KEY
Name _______________________
Page 1
I. (28 points)
Complete the f ollowing reactions as directed. Transformations requiring sequential experimental steps
should be numbered appropriately. Show the major organic product(s) unless otherwise specif ied.
Abbreviations f or reagents are not allowed. If a product f orms as a stereoisomeric mixture, draw one
and write "+enantiomer" or "+diastereomer" in the box.
A.
HO
1) Na, NH3
+ Na Br + H2
H
2) OsO4
C
C C
CH3
OH
1) NaH
C
H
4
H
C C CH3
only this product continues
2) CH3Br
4
H2
CH2CH2CH3
Pd/C
B.
4
H3C
H3C C O
H3C
K
Br
O
O
O
O
H
only this alkene
p roduct!
4
4
C.
O
OH
1) O3
CH2CH3
OH
2) H2O2
OH
+
O
CH2CH3
H
Ph
H
Ph
1) NaNH2
CH2CH3
2) PhCH2I
O
4
H
Ph
CH2Ph
4
KEY
Name _______________________
II. (24 points)
Page 2
Compound
B
undergoes
bimolecular
elimination
when
treated
with
NaOCH2CH3 to f orm a single,
A.
major product.
i) Draw the curved arrow mechanism for this reaction using the chair conf ormation that gives the
fastest rate of elimination, and
ii) Draw the elimination product (Product C).
i) curved arrow mechanism f or reaction with NaOCH2CH3
CH3CH2O
CH2CH3
Br
H
CH3CH2OH
C
H
H3C
H
HC
CH3
H3C
H
CH2CH3
CH2CH3
H
NaOCH2CH3
H
Br
C
H3C H CH3
CH3
Compound B
8
B.
CH2CH3
ii) Major elimination product
4
Product C
i) Compound D is a stereoisomer of Compound B. The rate of bimolecular elimation
of Compound D to f orm Product C (above) is expected to be
Br
the same as
f aster than
slower than
(circle one)
the rate of bimolecular elimation of Compound B to form Product C.
H3C
C
H
CH3
Compound D
2
ii) In one or two sentences, explain why the rate would or would not change as
indicated in part i above.
The isopropyl group would be equitorial on the ring in Compound D f or the
conf ormation that allows E2. Since that is a more stable conformation than the
conf ormation shown f or Compound B, the molecule would spend more time in that
conf ormation and E2 would occur more rapidly.
4
diastereomers
iii) Compound B and Compound D are best described as being _______________________________
of each other.
2
C.
The f ollowing results in more than one product. Write all predicted products of this reaction in the
box provided. No rearrangements were observed.
CH3
H3C
CH3
CH3
CH3CH2OH
H3C
CH3
Br
H
CH3
H
+
OCH2CH3
H3C
CH3
H
OCH2CH3
4
KEY
Name _______________________
Page 3
III. (34 points)
A. Metolachlor is a potent herbacide used to control a variety of weeds. An almost 10-year-old study
(Tetrahedron, 1997, 53, 10513) has shown that, under certain conditions, this compound undergoes an
intramolecular SN2 reaction that produces a compound with a very good positive-oxygen leaving group
(Compound J). One of the things observed in some intramolecular SN2 reactions is that typically poor
oxygen nucleophiles, such as ethers, can participate in these reactions. Surprisingly, Compound J can
participate in a second SN2 reaction with water.
Complete the reaction, including curved arrow mechanisms f or each step and the structures of
Compounds J and K.
O
Structure of Compound J and
arrows f or intermolecular S N 2
arrows f or intramolecular S N 2
H
CH3
O
N
Cl
O
O
N
N
O
O
H
O
+
other organic p roduct
CH3OH
2
metolachlor
6
Compound J
4
Compound K
B. i) Fill in the f ollowing boxes with the structures or names indicated.
H3C
3,3-dimethyl-1-butene
CH3
2-chloro-2,3-dimethylbutane
C
H3C
CH3
H
C
H3C
C
H3C
HCl
CH3
H3C
HCl
C
H
C
+
C
+ enantiomer
H3C
Name the above molecule
H
Cl
CH3
C
H
(S)-2-chloro-3,3-dimethylbutane
CH3
4
6
4
ii) In the space below, provide the complete, step-wise, curved arrow mechanism for the transformation of
3,3-dimethylbutene to 2-chloro-2,3-dimethylbutane.
H
H3C
CH3
C
H
Cl
H3C
H
C
H3C
Cl
C
CH3
C
H3C
H
H
C
H
CH
H
H3C
H3C
C
H3C
C
CH3
H3C
C
H
Cl
CH3
CH3
C
H
CH3
8
KEY
Name _______________________
Page 4
IV. (28 points)
When Compound A is treated with water in the presence of an acid catalyst, two uncharged
A. stereoisomeric products result. Draw these products, showing appropriate stereochemistry.
i)
CH3
CH3
OH
H2O
H2SO4( cat)
H3C
OH
CH3
+
H3C
H3C
Compound A
3
3
diastereomers
ii) The two products of the above reaction are best described as being ___________________________
of each other.
2
B. The f ollowing reactions yield products that are stereoisomeric mixtures (ignore all byproducts) -
complete these reactions, showing stereochemistry clearly f or one product. Also, answer the questions
about the stereoisomers that f orm.
i)
OCH3
HO
H
2. H2O2/NaOH H3CH2C
H3C
H
Describe the products: ( check all that apply)
a diastereomeric pair
a mixture of >2 stereoisomers
x a racemic mixture
1. BH3
OCH3
ii)
I
H
HI
H3CH2C
H3C
iii)
CH3
CH2CH3
draw the reactive intermediate that leads
to the product you draw in the next box
CH3
CH3
CH3OBr
x all are chiral molecules
at least one is achiral
Describe the products: ( check all that apply)
a diastereomeric pair
x a mixture of >2 stereoisomers
x
a racemic mixture
all are chiral molecules
at least one is achiral
6
Draw one of the stereoisomeric products
H3CO
Br
6
CH3
H
Br
4
4
KEY
Name _______________________
Page 5
V. (26 points)
A. Provide the missing inf ormation in the multi-step syntheses below. Include stereochemistry where
needed. Also remember to number steps if more than one discrete transformation is represented by a
single arrow.
i)
H3C
1. B2H6
2. H2O2
O
O
3. O
H3C S Cl
CH3
O
+
3
N
O
NH
(CH3)2NH
S
CH3
3
O
H3C S O
O
ii)
CH2CH3
C
O
1. H3C S Cl
O
HO
CH3 2. NaBr
H
single stereoisomer
CH2CH3
NaCN
N
2
CN
C
H
Br
CH3
2
4
H
H3CH2C
CH3
single stereoisomer
B. When the Compound D was dissolved in ethanol many products resulted, however no evidence of
rearrangement was f ound. Using the inf ormation given, predict these product(s), drawing them in the
appropriate spaces.
all products having molecular f ormula C 9H 18O2
Br
CH2CH3
+
OCH2CH3
CH2CH3
CH3CH2OH
CH2CH3
OCH2CH3
+
O
O
Compound D
O
6
all products with a molecular f ormula of C 7 H 12O
H
CH3
CH2CH3
O
+
O
H
+
CH3
O
6