OChem2 Old Exams 3. (16 points) Give the expected major product from each step of the following reaction sequence. No need to show any mechanisms. (Klein Chapter 13) 4. (9 points)

OChem2 Old Exams

Practice Exams From 2013-2015

1

Chemistry 3720 Practice Exam 1 Name: This exam is worth 100 points out of a total of 600 points for Chemistry 3720/3720L. You have 50 minutes to

complete the exam and you may use the attached spectroscopy sheet as needed. Good Luck.

1. (8 points) Give the major final products from the following and explain the different regiochemical outcomes

in terms of the mechanism(s) operating.

(Klein Chapter 14)

2

2. (20 points) Give the major organic product(s), including any stereochemical issues, expected from each step

in the following reactions. You do not have to show any mechanisms.

(Klein Chapters 13 and 14)

3

3. (16 points) Give the expected major product from each step of the following reaction sequence. No need to

show any mechanisms.

(Klein Chapter 13)

4. (9 points) Give the expected final product(s) formed in each of the following cases. (Klein Chapter 14)

4

5. (7 points) Give the expected major product formed under the following reaction conditions, and then a detailed

mechanism for the conversion. How would you tell the product is an alcohol by IR spectroscopy?

(Klein Chapters 13-15)

6. (8 points) A recently isolated microbial metabolite is found to have the empirical formula C4H7O and its mass

spectrum shows M+ = 142. Significant signals are seen in the IR spectrum at 1740 and 1650 cm-1. The 1H

NMR spectrum, collected in CDCl3, is given below. Provide a structure for the organic compound that

matches the data, and then match the protons in the molecule to the 1H NMR signals. (Klein Chapter 15)

Unsaturation number = [#C atoms – ½#H atoms – ½#Halogen atoms + ½#N atoms] + 1

1H NMR (ppm): 1.06 (d, 6H, J = 7.1 Hz), 1.36 (t, 3H, J = 7.0 Hz), 2.52 (octet, 1H, J = 7.1 Hz),

4.20 (q, 2H, J = 7.0 Hz), 5.83 (d, 1H, J = 16.0 Hz), 6.88 (dd, 1H, J = 7.1, 16.0 Hz)

5

7. (12 points) Provide a retrosynthetic plan for the molecule below that uses only the given starting materials as

sources of carbon. Then give a detailed synthesis of the compound that shows each product formed along the

way. You have access to all of the usual reagents in the lab (HBr, HNO3, NaBH4, Zn, Mg, etc.), as well as

techniques for separating isomers and byproducts (i.e. distillation, chromatography, etc.) as needed.


6

8. (20 points) Give the major organic product(s) expected from each step in the following reactions. You do

not have to show any mechanisms. (Klein Chapters 13 and 14)

1

Chemistry 3720 Practice Exam 1 - Key Name:

This exam is worth 100 points out of a total of 600 points for Chemistry 3720/3720L. You have 50 minutes to


1. (8 points) Give the major final products from the following and explain the different regiochemical outcomes

in terms of the mechanism(s) operating.

(Klein Chapter 14)

2


in the following reactions. You do not have to show any mechanisms.

(Klein Chapters 13 and 14)

3



(Klein Chapter 13)

4. (9 points) Give the expected final product(s) formed in each of the following cases. (Klein Chapter 14)

4

5. (7 points) Give the expected major product formed under the following reaction conditions, and then a detailed

mechanism for the conversion. How would you tell the product is an alcohol by IR spectroscopy?


The product would have a broad absorption at ~3600 cm-1 in the IR spectrum

6. (8 points) A recently isolated microbial metabolite is found to have the empirical formula C4H7O and its mass

spectrum shows M+ = 142. Significant signals are seen in the IR spectrum at 1740 and 1650 cm-1. The 1H

NMR spectrum, collected in CDCl3, is given below. Provide a structure for the organic compound that

matches the data, and then match the protons in the molecule to the 1H NMR signals. (Klein Chapter 15)


1H NMR (ppm): 1.06 (d, 6H, J = 7.1 Hz), 1.36 (t, 3H, J = 7.0 Hz), 2.52 (octet, 1H, J = 7.1 Hz),

4.20 (q, 2H, J = 7.0 Hz), 5.83 (d, 1H, J = 16.0 Hz), 6.88 (dd, 1H, J = 7.1, 16.0 Hz)

5

7. (12 points) Provide a retrosynthetic plan for the molecule below that uses only the given starting materials as

sources of carbon. Then give a detailed synthesis of the compound that shows each product formed along the

way. You have access to all of the usual reagents in the lab (HBr, HNO3, NaBH4, Zn, Mg, etc.), as well as

techniques for separating isomers and byproducts (i.e. distillation, chromatography, etc.) as needed.


6

8. (20 points) Give the major organic product(s) expected from each step in the following reactions. You do

not have to show any mechanisms. (Klein Chapters 13 and 14)

1




1. (10 points) Give the expected major product(s) from the following nitration reaction, and then give a complete

mechanism for the conversion that includes resonance structures for the intermediate(s) formed. Explain why

you only get certain isomer(s) as the major product(s) in this reaction. (Klein Chapter 19)

2

2. (8 points) Give the structure of an unknown organic compound with the formula C7H14O2 and the following

spectral characteristics, and then match the 1H signals to your structure:

1H NMR (CDCl3): 0.90 (t, 3H, J = 7.0 Hz), 1.14 (d, 6H, J = 6.9 Hz), 1.73 (sextet, 2H, J = 7.0 Hz), 2.67 (septet, 1H, J = 6.9 Hz), 4.13 (t, 2H, J = 7.0 Hz)

13C NMR (CDCl3): 10.3 (q), 19.1 (q, double intensity), 21.9 (t), 34.0 (d), 66.5 (t), 177.0 (s)

(Klein Chapter 16)

3. (10 points) Provide the expected major product(s) from the following reaction, and then give a complete

mechanism for the process that includes any important resonance structures. (Klein Chapter 19)

3

4. (20 points) Give the major organic product(s) expected from each step in the following reaction sequences.

You do not have to show any mechanisms here. (Klein Chapters 17-19)

4

5. (12 points) Provide syntheses of the compounds below, starting from benzene, that show each product formed

along the way. You have access to all of the usual reagents in the lab (e.g. HNO3, Br2, NaOH, AlCl3, etc.), as

well as techniques for separating any isomers and byproducts as needed. (Klein Chapter 19)

6. (12 points) Give the products from each step of the following synthetic sequence and then, on the NMR axis

given below, draw the expected 1H spectrum of the final product. (Klein Chapters 13 and 16)

5

7. (12 points) Consider the following reaction and then answer the questions below related to the mechanism.

(Klein Chapter 17)

Draw a reaction profile (on the axes given below) that describes energy changes during the reaction.

Energy

In the space below, draw diagrams of all transition states and reactive intermediates (including resonance

structures), and indicate where they appear on the graph above. Indicate the rate-determining step, and

label that step as unimolecular or bimolecular. Finally, explain why the major product is formed here.

6

8. (10 points) Provide a retrosynthetic plan for the molecule shown that goes back only to the organic

compounds provided, and then show how you would build the molecule using chemistry seen in 3719 and

3720. (Klein Chapter 19)

9. (6 points) Indicate which of the following molecules are aromatic and explain your choices based on

applying Hückels’rule. (Klein Chapter 16)

1

Chemistry 3720 Practice Exam 2 Key Name:




1. (10 points) Give the expected major product(s) from the following nitration reaction, and then give a complete

mechanism for the conversion that includes resonance structures for the intermediate(s) formed. Explain

why you only get certain isomer(s) as the major product(s) in this reaction. (Klein Chapter 19)

2

2. (8 points) Give the structure of an unknown organic compound with the formula C7H14O2 and the following

spectral characteristics, and then match the 1H signals to your structure: (Klein Chapter 16)

1H NMR (CDCl3): 0.90 (t, 3H, J = 7.0 Hz), 1.14 (d, 6H, J = 6.9 Hz), 1.73 (sextet, 2H, J = 7.0 Hz), 2.67 (septet, 1H, J = 6.9 Hz), 4.13 (t, 2H, J = 7.0 Hz)

13C NMR (CDCl3): 10.3 (q), 19.1 (q, double intensity), 21.9 (t), 34.0 (d), 66.5 (t), 177.0 (s)

a = 0.90 (t, 3H, J = 7.0 Hz)

b = 1.73 (sextet, 2H, J = 7.0 Hz)

c = 4.13 (t, 2H, J = 7.0 Hz)

d = 1.14 (d, 6H, J = 6.9 Hz)

e = 2.67 (septet, 1H, J = 6.9 Hz)

3. (10 points) Provide the expected major product(s) from the following reaction, and then give a complete

mechanism for the process that includes any important resonance structures. (Klein Chapter 19)

3

4. (20 points) Give the major organic product(s) expected from each step in the following reaction sequences.

You do not have to show any mechanisms here. (Klein Chapters 17-19)

4

5. (12 points) Provide syntheses of the compounds below, starting from benzene, that show each product formed

along the way. You have access to all of the usual reagents in the lab (e.g. HNO3, Br2, NaOH, AlCl3, etc.), as

well as techniques for separating any isomers and byproducts as needed. (Klein Chapter 19)

6. (12 points) Give the products from each step of the following synthetic sequence and then, on the NMR axis

given below, draw the expected 1H spectrum of the final product. (Klein Chapters 13 and 16)

5

7. (12 points) Consider the following reaction and then answer the questions below related to the mechanism.

(Klein Chapter 17)

Draw a reaction profile (on the axes given below) that describes energy changes during the reaction.

In the space below, draw diagrams of all transition states and reactive intermediates (including resonance

structures), and indicate where they appear on the graph above. Indicate the rate-determining step, and

label that step as unimolecular or bimolecular. Finally, explain why the major product is formed here.

First step is R.D.S. and it is bimolecular (diene and HBr are involved); major product is the thermodynamic outcome since reaction is reversible at higher temperatures and more substituted alkene is favoured.

6

8. (8 points) Provide a retrosynthetic plan for the molecule shown that goes back only to the organic compounds

provided, and then show how you would build the molecule using chemistry seen in 3719 and 3720. (Klein

Chapter 19)

9. (6 pts) Indicate which of the following molecules are aromatic and explain your choices based on applying

Hückels’rule. (Klein Chapter 16)

1


complete the exam. Good Luck.

1. (8 points) Provide a complete mechanism, including all important resonance structures, for the following:

(Klein Chapter 22)

2


in the following reactions. You do not have to show any mechanisms. (Klein Chapters 20-22)

3

3. (14 points) Provide the major organic product from each step of the following synthetic sequence (in the boxes

provided). The spectroscopic clues along the way might help. (Klein Chapters 13-22)

4. (6 points) Number the following compounds in order of their decreasing reactivity with nucleophiles; 1 =

most reactive, 3 = least reactive. Then explain your reasoning. (Klein Chapter 21)

4

5. (8 points) Provide a complete mechanism that describes the following conversion. Include all resonance

structures for any intermediates that are formed. (Klein Chapter 21)

6. (8 points) Provide a complete mechanism for the following annulation that includes any important resonance

structures along the way. (Klein Chapter 22)

5

7. (8 points) Provide a retrosynthetic analysis for the following molecule that leads back only to 1-propanol as

the source of carbon. Then show an actual synthesis in the forward direction. (Klein Chapters 13-22)

8. (8 points) Provide a complete mechanism for the following ester saponification sequence: (Klein Chapter 21)

6

9. (20 points) Give the major organic product(s) expected from each step in the following reactions. You do not

have to show any mechanisms. (Klein Chapters 20-22)

1

Chemistry 3720 Practice Exam 3 - Key Name:


complete the exam. Good Luck.

1. (8 points) Provide a complete mechanism, including all important resonance structures, for the following:

(Klein Chapter 22)

Dieckmann Cyclization

2


in the following reactions. You do not have to show any mechanisms. (Klein Chapters 20-22)

3

3. (14 points) Provide the major organic product from each step of the following synthetic sequence (in the boxes

provided). The spectroscopic clues along the way might help. (Klein Chapters 13-22)

4. (6 points) Number the following compounds in order of their decreasing reactivity with nucleophiles; 1 =

most reactive, 3 = least reactive. Then explain your reasoning. (Klein Chapter 21)

4

5. (8 points) Provide a complete mechanism that describes the following conversion. Include all resonance

structures for any intermediates that are formed. (Klein Chapter 21)

6. (8 points) Provide a complete mechanism for the following annulation that includes any important resonance

structures along the way. (Klein Chapter 22)

Michael/Robinson sequence

5

7. (8 points) Provide a retrosynthetic analysis for the following molecule that leads back only to 1-propanol as

the source of carbon. Then show an actual synthesis in the forward direction. (Klein Chapters 13-22)

8. (8 points) Provide a complete mechanism for the following ester saponification sequence: (Klein Chapter 21)

Saponification

6

9. (20 points) Give the major organic product(s) expected from each step in the following reactions. You do not

have to show any mechanisms. (Klein Chapters 20-22)

1

Chemistry 3720, Spring 2014 Exam 1 Student Name: “Y” Number:


complete the exam. The spectroscopy sheet is attached at the back of the exam. Good Luck!

1. (8 points) Give a detailed explanation for the different regiochemical outcomes in the following two epoxide-

opening reactions.

2

2. (20 points) Provide the expected major products from each step of the following reaction sequences. Be sure

to include any stereochemical changes where applicable.

3

3. (9 points) Give the product expected under the following conditions. Then draw a complete mechanism for

the conversion being careful with the overall sequence of events as the ether is converted to the product.

4. (9 points) For the following conversion, provide a complete mechanism that describes all of the major events

on the way from starting material to product.

4

5. (16 points) In the boxes below, provide the product from each step of the following sequence. Using the

spectroscopic and molecular formula clues might help you come up with answers.



5

7. (6 points) Give the expected product from each of the following oxidation reactions, and then provide a brief

explanation for why each alcohol gives a different result.

8. (8 points) Which of the following molecules does the IR spectrum below match? Explain your choice here

by pointing out important signals that helped you to decide (Use the spectroscopy sheet for numbers).

6

9. (8 points) From the molecules shown below, choose which one matches the following mass spectrum. Then

explain your choice, including reasons for why you didn’t pick the other possible answers. Atomic masses (in

atomic mass units, a.m.u.) are as follows: C = 12 ; H = 1 ; Cl = 35.45 ; Br = 79.90.

10. (8 points) Provide a retrosynthesis for the following ether that goes back to the sources of carbon shown. Then

show how you would make the target molecule using any of the reactions seen so far in Chemistry 3719/

3720. Include a product from each of your synthetic steps.

1

Chemistry 3720, Spring 2014 Exam 1 - Key Student Name: “Y” Number:



1. (8 points) Give a detailed explanation for the different regiochemical outcomes in the following two epoxide-

opening reactions.

2



3

3. (9 points) Give the product expected under the following conditions. Then draw a complete mechanism for

the conversion being careful with the overall sequence of events as the ether is converted to the product.

The ether features a primary benzylic and phenolic oxygen. The HBr will

protonate the oxygen to make it a better leaving group and the bromide

anion will attack at the primary/benzylic carbon to give the benzylic

bromide. The phenolic OH will not react despite the excess HBr.

4. (9 points) For the following conversion, provide a complete mechanism that describes all of the major events

on the way from starting material to product.

4





5

7. (6 points) Give the expected product from each of the following oxidation reactions, and then provide a brief

explanation for why each alcohol gives a different result.

8. (8 points) Which of the following molecules does the IR spectrum below match? Explain your choice here

by pointing out important signals that helped you to decide (Use the spectroscopy sheet for numbers).

Each of the options contains C-C and C-H single bonds to sp3 carbons so those

signals would not be useful here. The absorbances highlighted help solve the

problem: the broad signal at ~3340 cm-1 corresponds to an alcohol group, which

precludes options b), c), and e). The absorbance at 1660 cm-1 corresponds to a

C=C group, which d) has but a) does not. The signal at 1030 would fit both a) and

d), however the absorbance at 900 cm-1, for sp2 =CH2, would only fit a terminal

olefin, i.e. option d).

6



atomic mass units, a.m.u.) are as follows: C = 12 ; H = 1 ; Cl = 35.45 ; Br = 79.90.

By simply adding up the atomic masses in each molecule, the answer is quickly revealed as being

chlorobenzene, b). The M+ signals at 112 and 114 a.m.u. match only this compound and reveal the

natural abundance isotopic ratio of Cl35 and Cl37. While each of these different compounds might

reasonably be expected to exhibit the 77 a.m.u. fragment, which corresponds to the phenyl radical

cation, only chlorobenzene would have the correct mass and two M+ signals in this (75:25) ratio.




1




HDI/Unsaturation Number = [#C atoms – ½#H atoms – ½#Halogen atoms + ½#N atoms] + 1

1. (8 points) Provide a detailed mechanism for the following reaction that includes all resonance structures for

any intermediate(s) that is/are formed. Which mechanism is this and which step is rate-determining?

2


to include any stereochemical information where applicable.

3

3. (15 points) An unknown organic compound is found to have the molecular formula C12H15BrO and the

following spectral data. Draw the expected structure of the unknown and match the 1H NMR and IR signals

to your molecule. IR : 1720, 1200, 800, 690 cm-1

1H NMR (CDCl3): 1.16 (d, 6H, J = 6.9 Hz), 3.05 (t, 2H, J = 7.0 Hz), 3.20 (septet, 1H, J = 6.9 Hz), 3.63 (t, 2H, J = 7.0 Hz),

7.32 (t, 1H, J = 6.8 Hz), 7.39 (d, 1H, J = 6.8 Hz), 7.79 (s, 1H), 7.93 (d, 1H, J = 6.8 Hz)

13C NMR (CDCl3): 18.1 (q, double intensity), 31.6 (t), 35.1 (d), 39.0 (t), 126.0 (d), 127.7 (d), 128.5 (d),

132.1 (d), 136.6 (s), 139.3 (s), 202.1 (s)

4

3. (9 points) Give the major product expected under the following conditions. Then draw a complete mechanism

for the conversion that includes important resonance structures for any intermediate(s).

4. (9 points) Indicate whether each of the following molecules is expected to be aromatic or not aromatic and

then draw Frost Circles of molecular orbitals for each system to back up your answers.

5



6. (8 points) In the addition of HBr to 1,3-butadiene, the product distribution depends greatly on the temperature

at which the reaction is run. Give a mechanism for this process and explain the expected outcomes at low

temperature and high temperature.

6

7. (9 points) A new antibiotic compound is thought to have one of the structures shown below. From the spectral

data, which structure corresponds to the drug? Match the proton NMR data to your answer.

UV : 290 nm M+ = 205 a.m.u. IR : 1720, 1640, 1200, 800 cm-1

1H NMR : 1.08 (t, 3H, J = 7.0 Hz), 2.98 (q, 2H, J = 7.0 Hz), 6.54 (d, 1H, J = 12.0 Hz),

7.91 (d, 1H, J = 12.0 Hz), 8.03 (d, 2H, J = 6.8 Hz), 8.37 (d, 2H, J = 6.8 Hz).

13C NMR : 7.9 (q), 34.0 (t), 123.8 (double intensity, d), 126.2 (d), 129.0 (double intensity, d),

141.3 (s), 142.8 (d), 147.1 (s), 200.4 (s).

8. (8 points) Give the major product(s) expected under the following conditions. Then provide a complete

mechanism for the conversion that includes important resonance structures for any intermediate(s). Briefly

explain the regiochemical outcome of the reaction.

1





1. (8 points) Provide a detailed mechanism for the following reaction that includes all resonance structures for

any intermediate(s) that is/are formed. Which mechanism is this and which step is rate-determining?

2



3

3. (15 points) An unknown organic compound is found to have the molecular formula C12H15BrO and the

following spectral data. Draw the expected structure of the unknown and match the 1H NMR and IR signals

to your molecule. IR : 1720, 1200, 800, 690 cm-1

1H NMR (CDCl3): 1.16 (d, 6H, J = 6.9 Hz), 3.05 (t, 2H, J = 7.0 Hz), 3.20 (septet, 1H, J = 6.9 Hz), 3.63 (t, 2H, J = 7.0 Hz),

7.32 (t, 1H, J = 6.8 Hz), 7.39 (d, 1H, J = 6.8 Hz), 7.79 (s, 1H), 7.93 (d, 1H, J = 6.8 Hz)

13C NMR (CDCl3): 18.1 (q, double intensity), 31.6 (t), 35.1 (d), 39.0 (t), 126.0 (d), 127.7 (d), 128.5 (d),

132.1 (d), 136.6 (s), 139.3 (s), 202.1 (s)

4

4. (9 points) Give the major product expected under the following conditions. Then draw a complete mechanism

for the conversion that includes important resonance structures for any intermediate(s).

5. (9 points) Indicate whether each of the following molecules is expected to be aromatic or not aromatic and

then draw Frost Circles of molecular orbitals for each system to back up your answers.

5



7. (8 points) In the addition of HBr to 1,3-butadiene, the product distribution depends greatly on the temperature

at which the reaction is run. Give a mechanism for this process and explain the expected outcomes at low

temperature and high temperature.

6

8. (9 points) A new antibiotic compound is thought to have one of the structures shown below. From the spectral

data, which structure corresponds to the drug? Match the proton NMR data to your answer.

UV : 290 nm M+ = 205 a.m.u. IR : 1720, 1640, 1200, 800 cm-1

1H NMR : 1.08 (t, 3H, J = 7.0 Hz), 2.98 (q, 2H, J = 7.0 Hz), 6.54 (d, 1H, J = 12.0 Hz),

7.91 (d, 1H, J = 12.0 Hz), 8.03 (d, 2H, J = 6.8 Hz), 8.37 (d, 2H, J = 6.8 Hz).

13C NMR : 7.9 (q), 34.0 (t), 123.8 (double intensity, d), 126.2 (d), 129.0 (double intensity, d),

141.3 (s), 142.8 (d), 147.1 (s), 200.4 (s).

9. (8 points) Give the major product(s) expected under the following conditions. Then provide a complete

mechanism for the conversion that includes important resonance structures for any intermediate(s). Briefly

explain the regiochemical outcome of the reaction.

Having the Br go in the meta position avoids positive charge developing next to the

highly electron-withdrawing CF3 group in the intermediate.

1





1. (8 points) Provide a detailed mechanism for the following reaction sequence that includes resonance structures

for any intermediate(s) that is/are formed.

2



3

3. (10 points) Design a retrosynthesis for the following molecule that goes back to the starting materials shown.

Then give the synthesis in the forward direction assuming that you have access to any of the reagents seen in

Chemistry 3719 and 3720.

4. (8 points) Give the major product expected to be formed under the following conditions, and then draw a

mechanism for the conversion that includes important resonance structures for any intermediate(s).

4

5. (8 points) Provide the major product expected from the following reaction and then a detailed mechanism

that includes all important resonance structures for any intermediates that are formed.


spectroscopic and nomenclature clues might help you come up with answers.

5

7. (10 points) Provide a detailed mechanism for the following Wolf-Kischner reduction sequence. Include all of

the resonance structures for any intermediates that are formed.

8. (8 points) Methyl benzoate, benzoyl chloride and benzamide are all derivatives of benzoic acid with quite

differing reactivity towards nucleophiles. Draw structures for each of the molecules, then indicate which is

the most reactive and which is the least reactive in reactions with nucleophiles. Explain your choices.

6

9. (6 points) For each of the following molecules, identify any alpha protons and then draw all of the possible

enolates that would be formed when each molecule was reacted with a strong base.

10. (8 points) Give a detailed mechanistic interpretation for the following conversion. Be sure to show all of the

resonance structures for any intermediates that are formed.

1





1. (8 points) Provide a detailed mechanism for the following reaction sequence that includes resonance structures

for any intermediate(s) that is/are formed.

2



3

3. (10 points) Design a retrosynthesis for the following molecule that goes back to the starting materials shown.

Then give the synthesis in the forward direction assuming that you have access to any of the reagents seen in

Chemistry 3719 and 3720.

4. (8 points) Give the major product expected to be formed under the following conditions, and then draw a

mechanism for the conversion that includes important resonance structures for any intermediate(s).

4


that includes all important resonance structures for any intermediates that are formed.


spectroscopic and nomenclature clues might help you come up with answers.

5

7. (10 points) Provide a detailed mechanism for the following Wolf-Kischner reduction sequence. Include all of

the resonance structures for any intermediates that are formed.

8. (8 points) Methyl benzoate, benzoyl chloride and benzamide are all derivatives of benzoic acid with quite

differing reactivity towards nucleophiles. Draw structures for each of the molecules, then indicate which is

the most reactive and which is the least reactive in reactions with nucleophiles. Explain your choices.

Benzoyl chloride is the most reactive whereas benzamide is the least reactive. The former is not

stabilized much by lone pair donation from the large Cl whereas benzamide will benefit from

donation by the NH2 group. Also, Cl is a much better leaving group than NH2.

6

9. (6 points) For each of the following molecules, identify any alpha protons and then draw all of the possible

enolates that would be formed when each molecule was reacted with a strong base.

10. (8 points) Give a detailed mechanistic interpretation for the following conversion. Be sure to show all of the


1

Chemistry 3720, Spring 2014 Final Exam Student Name: “Y” Number:


complete the exam. The spectroscopy sheet is attached as the last page. Good Luck!


1. (8 points) Provide the products that will be formed under the following reaction conditions and then a detailed

mechanism for the conversion.

2



3

3. (15 points) An unknown organic compound is found to have the molecular formula C9H16O2 and the following

spectral data. Draw the expected structure of the unknown and match the 1H NMR and IR signals to your

molecule. IR : 3000, 1730, 1620, 1200 cm-1.

1H NMR (CDCl3): 1.05 (s, 9H), 1.21 (t, 3H, J = 7.0 Hz), 4.06 (q, 2H, J = 7.0 Hz),

5.85 (d, 1H, J = 16.0 Hz), 6.88 (d, 1H, J = 16.0 Hz)

13C NMR (CDCl3): 14.2 (q), 29.5 (s, triple intensity), 32.9 (s), 61.4 (t), 115.2 (d), 155.4 (d), 166.5 (s)

4

4. (10 points) Design a retrosynthesis for the following molecule from the starting materials shown, then a

synthesis in the forward direction assuming that you have any of the reagents seen in Chemistry 3719/3720.

5. (10 points) Provide a detailed mechanism for the following synthetic conversion that includes all resonance

structures for any intermediate(s) that is/are formed. Use “R” groups to abbreviate structures.

5


that includes all resonance structures for any intermediates that are formed. Why are no other isomers formed?


spectroscopic and molecular formula clues might help you to come up with answers.

6

8. (10 points) Within the following polymers, identify the repeating units and then suggest starting materials that

could be used for their synthesis. Do you expect the polymers to react with water at neutral pH? Why?

9. (10 points) Give a detailed mechanism for the following conversion (from a total synthesis of the natural

product Hirsutene) that includes all resonance structures for any intermediates that are formed.

7

10. (10 points) Draw a detailed mechanism for the following Gabriel amine synthesis that includes all important

resonance structures for intermediates that are formed.

11. (10 points) Provide a mechanistic interpretation for the following disaccharide hydrolysis. Be sure to show all

of the resonance structures for any intermediates that are formed. Explain the “squiggles” used here, and label

any carbons in the starting material and products that will react with NaBH4 in methanol.

8

12. (30 points) For the following multi-step reaction sequence, give mechanisms for the formation of the products

from each step, including resonance structures where appropriate. Use the back of the page if needed.

9

13. (10 points) Circle which one of the four isomeric compounds below would have the spectral data given, and

then match the IR and proton data to your structure. IR : 3000, 1710, 1200, 760, 680 cm-1.

1H NMR (ppm): 1.16 (d, 6H, J = 7.0 Hz), 3.20 (septet, 1H, J = 7.0 Hz), 3.77 (s, 3H), 7.12 (d, 1H, J = 6.9 Hz),

7.43 (s, 1H), 7.61 (t, 1H, J = 6.9 Hz), 7.71 (d, 1H, J = 6.9 Hz)

13C NMR (ppm): 18.1 (q, double intensity), 35.1 (d), 55.8 (q), 118.7 (d), 121.1 (d) 122.1 (d),

129.3 (d), 137.7 (s), 160.6 (s), 202.1 (s)

14. (15 points) Show a detailed mechanism for the following Michael addition – aldol condensation sequence that

includes all of the resonance structures for intermediates that are formed.

10



1




1. (8 points) Provide the product(s) expected from each step of the following reaction sequence as well as

detailed mechanisms for each step in the conversion of starting materials to product(s).

2



3

3. (9 points) Give the products expected to be formed from each step under the following conditions. Then draw

complete mechanisms for each of the conversions.



atomic mass units, a.m.u.) are as follows: C = 12 ; H = 1 ; O = 16 ; F = 19 ; Cl = 35.45 ; Br = 79.90.

4

5. (14 points) In the boxes below, provide the product(s) from each step of the following sequence. Using the


6. (8 points) Give the major product(s) expected to be formed under the following conditions as well as a

complete mechanism for its/their formation.

5

7. (8 points) Give the expected product(s) from each step of the following reaction sequence, and then provide

a mechanism for each synthetic step.




6

9. (9 points) Which of the following molecules does the IR spectrum below match? Explain your choice here by

pointing out important signals that helped you to decide on your choice and why the spectrum does not match

the other possibilities (Use the spectroscopy sheet for numbers).

10. (8 points) For the following multi-step synthesis, give the product expected from each step as well as complete

mechanisms that describe all of the major events on the way from starting material to the final product.

1





detailed mechanisms for each step in the conversion of starting materials to product(s).

2



3

3. (9 points) Give the products expected to be formed from each step under the following conditions. Then draw

complete mechanisms for each of the conversions.



atomic mass units, a.m.u.) are as follows: C = 12 ; H = 1 ; F = 19 ; Cl = 35.45 ; Br = 79.90.

Each of the four possible answers would give the same base peak at m/z = 92 by losing the X

atom/group from the methylbenzene ring, however only the bromo derivative would have M and

M+2 signals due to the two naturally occurring isotopes of bromine. The approximately equal

intensity of the two signals at 170 and 172 confirm this.

4

5. (14 points) In the boxes below, provide the product(s) from each step of the following sequence. Using the


6. (8 points) Give the expected major product(s) expected to be formed under the following conditions as well

as a complete mechanism for its/their formation.

The benzene ring will not undergo substitution since SN1 and SN2 reactions do not occur at sp2 C.

5

7. (8 points) Give the expected product(s) from each step of the following reaction sequence, and then provide

a mechanism for each synthetic step.




6

9. (9 points) Which of the following molecules does the IR spectrum below match? Explain your choice here by

pointing out important signals that helped you to decide on your choice and why the spectrum does not match

the other possibilities (Use the spectroscopy sheet for numbers).

The strong, broad signal at ~3300 cm-1 indicates an OH group, most likely in an alcohol. The carboxylic

acid would have a C=O signal around ~1750, which is absent here; the ether would not have the strong

OH signal at ~3300 ; the ketone would show a strong C=O signal at ~1730, which is absent here.

10. (8 points) For the following multi-step synthesis, give the product expected from each step as well as complete

mechanisms that describe all of the major events on the way from starting material to the final product.

1





1. (9 points) Provide the product(s) from each step of this reaction sequence as well as detailed mechanisms for

each step in the conversion of starting materials to product. Then draw the 1H NMR of the product.

2



3

3. (9 points) Using Hűckel’s rule and Frost circles, indicate which of the following molecules will be aromatic

and which will be anti-aromatic. Include the Hűckel calculation in each of your answers.

4. (9 points) Which one of the following compounds matches the spectral data given below? Your answer should

include reasoning for why you picked that compound and not the others.

1H NMR (CDCl3) ppm: 1.05 (s, 9H), 5.83 (d, 1H, J = 16 Hz), 6.71 (d, 1H, J = 16 Hz), 7.31-7.44

(m, 5H).

13C NMR (CDCl3) ppm: 29.5 (q, triple intensity), 32.9 (s), 114.5 (d), 121.6 (d, double intensity),

125.5 (d), 129.1 (d, double intensity), 151.3 (s), 158.2 (d), 164.3 (s).

4

5. (14 points) In the boxes below, provide the major product from each step of the following sequence. Using

the spectroscopic and molecular formula clues might help you to come up with answers.

6. (8 points) Give the major and minor product expected to be formed under the following conditions as well as

a complete mechanism for their formation. Explain the major/minor distribution at this reaction temperature.

5

7. (14 points) An unknown organic compound has the molecular formula C13H18O2; the mass spectrum shows

M+ = 206 a.m.u., the IR spectrum shows significant signals at 1720, 1200, and 800 cm-1, and the 1H and 13C

NMR spectra are given below. Suggest a structure for the unknown molecule that matches the data and then

indicate which signals belong to which protons in the 1H NMR spectrum.

1H NMR (CDCl3) ppm : 0.98 (t, 3H, J = 7.1 Hz), 1.29 (d, 6H, J = 7.0 Hz), 1.51 (sextet, 2H, J = 7.1 Hz), 2.96 (t,

2H, J = 7.1 Hz), 4.69 (septet, 1H, J = 7.0 Hz), 7.01 (d, 2H, J = 7.5 Hz), 7.92 (d, 2H, J = 7.5 Hz).

13C NMR (CDCl3) ppm : 13.6 (q), 17.4 (t), 22.0 (q, double intensity), 40.4 (t), 75.8 (d), 114.3 (d, double

intensity), 129.4 (d, double intensity), 130.8 (s), 161.8 (s), 200.1 (s)

6

8. (9 points) Provide a detailed mechanism for the following transformation that includes all important resonance

structures for the intermediate involved. Then explain, briefly, the observed regioselectivity.

9. (8 points) Which of the following diene compounds do you expect to participate in Diels-Alder reactions and

which will not? Explain your choices.

1






detailed mechanisms for each step in the conversion of starting materials to product.

2



3

3. (9 points) Using Hűckel’s rule and Frost circles, indicate which of the following molecules will be aromatic

and which will be anti-aromatic. Include the Hűckel calculation in each of your answers.

4. (9 points) Which one of the following compounds matches the spectral data given below? Your answer should

include reasoning for why you picked that compound and not the others.

1H NMR (CDCl3) ppm: 1.05 (s, 9H), 5.83 (d, 1H, J = 16 Hz), 6.71 (d, 1H, J = 16 Hz), 7.31-7.44

(m, 5H).

13C NMR (CDCl3) ppm: 29.5 (q, triple intensity), 32.9 (s), 114.5 (d), 121.6 (d, double intensity),

125.5 (d), 129.1 (d, double intensity), 151.3 (s), 158.2 (d), 164.3 (s).

13C signal at 164.3 indicates an ester so compounds a, c, and d don’t fit. Compound f would have three 1H

signals for the alkene; the J value of 16 Hz indicates the trans alkene in compound e and not cis in b.

4



6. (8 points) Give the major and minor product expected to be formed under the following conditions as well as

a complete mechanism for their formation. Explain the major/minor distribution at this reaction temperature.

5


M+ = 206 a.m.u., the IR spectrum shows significant signals at 1720, 1200, and 800 cm-1, and the 1H and 13C

NMR spectra are given below. Suggest a structure for the unknown molecule that matches the data and then

indicate which signals belong to which protons in the 1H NMR spectrum.

1H NMR (CDCl3) ppm : 0.98 (t, 3H, J = 7.1 Hz), 1.29 (d, 6H, J = 7.0 Hz), 1.51 (sextet, 2H, J = 7.1 Hz), 2.96 (t,

2H, J = 7.1 Hz), 4.69 (septet, 1H, J = 7.0 Hz), 7.01 (d, 2H, J = 7.5 Hz), 7.92 (d, 2H, J = 7.5 Hz).

13C NMR (CDCl3) ppm : 13.6 (q), 17.4 (t), 22.0 (q, double intensity), 40.4 (t), 75.8 (d), 114.3 (d, double

intensity), 129.4 (d, double intensity), 130.8 (s), 161.8 (s), 200.1 (s)

6

8. (9 points) Provide a detailed mechanism for the following transformation that includes all important resonance

structures for the intermediate involved. Then explain, briefly, the observed regioselectivity.

9. (8 points) Which of the following diene compounds do you expect to participate in Diels-Alder reactions and

which will not? Explain your choices.

1





1. (8 points) Provide a complete mechanism for the following conversion that includes resonance structures for

any intermediates that are formed. What experimental measures would you take to push this reaction

completely to product?

2

2. (9 points) Starting with benzene, provide a synthesis of methyl 3-aminobenzoate using any of the chemistry

and reagents seen thus far in 3719 and 3720. Show the major product from each step; however you do not

need to show a retrosynthesis unless it helps you to develop the synthetic route.

3. (10 points) Draw a complete mechanism for the following sequence that includes all resonance structures for

any intermediates that are formed along the reaction profile.

3



4



6. (7 points) Provide a complete mechanism for the following transformation that includes all resonance

structures for the intermediate that is formed.

5

7. (8 points) Give a complete mechanism for the following nitrile hydrolysis that includes all important


8. (8 points) By using curved arrows, show how the following aldol transformation occurs. Draw all important

resonance structures where applicable.

6

9. (8 points) Draw a complete mechanism for the following alpha-bromination reaction that includes all

resonance structures for any intermediates that formed along the way from starting material to product.

10. (8 points) Give the structure of the major product expected from each step in the following synthetic

sequence. No need to show mechanisms here.

1





1. (8 points) Provide a complete mechanism for the following conversion that includes resonance structures for

any intermediates that are formed. What experimental measures would you take to push this reaction

completely to product?

Use a drying agent like anhydrous MgSO4 to remove the water and push the equilibrium to product.

2

2. (9 points) Starting with benzene, provide a synthesis of methyl 3-aminobenzoate using any of the chemistry

and reagents seen thus far in 3719 and 3720. Show the major product from each step; however you do not

need to show a retrosynthesis unless it helps you to develop the synthetic route.

3. (10 points) Draw a complete mechanism for the following sequence that includes all resonance structures for

any intermediates that are formed along the reaction profile.

3



4



6. (7 points) Provide a complete mechanism for the following transformation that includes all resonance

structures for the intermediate that is formed.

5

7. (8 points) Give a complete mechanism for the following nitrile hydrolysis that includes all important


8. (8 points) By using curved arrows, show how the following aldol transformation occurs. Draw all important

resonance structures where applicable.

6

9. (8 points) Draw a complete mechanism for the following alpha-bromination reaction that includes all

resonance structures for any intermediates that formed along the way from starting material to product.

10. (8 points) Give the structure of the major product expected from each step in the following synthetic

sequence. No need to show mechanisms here.

1

Chemistry 3720, Spring 2015 Final Exam Student Name: “Y” Number:


complete the exam. The spectroscopy sheet is attached as the last page. Good Luck!


1. (8 points) For the following Wittig reaction sequence, give the products expected from each step and then a

complete mechanism for the conversion of the alkyl halide into the final product.

2

2. (8 points) A new medicinal compound, isolated from a tropical plant, has one of the following structures.

Using the provided spectral data, indicate which structure is correct and then explain your decision by

matching the data to the structure.

Selected data: IR : 3350, 3000, 1690 cm-1 ; 13C NMR : 170, 150, 120 ppm ; 1H NMR : 6.0 ppm (s, 1H)

3. (8 points) In the following reaction one major product is formed with molecular formula C7H5N3O6. The

molecule has 5 signals in its 13C NMR spectrum and 2 signals in the 1H NMR. Draw the product; give a

mechanism for the first nitration, and finally a brief explanation for the observed regioselectivity.

3

4. (8 points) Provide a detailed mechanism for the following prostaglandin synthesis that includes all important

resonance structures for intermediates that are formed. Use “R” groups for brevity where possible.

5. (8 points) Draw a detailed mechanism for the following ester conversion that includes all important resonance

structures for any intermediates that are formed.

4


to take tautomerism into consideration where applicable.

5



6. (8 points) Provide a complete mechanism for the following transformation that explains how the two regio-

isomeric products are formed.

6

7. (9 points) Starting with benzene, provide an efficient synthesis of 4-nitrobenzoic acid that employs any of the

chemistry seen throughout Chemistry 3719 and 3720. Provide the product from each step.

8. (10 points) Give a retrosynthesis for this molecule that goes back to cyclohexanol and ethanol as the only

sources of carbon. Then build the molecule in the forward direction showing the product from each step.

7

9. (8 points) Draw Frost circles and apply Hückel’s rule to decide if each of the following molecules is aromatic

or not. You need to show the results of your Hückel calculations for full credit.

10. (8 points) Draw the structure of the monomer precursor that would be needed to produce each of the four

polymers below. Label each polymer as being either the “addition” or “condensation” type.

8

11. (8 points) Draw a complete mechanism for the following cyclization process that includes all resonance

structures for any intermediates that formed along the way from starting material to product. Use “R” groups

to abbreviate structures as appropriate.

12. (8 points) Give the structure of the major product expected from each step in the following synthetic sequence

as well as detailed mechanisms for their formation.

9


M+ = 178.10 a.m.u., the IR spectrum shows significant signals at 1740, 1050, 760 and 690 cm-1, and the 1H

and 13C NMR spectra are given below. Suggest a structure for the unknown molecule that matches the data

and then indicate which signals belong to which protons in the 1H NMR spectrum.

1H NMR (CDCl3) ppm : 1.20 (d, 6H, J = 7.1 Hz), 2.87 (septet, 1H, J = 7.1 Hz), 3.89 (singlet, 3H), 7.35 (t, 1H, J

= 7.5 Hz), 7.49 (d, 1H, J = 7.5 Hz), 7.89 (d, 1H, J = 7.5 Hz), 7.99 (s, 1H).

13C NMR (CDCl3) ppm : 23.3 (q, double intensity), 33.2 (d), 51.5 (q), 127.1 (d), 127.2 (d),

128.3 (d), 129.8 (s), 130.4 (d), 150.0 (s), 165.9 (s)

10

14. (7 points) Provide a complete mechanism for the following Baeyer-Villiger oxidation. Then try to explain the

regioselectivity observed in this reaction.

15. (7 points) Give a detailed mechanism for the following reductive amination reaction that includes resonance


16. (7 points) Draw a detailed mechanism for the following cyclization reaction that includes resonance structures

for any intermediates that are formed.

11

17. (8 points) Provide a complete mechanism for the following “iodoform” reaction that includes all resonance


18. (8 points) Give the expected products for the two epoxide reactions shown below as well as mechanisms for

their formation that include any important resonance structures. How do your mechanisms explain the

observed optical rotation data?

12

19. (8 points) For the following Robinson annulation, provide a detailed step-by-step mechanism that explains

the formation of the third cycle. Include resonance structures where relevant.

20. (8 points) The following molecule is a pentasaccharide that induces antibodies to epithelial cancer cells when

conjugated to various proteins. When this molecule is treated with H+/H2O it is hydrolyzed to the five

individual monosaccharides by cleavage of each of the acetal linkages. Circle each acetal carbon in the

pentasaccharide and then draw the five reducing sugars expected to be formed after acetal hydrolysis.

Documents

OChem2 Old Exams 3. (16 points) Give the expected major product from each step of the following reaction sequence. No need to show any mechanisms. (Klein Chapter 13) 4. (9 points)