Download Exam #3

CHEM 2061 – Fall 2008 – EXAM #3 Name ______________________
1. (12 pts, 4 each) A) Give the structure of the major organic product in each of the following
SUBSTITUTION reactions, and B) predict whether the mechanism will be predominantly 1st order
(SN1) or second order (SN2). Be sure to show the correct stereochemistry of the product when necessary.
If the product is a racemic mixture, draw both enantiomers.
H
a)
HO-
Br
CH3
H3C
OTs
CH3CH2OH
b)

c)
H C C
CH2Cl
CH3CH
_
Li+
CH3
2. (10pts, 5 each) A) Give the structure of the major organic product in each of the following
elimination reactions, and B) predict whether the mechanism will be predominantly first order (E1) or
second order (E2). BE SURE TO SHOW THE CORRECT STEREOCHEMISTRY OF THE
PRODUCT WHEN NECESSARY.
a)
CH3OH
CH3CH2
CH3
Br
b)
Br
CH3
CH2CH3
H

CH3
H3C C O
K+
CH3
CH3
3. (3 pts) Which of the following is the best solvent for a SN1 reaction?
a) hexane
b) methanol
c) acetone
d) dichloromethane
4. (8 pts) Write the complete mechanism for the following acid-catalyzed hydration reaction of 2methylpropene.
OH
H3C
H
H2SO4
C C
H3C C CH3
H3C
H
H20
CH3
5.
(4 pts) Give the IUPAC name of the following compound. Be sure to use E-Z and R-S
nomenclature if necessary.
CH3
H3 C
H
6. (5 pts) Give the major product of the following reaction:
CH3
H3C C O
CH3
OTs
7.
(6 pts, 3 each) Will the following reactions go faster if the concentration of the nucleophile is
increased? (Write “Yes” if the reaction will go faster, “No” if it doesn’t go faster).
a)
H
MeO
Br
H
H3C O
+
b)
Br
CH3
O
O
CH3
+
H3 C
O
CH3
O
8. (12 pts) Consider the following E2 elimination reactions of menthyl chloride and neomenthyl
chloride:
A) Using mechanistic reasoning, EXPLAIN WHY menthyl chloride gives only 2-menthene as its
E2 elimination product.
B) Explain why 3-menthene (rather than 2- menthene) is the major product in the E2 elimination
of neomenthyl chloride.
H
H3C
CH3
Cl
CH3 CH2
O
CH3
H3C
CH3
CH3
H
2-menthene (100% yield)
menthyl chloride
H
H3C
CH3
H
Cl
CH3 CH2
O
CH3
H3C
CH3
CH3
neomenthyl chloride
3-menthene (78% yield)
+
2-menthene (22% yield)
9.
(12 pts) Bromoetherification, the addition of the elements Br and OR to a double bond, is a
common method for constructing rings containing oxygen atoms. Draw a stepwise mechanism for
the following INTRAMOLECULAR bromoetherification reaction. Hint: the mechanism is
analogous to that of bromohydrin formation – when Br and OH are added to an alkene double bond
using Br2 and H2O).
Br2
O
Br
+ HBr
HO
10. (28 pts, 4 each) Give the structure of the major organic product of each of the following
reactions. Clearly indicate stereochemistry where appropriate. If the major product is a pair
of enantiomers, only draw one of the two structures.
conc.
a)
H2SO4
OH
heat
b)
CH3
Br2
CCl4
c)
CH2CH3
CH2CH3
H2
Pt
d)
H3C
H
CH2CH3 1) O3
CH2CH3 2) CH3SCH3
3) H30+
OsO4
e)
H2O2
CH3
1) BH3.THF
f)
2) H2O2, NaOH
H2O
O
Cl
O O
g)
CH2Cl2
H