Organic Chem istry II (CHE 232-002)
Final Exam ination
April 30, 2007
Name (Print legibly):___________________________
(last)
(first)
PLEASE observe the following:
You are allowed to have scratch paper (provided by me), and a
simple model set. You do not need a calculator. Please have your
student ID card present on your desk. Read through the entire exam
before beginning and start first on the problems that seem easiest to
you. Please provide clear and concise answers to the questions
in the area provided, the back of an exam page, or on the
clearly labeled spare page.
Problem
Score
1
/60
2
/20
3
/16
4
/60
5
/45
6
/20
Total
/200
II
III
IV
1. (5 pts each, 60 pts total)
Draw the major product of each of the following reactions. Do not draw
mechanisms! If no reaction occurs, write N.R.
O
(a)
O
+ SOCl2
C
CH3CH2
C
OH
CH3CH2
Cl
O
O
O
C
C
C
(b)
CH3CH2
O
CH3
+ CH3NH2
CH3CH2
O
OH
C
OCH3
(c)
CH3MgBr
C
H3O
CH3
excess
CH3
O
Br
NaBH4
(d)
CH3
PBr3
H2O
CH3
CH3
CH3
O
(e)
NH3
NH2
H2/Pt
C
CH3
NH(CH3)
CH3
CH
CH3
CH3
1
O
(f)
1. OH–/H2O, reflux
O
2. HCl
C
C
CH3
OCH2CH3
CH3
O
SOCl2
(g)
OH
H2/Pt
AlCl3
C
+ CH3CH2OH
OH
OH
CH2CH3
O
O
(h)
+
CH2CH3
H3C
–
1. OH
2. H3O+/ heat
O
H3C
(i)
O
1. Ph2CuLi
1. CH3MgBr
+
2. H3O+
2. H3O
CH3
O
OH
Ph
2
O
(j)
NaOH/H2O
CH3 CH2 CH2 Br
PCC
H
O
O
H3C
C
Cl
C
HNO3, H2SO4
(k)
CH3
AlCl3
NO2
2. (5 pts each, 20 pts total) Provide the reagents needed to convert the
starting materials shown into the products shown.
(a)
Br
1. Ph3P
2. BuLi
3.
O
OH
CO2H
CrO3, H2SO4/H2O
(b)
or
Na2Cr2O7, etc.
O
1. NaOEt (cat)
(c)
OEt
2. H3O+
O
CO2Et
O
CO2H
(d)
1. SOCl2
N
2. Et2NH
3
3. (16 points)
(a) (8 pts) Of the carboxylic acid derivatives shown below, circle and label
the MOST reactive acylating agent, AND circle and label the LEAST
reactive acylating agent.
O
Cl
OEt
Most Reactive
O
O
O
O
O
NH2
Least Reactive
(b) (8 pts) Explain why cation A is much less stable than cation B.
Me
N
N
:
A
Me
B
A is not aromatic while B is aromatic. Complete delocalization in B allows
for greater resonance stabilization of the cation in comparison to A.
4
4. (60 points) Design syntheses of the three compounds below from the
indicated starting materials. Show how you would prepare each product
from the indicated starting material(s). Each synthesis will require two or
more steps. Show each intermediate compound and all the reagents you
will need for each step. (Don’t panic if you can’t remember the reagents
for a particular step; partial credit will be given.) Do not show reaction
mechanisms.
(a)
O
starting material
Forward reaction:
O
KMnO4
SOCl2
OH
O
Cl
1. Et2CuLi
2. H2O
O
5
(b)
Br
O
starting material
Retrosynthesis, one possibility
Cl
LiCu
+
2
O
O
CN
COOH
Br
Br
Forward:
1. CuBr
Br
LiCu
2
2. BuLi
H3O+
KCN
Br
CN
Cl
SOCl2
COOH
O
1. LiCu
2
2. H2O
O
6
(c)
O
OH
O
O
H
+
Br
H
starting materials
Forward
OH
O
HO
O
, H3O+
Mg
O
Br
Br
H
H
O
1.
O
O
BrMg
OH
O
H
H
2. H2O, H3O+
7
4. (45 points) Draw a reasonable stepwise mechanism for each of the
following reactions. Be sure that you show every bond making/bond
breaking event and be sure that your use of arrows conforms to
established conventions.
(a) (15 pts)
O
Me
NaOH, H2O
Me
O
+
O
O
O
See Textbook
8
(b) (15 pts)
O
HCl
Ph
H
C
••
Ph
N
C
N
C
H2O
Ph
NH2
Cl
Ph
Ph
C
N
C
H
NH
O
H
H
••
O
••
H
H
Cl–
Ph
C
O
H
NH
••
H
Cl
Ph
••
O
••
H
C
NH2
H
O
O
C
Ph
NH2
Cl–
C
Ph
NH2
9
(c) (15 points)
O
C
HCl, Cl2, H2O
O
C
Cl
10
6. (20 points)
(a) (10 pts) Shown below is the 1H NMR spectrum for a compound whose
molecular formula is C10H12O2. An infrared (IR) absorption for the
compound is found at 1740 cm-1.
CH3
Hb's
aromatic H's
Ha's
Which of structures A-D is most plausible for the compound? Assign the
1
H NMR spectrum by labeling appropriate groups of chemically equivalent
hydrogen atoms in the structure that you have chosen and correlate your
labels with the 1H NMR spectrum.
Ha
Ha
O
O
Hb
A
Hb O
CH3
O
B
O
O
O
C
O
D
11
(b) (10 pts) In each problem below, choose one method (optical
activity, MS, IR, 1H NMR, or 13C NMR) that will allow you to
unambiguously distinguish between the two compounds. Precisely
describe the difference that you expect to see in spectra of the
two compounds that will allow you to distinguish between the two
compounds (correct description of the difference in the spectra is
worth 4 points). Be brief (no more than two sentences).
(i)
OH
OH
CO2Et
CO2Et
Cl
Cl B
A
Method for distinguishing:
H NMR
Difference:
Only in A does one of the aromatic protons show as a singlet.
1
(ii)
OH
Cl
C
Cl
OH
D
Method for distinguishing:
H or (proton-coupled)
Difference:
1
C NMR spectra
13
Only in the 1H NMR spectrum of C does a doublet resonance (for isopropyl
methyls) and a septet (for isopropyl methine (CH) proton) appear.
Only in the proton-coupled 13C NMR spectrum of C does a doublet
resonance appear in the alkyl region (0-50 ppm) for isopropyl methine
(CH) carbon.
12