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: _________________________________

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13

Name: _________________________________

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