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Name: _________________________________
CHEM 332. Final Exam
Spring 2016 Prof Mary Watson
Please write your answers clearly in the boxes provided. If your answer is illegible or outside the box, it will not be graded. You may use the back of test pages for scratch work. You may use molecular models. Use of calculators, cell phones, headphones, or any other electronic device during this exam is prohibited. No notes or books may be used during this exam. You may raise your hand to ask a question if you are not sure what is being asked of you. There are 14 pages in this exam. Please check that your test has 14 pages before you begin. The last 2 pages are blank and may be used as scratch paper. Page 2 contains potentially useful IR and NMR spectral tables, as well as a periodic table. Page 3 contains the 20 common amino acids.
Question Points
1 _____ /7
2 _____ /9
3 _____ /14
4 _____ /12
5 _____ /22
6 _____ /16
7 _____ /10
8 _____ /10
Total _____ /100
1
Name: _________________________________
Approximate IR Absorption Frequencies Bond Frequency (cm–1) Intensity O–H (alcohol) 3650–3200 Strong, broad O–H (carboxylic acid) 3300–2500 Strong, very broad N–H 3500–3300 Medium, broad C–H 3300–2700 Medium C≡N 2260–2220 Medium C≡C 2260–2100 Medium to weak C=O 1780–1650 Strong C–O 1250–1050 Strong
Approximate 1H NMR Chemical Shifts
Hydrogen δ (ppm) CH3 0.8–1.0 CH2 1.2–1.5 CH 1.4–1.7 C=C–CHx 1.7–2.3 O=C–CHx 2.0–2.7 Ph–CHx 2.3–3.0 ≡C–H 2.5 R2N–CHx 2.0–2.7 I–CHx 3.2 Br–CHx 3.4 Cl–CHx 3.5 F–CHx 4.4 O–CHx 3.2–3.8 C=CH 4.5–7.5 Ar–H 6.8–8.5 O=CH 9.0–10.0 ROH 1.0–5.5 ArOH 4.0–12.0 RNHx 0.5–5.0 CONHx 5.0–10.0 RCOOH 10–13
Approximate 13C NMR Chemical Shifts Carbon δ (ppm) Alkanes
Methyl 0–30 Methylene 15–55 Methine 25–55 Quaternary 30–40
Alkenes C=C 80–145
Alkynes C≡C 70–90
Aromatics 110–170 Benzene 128.7
Alcohols, Ethers C–O 50–90
Amines C–N 40–60
Halogens C–F 70–80 C–Cl 25–50 C–Br 10–40 C–I –20–10
Carbonyls, C=O R2C=O 190–220 RXC=O (X = O or N) 150–180
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CHEM 332. Spring 2014 Organic Chemistry University of Delaware Prof. Donald Watson
Natural Amino Acid
H2N
OH
O
O
OHH2N
O
OH
OHO
H2NO
OH
OH
H2NO
OH
H2NO
OH
NH
HN NH2
H2NO
OH
NH2
H2NO
OHN
NH
H2NO
OH
NH
H2N
Me
O
OHH2N
O
OH
Me Me
H2NO
OH
Me
Me
H2NO
OH
MeMe
H2N
NH2
O
O
OHH2N
O
OH
NH2O
H2NO
OH
OH
H2NO
OH
Me OH
H2NO
OH
SH
H2NO
OH
S Me
H2NO
OHNH O
OH
Aspartic acid Glutamic acid Asp Glu D E
pKa= 3.7 pKa= 4.3
Acidic Amino Acids Basic Amino Acids
pKa'= 12.5pKa'= 10.5 pKa'= 6.1
Arginine Lysine Histidine Arg Lys His R K H
Phenylalanine Phe
F
Hydrophobic or Aliphatic Amino Acids
Alanine Valine Leucine Isoleucine Ala Val Leu Ile
A V L I
Serine Threonine Tyrosine Ser Thr Tyr
S T Y
pKa= 13.0 pKa= 13.0 pKa= 10.1
Polar/ Hydrogen bonding Amino Acids
Sulfur containing Amino Acids
Methionine Cysteine Met Cys
M C
pKa= 8.3
Flexible/inflexible Amino Acids
Glycine Proline Gly Pro
G P
Glutamine Tryptophan Gln Try
Q W
Asparagine Asn
N
3
Name: _________________________________
1. (7 points) Using the template below, please complete the structure of the peptide DELAWARE in its major protonation state at pH = 7. Show stereochemistry.
NHN
ONH
O HN
O
O
NH
HN
ONH
O HN
OO
O
2. (9 points) Please fill in the missing reagents for each transformation below. In some cases, more than 1 step may be required.
CH3
Br
CH3
O
CH3CO2t-Bu
CH3
O
CH3
CH3
NH2
CH3
4
Name: _________________________________
3. (14 points) D-Mannopyranose exists as a 66:34 ratio of its α and β anomers at 25 °C in H2O. (a) Please draw the lowest energy chair conformations of α-mannopyranose and β-mannopyranose.
O OH
OHOH
HO
HO
D-mannopyranose
α-D-mannopyranose β-D-mannopyranose
(b) Why is the α-anomer favored?
(c) The interconversion of α-mannopyranose and β-mannopyranose occurs via the open (or acyclic) form of mannose. Please draw a reaction coordinate diagram for the interconversion of α-mannopyranose and β-mannopyranose. You may assume a single transition state (no intermediates) between the cyclic and each acyclic form of mannose.
5
Name: _________________________________
4. (12 points) (a) Please draw a reasonable arrow-pushing mechanism for the following reaction.
H3CO CH3
CH3
+
CO2CH3
CO2CH3
ΔH3CO
CH3
CH3
CO2CH3
CO2CH3
*
*
(b) Please re-draw the product, showing the stereochemistry at each of the starred carbons (*).
H3COCH3
CH3
CO2CH3
CO2CH3
*
*
6
Name: _________________________________
(4 – continued) (c) For each pericyclic reaction in your mechanism, please explain why the thermally allowed pathway leads to your predicted stereochemistry in part (b). You may use Frontier Molecular Orbital Theory and/or Woodward-Hoffman Conservation of Orbital Symmetry in your explanation.
7
Name: _________________________________
5. (22 points) (a) Please fill in the missing reagents and intermediates in the synthesis below.
Me3Si
OH
Me3Si
O
O
H3C LiN(i-Pr)2(t-Bu)Me2Si–Cl
–78 °C
C, C19H36O2Si2
1) Δ Me3SiO
OH
Me3SiO
OCH3
CH3
A B
D E
2) H3O+
(b) Please draw a reasonable arrow-pushing mechanism for the transformation of B to C.
8
Name: _________________________________
(5 – continued) (c) Please draw a reasonable arrow-pushing mechanism for the transformation of C to D.
9
Name: _________________________________
6. (16 points) Please fill in the missing reagents for each transformation below. In some cases, more than 1 step may be required.
Me2N
NC
MeMe
Me
MeCN
CH3OH
O
H2N
O
OHH3C
O
OH3C CH3
CH3
Me2N
10
Name: _________________________________
7. (10 points) Please provide a synthesis of 1 from benzene. You may use any additional reagents you need.
OH3C
CH3
1
11
Name: _________________________________
8. (10 points) Please provide a synthesis of 3 from 2. You may use any additional reagents you need.
H
O
BrNH
CO2H2 3
12
Name: _________________________________
This page was intentionally left blank and may be used for scratch paper.
13
Name: _________________________________
This page was intentionally left blank and may be used for scratch paper.
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