
H
O
CH3
C
(ii) elimination product
CN
H
H
OH
H
must show stereochem on
CN
3
Br
6
3 pts mech 3 pts chair
(d) Knowing cyanogen bromide's (CNBr) stereoselection and regioselection (described above)
draw the structures of the two stereoisomeric products predicted to form in the following
reaction.
Br
Br
O
Br C N
O
CN
O
CN
2 points each
Connectivity must be correct for any credit
if they are not stereoisomers, no credit
4
Name _______________________
Page 3
III. (25 points)
Complete the following reactions as directed. Show the major organic product(s) unless
otherwise specified. If a product forms as a stereoisomeric mixture, draw one and write
"+enantiomer" or "+diastereomer" in the box.
(a)
(ii)
C10H12O
(i) C10H10O
The optically pure starting
material contains an R
stereosite
Br
Br
Br
Br2
H2SO4
OH
Br
heat
(R)
+ enantiomer 1pt
only this product
4
3
(i)
(b)
(ii) Provide the IUPAC name,
including stereochemistry when
needed, for Compound 1.
+ Diastereomer
same
H2
Pt
(S)
dashed OR wedged
or 4S
(S)
Compound 1
2-hexene also
(S)-2,3,4,5-tetramethylhex-2-ene
2pts/error
4
4
B. The starting material shown in the conformational drawing below is treated with two very
different reagents. Each reaction yields a mixture of two products - draw each of the
products and describe how the products are related.
5
O K
OH
enantiomers
The products are __________________ of each other.
I
H3C
O
O C
O
H
H3C
C
O
O
O C
K
polar solvent
diastereomers
The products are __________________ of each other.
5
Name _______________________
Page 4
IV. (31 points)
A. Consider the reaction scheme below, and provide the missing information. Note that
stereochemistry is not considered here.
(a)
C8H12
O
H
KMnO4 or OsO4
H3O
H2O
O
heat
O
a single reagent
H
2
3
Elimination with rearrangement
(b) It has been proposed that the elimination product forms as a result of several mechanistic
steps, and resonance stabilization plays an important role in the rearrangement. Using H3O+
and H2O as needed, draw the most straightforward curved arrow mechanism for this
transformation, and show the resonance effect clearly.
may be that the shift goes directly to the resonance with O+
resonance
H
H
O
O
H
O
O
O
H
H H O H
H
H
H2O
O
either arrows
depending on which contributor is used
H
O
O
H
2 points/intermediate (2 more for resonance)
2 points/mechanism (per step)
Grading stops when a chemically illogical step is shown
16
B. For each of the following reactions, draw the connectivity of major product(s) only, and then
address the stereochemistry by checking the best box.
3pts
1) Na/NH3
This product forms as:
Cl
X
a racemic mixture
2) Cl2
a diastereomeric mixture
a mixture of 3 or more
stereoisomers
5
Cl
meso only forms
O
H3C
C
2 pts
a single compound
This product forms as:
3pts
O
O
2 pts
a single unique compound
H
a racemic mixture
O
O
X
a diastereomeric mixture
a mixture of 3 or more
stereoisomers
5
Name _______________________
Page 5
Each of the following reactions produce a mixture of uncharged products. Draw each of
these individual product(s) (with stereochemistry and connectivity clearly shown) in their
appropriate boxes.
V. (30 points)
Optically active product(s)
(a)
OCH3
CH3OH
OCH3
Optically inactive product(s)
OCH3
(S)
(S)
HCl (cat.)
(R)
(S)
H3CO
H3CO
6
Contains an R stereocenter
(b)
Contains an S stereocenter
1) B2H6
HO
HO
2) NaOH
H2O2/H2O
(S)
(R)
6
C6H8
(c)
NMR: 4 signals C6H8
13C
NMR: 6 signals
CH3OH
O
S
13C
heat
O
O
6
Circle all the products that are achiral (optically inactive):
(d)
OsO4
HO
OH
HO
-1 pt for each missing circle
(e)
Z configuration
Br
OH
6
E configuration
NaOCH2CH3
6
3 pts per side - both products must be drawn