Chemistry 3720 Old Exams. Practice Exams & Keys

Transcription

1 Chemistry 3720 ld Exams Practice Exams & Keys

2 Spring 2017 Page File 3 Spring 2017 Exam 1 10 Spring 2017 Exam 1 Key 16 Spring 2017 Exam 2 23 Spring 2017 Exam 2 Key 29 Spring 2017 Exam 3 36 Spring 2017 Exam 3 Key 42 Spring 2017 Final (No Key)

3 Chemistry 3720, Spring 2017 Exam 1 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! 1. (8 pts) Give a retrosynthetic plan for building the following molecule from the sources of carbon shown. Then show your synthesis in the forward direction that would result in the alkyl bromide. You may assume that you have access to all of the usual reagents in an organic lab. 1

4 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any stereochemical changes where applicable. 2

5 3. (8 pts) The mass spectrum below belongs to one of the five compounds shown. Indicate which molecule matches the spectrum and explain why you chose that one and not the other four. Atomic masses (in atomic mass units, a.m.u.) are as follows: C = 12 ; H = 1 ; = 16 ; F = 19 ; Cl = ; Br = (8 pts) Draw a complete mechanism for the following ester to ether conversion. 3

6 5. (9 pts) For each of the following reactions, label the oxidation state of the highlighted carbon atoms in the starting material and product. Then indicate whether the reaction is an oxidation, reduction or neither, and give a reagent (above the arrow) that will accomplish the conversion. 6. (7 pts) IR spectrum A belongs to a starting material and B belongs to the product when A is reacted under certain conditions. f the reactions shown, which one matches the IR data give? Explain your choice. 4

7 7. (16 pts) In the boxes below, give the major product(s) from each step of the following sequence. The given clues might help you to work out the answers. If no reaction is expected, write NR in the box. 8. (8 pts) For each of the following epoxide ring-opening reactions, explain in some detail the regioselectivity and stereoselectivity observed. Discuss the different mechanisms operating. 5

8 9. (8 pts) The following attempted synthesis contains a fatal flaw that prevents it from actually working. What is wrong here and how would you make it work? Show the steps and reagents required for your synthesis. 10. (8 pts) For each of the following molecules, indicate how many different signals you expect to see in the proton ( 1 H) NMR spectrum. Then label the approximate chemical shift (ppm) for the highlighted atoms. 6

9 Youngstown State University rganic Chemistry Spectral Data Sheet Approximate 1 H NMR Chemical Shifts (parts per million) R 3 C-H (alkyl) 0.9 to 1.8 R 3 N-C-H (N neighbor) 2.2 to 2.9 C=C-C-H (allylic) 1.6 to 2.6 Cl-C-H (Cl neighbor) 3.1 to 4.1 =C-C-H (alpha to C=) 2.1 to 2.5 Br-C-H (Br neighbor) 2.7 to 4.1 NC-C-H (alpha to CN) 2.1 to C-H ( neighbor) 3.3 to 3.7 C C H (alkyne) 2.5 R 2 N-H (amine) 1 to 3 Ar-C-H (benzylic) 2.3 to 2.8 R-H (alcohol) 0.5 to 5 C=C-H (alkene) 4.5 to 6.5 Ar--H (phenol) 6 to 8 Ar-H (benzene) 6.5 to 8.5 -C 2 H (carboxylic acid) 10 to 13 =C-H (aldehyde) 9 to 10 Approximate 13 C NMR Chemical Shifts (parts per million) RCH 3 (alkyl) 0 to 35 RCH 2 Br (alkyl bromide) 20 to 40 R 2 CH 2 (alkyl) 15 to 40 RCH 2 Cl (alkyl chloride) 25 to 50 R 3 CH (alkyl) 25 to 50 RCH 2 NH 2 (alkyl amine) 35 to 50 R 4 C (alkyl) 30 to 40 RCH 2 R (alcohol or ether) 50 to 65 R-CC-R (alkyne) 65 to 90 RCN (nitrile) 110 to 125 R 2 C=CR 2 (alkene) 100 to 150 RC 2 R (acid, ester) 160 to 185 Benzene C (aromatic) 110 to 175 RCH, R 2 C (ald hyde, ketone) 190 to 220 Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) 3200 to 3600 C=C (alkenes) 1620 to H (carbox. acid) 2500 to 3600 C= (ald., ketones) 1710 to 1750 R 2 N-H (amine) 3350 to 3500 C= (acyl halides) 1770 to 1815 sp C-H (alkynes) 3310 to 3320 C= (esters) 1730 to 1750 sp 2 C-H (alkenes) 3000 to 3100 C= (amides) 1680 to 1700 sp 3 C-H (alkanes) 2850 to 2950 sp 2 C- (carbonyls) 1200 triple bond (alkynes) 2100 to 2200 sp 3 C- (alcoh., ethers) 1025 to 1200 triple bond (nitriles) 2240 to 2280 Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstit d benzene 730 to 770, 690 to 710 R 2 C=CH 2 (alkenes) 890 ortho-disubstit d benzene 735 to 770 R 2 C=CHR (alkenes) 790 to 840 meta-disubstit d benzene 750 to 810, 680 to 730 para-disubstituted benzene 790 to 840

10 Chemistry 3720, Spring 2017 Exam 1 Key Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! 1. (8 pts) Give a retrosynthetic plan for building the following molecule from the sources of carbon shown. Then show your synthesis in the forward direction that would result in the alkyl bromide. You may assume that you have access to all of the usual reagents in an organic lab. 1

11 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any stereochemical changes where applicable. 2

12 3. (8 pts) The mass spectrum below belongs to one of the five compounds shown. Indicate which molecule matches the spectrum and explain why you chose that one and not the other four. Atomic masses (in atomic mass units, a.m.u.) are as follows: C = 12 ; H = 1 ; = 16 ; F = 19 ; Cl = ; Br = (8 pts) Draw a complete mechanism for the following ester to ether conversion. 3

13 5. (9 pts) For each of the following reactions, label the oxidation state of the highlighted carbon atoms in the starting material and product. Then indicate whether the reaction is an oxidation, reduction or neither, and give a reagent (above the arrow) that will accomplish the conversion. 6. (7 pts) IR spectrum A belongs to a starting material and B belongs to the product when A is reacted under certain conditions. f the reactions shown, which one matches the IR data give? Explain your choice. 4

14 7. (16 pts) In the boxes below, give the major product(s) from each step of the following sequence. The given clues might help you to work out the answers. If no reaction is expected, write NR in the box. 8. (8 pts) For each of the following epoxide ring-opening reactions, explain in some detail the regioselectivity and stereoselectivity observed. Discuss the different mechanisms operating. 5

15 9. (8 pts) The following attempted synthesis contains a fatal flaw that prevents it from actually working. What is wrong here and how would you make it work? Show the steps and reagents required for your synthesis. 10. (8 pts) For each of the following molecules, indicate how many different signals you expect to see in the proton ( 1 H) NMR spectrum. Then label the approximate chemical shift (ppm) for the highlighted atoms. 6

16 Chemistry 3720, Spring 2017 Exam 2 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! #Pi bonds and/or Cycles = [#C - (#H/2) - (#X/2) + #N/2] (8 pts) Provide the major product(s) expected to be formed under the following conditions and then draw a detailed mechanism for the process that includes all important resonance structures where applicable. Why is there only one major product formed here? 1

17 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any regiochemical issues where applicable. 2

18 3. (9 pts) For each of the following molecules, draw a Frost circle and populate the molecular orbitals with the appropriate number of electrons. Then apply Hückel s rule to each system and indicate which molecule(s) is/are aromatic. Give a few words of explanation for your choices. 4. (8 pts) Draw the major final product expected from each of the following reactions: 3

19 5. (18 pts) A new anti-cancer compound has been isolated from a microorganism and is found, from the mass spectrum, to have the formula C 12 H 14 2 and M + of 190 atomic mass units. The infra-red spectrum has signals at 3500, 1740, 740 and 700 wavenumbers and the proton and carbon spectra are given below. Provide the structure of the unknown and then indicate which signals belong to which atoms in the 1 H NMR spectrum. 1 H NMR (ppm): 0.86 (d, 6H, J = 7.0 Hz); 2.38 (octet, 1H, J = 7.0 Hz); 5.63 (dd, 1H, J = 12.0, 7.0 Hz); 6.35 (d, 1H, J = 12.0 Hz); 7.55 (d, 2H, J = 8.0 Hz); 7.83 (d, 2H, J = 8.0 Hz); (s, 1H). 13 C NMR (ppm): 22.6 (q); 28.0 (d); (d); (d); (s); (d); (s); (d); (s). 4

20 6. (8 pts) Provide the major product that you expected to be formed under the following conditions. Then draw a complete mechanism, including all important resonance structures, for the product s formation. Explain, briefly, why this particular product is major. 7. (7 pts) The 13 C spectrum below belongs to one of the five molecules given. Indicate which one you think matches the NMR data and explain your choice by pointing out which signal matches which carbon(s) and how the coupling data helped inform your decision. 13 C NMR (ppm): 23.3 (q); 33.2 (d); (d); (d); (s); (s); (d). 5

21 8. (6 pts) Provide the major product that you would expect to be formed under each of the following reaction conditions. Then explain the outcomes by discussing the effect of temperature on the reaction pathway. 9. (16 pts) In the boxes provided, draw the expected major product from each step in the following synthetic scheme. Use the clues as needed and be careful if/when stereochemistry/regiochemistry is an issue. 6

22 Youngstown State University rganic Chemistry Spectral Data Sheet Approximate 1 H NMR Chemical Shifts (parts per million) R 3 C-H (alkyl) 0.9 to 1.8 R 3 N-C-H (N neighbor) 2.2 to 2.9 C=C-C-H (allylic) 1.6 to 2.6 Cl-C-H (Cl neighbor) 3.1 to 4.1 =C-C-H (alpha to C=) 2.1 to 2.5 Br-C-H (Br neighbor) 2.7 to 4.1 NC-C-H (alpha to CN) 2.1 to C-H ( neighbor) 3.3 to 3.7 C C H (alkyne) 2.5 R 2 N-H (amine) 1 to 3 Ar-C-H (benzylic) 2.3 to 2.8 R-H (alcohol) 0.5 to 5 C=C-H (alkene) 4.5 to 6.5 Ar--H (phenol) 6 to 8 Ar-H (benzene) 6.5 to 8.5 -C 2 H (carboxylic acid) 10 to 13 =C-H (aldehyde) 9 to 10 Approximate 13 C NMR Chemical Shifts (parts per million) RCH 3 (alkyl) 0 to 35 RCH 2 Br (alkyl bromide) 20 to 40 R 2 CH 2 (alkyl) 15 to 40 RCH 2 Cl (alkyl chloride) 25 to 50 R 3 CH (alkyl) 25 to 50 RCH 2 NH 2 (alkyl amine) 35 to 50 R 4 C (alkyl) 30 to 40 RCH 2 R (alcohol or ether) 50 to 65 R-CC-R (alkyne) 65 to 90 RCN (nitrile) 110 to 125 R 2 C=CR 2 (alkene) 100 to 150 RC 2 R (acid, ester) 160 to 185 Benzene C (aromatic) 110 to 175 RCH, R 2 C (ald hyde, ketone) 190 to 220 Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) 3200 to 3600 C=C (alkenes) 1620 to H (carbox. acid) 2500 to 3600 C= (ald., ketones) 1710 to 1750 R 2 N-H (amine) 3350 to 3500 C= (acyl halides) 1770 to 1815 sp C-H (alkynes) 3310 to 3320 C= (esters) 1730 to 1750 sp 2 C-H (alkenes) 3000 to 3100 C= (amides) 1680 to 1700 sp 3 C-H (alkanes) 2850 to 2950 sp 2 C- (carbonyls) 1200 triple bond (alkynes) 2100 to 2200 sp 3 C- (alcoh., ethers) 1025 to 1200 triple bond (nitriles) 2240 to 2280 Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstit d benzene 730 to 770, 690 to 710 R 2 C=CH 2 (alkenes) 890 ortho-disubstit d benzene 735 to 770 R 2 C=CHR (alkenes) 790 to 840 meta-disubstit d benzene 750 to 810, 680 to 730 para-disubstituted benzene 790 to 840

23 Chemistry 3720, Spring 2017 Exam 2 - Key Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! #Pi bonds and/or Cycles = [#C - (#H/2) - (#X/2) + #N/2] (8 pts) Provide the major product(s) expected to be formed under the following conditions and then draw a detailed mechanism for the process that includes all important resonance structures where applicable. Why is there only one major product formed here? 1

24 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any regiochemical issues where applicable. 2

25 3. (9 pts) For each of the following molecules, draw a Frost circle and populate the molecular orbitals with the appropriate number of electrons. Then apply Hückel s rule to each system and indicate which molecule(s) is/are aromatic. Give a few words of explanation for your choices. 4. (8 pts) Draw the major final product expected from each of the following reactions: 3

26 5. (18 pts) A new anti-cancer compound has been isolated from a microorganism and is found, from the mass spectrum, to have the formula C12H142 and M + of 190 atomic mass units. The infra-red spectrum has signals at 3500, 1740, 740 and 700 wavenumbers and the proton and carbon spectra are given below. Provide the structure of the unknown and then indicate which signals belong to which atoms in the 1 H NMR spectrum. 1 H NMR (ppm): 0.86 (d, 6H, J = 7.0 Hz); 2.38 (octet, 1H, J = 7.0 Hz); 5.63 (dd, 1H, J = 12.0, 7.0 Hz); 6.35 (d, 1H, J = 12.0 Hz); 7.55 (d, 2H, J = 8.0 Hz); 7.83 (d, 2H, J = 8.0 Hz); (s, 1H). 13 C NMR (ppm): 22.6 (q); 28.0 (d); (d); (d); (s); (d); (s); (d); (s). 4

27 6. (8 pts) Provide the major product that you expected to be formed under the following conditions. Then draw a complete mechanism, including all important resonance structures, for the product s formation. Explain, briefly, why this particular product is major. 7. (7 pts) The 13 C spectrum below belongs to one of the five molecules given. Indicate which one you think matches the NMR data and explain your choice by pointing out which signal matches which carbon(s) and how the coupling data helped inform your decision. 13 C NMR (ppm): 23.3 (q); 33.2 (d); (d); (d); (s); (s); (d). 5

28 8. (6 pts) Provide the major product that you would expect to be formed under each of the following reaction conditions. Then explain the outcomes by discussing the effect of temperature on the reaction pathway. 9. (16 pts) In the boxes provided, draw the expected major product from each step in the following synthetic scheme. Use the clues as needed and be careful if/when stereochemistry/regiochemistry is an issue. 6

29 Chemistry 3720, Spring 2017 Exam 3 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! HDI/Unsaturation Number = [#C atoms ½#H atoms ½#Halogen atoms + ½#N atoms] (8 pts) Give a detailed mechanism for each step in the following conversion of a ketone to a dithioacetal that includes any important resonance structures for intermediates that are formed. Label each step in terms of what kind of event is happening (proton transfer, nucleophilic attack, etc.). 1

30 2. (10 pts) Draw a detailed reaction mechanism for the following nitrile hydrolysis that includes resonance structures for the intermediates that are formed. Label each step in terms of what kind of event is occurring (proton transfer, nucleophilic attack, etc.). 3. (8 pts) Draw a complete reaction mechanism for the following ester saponification process. Label each step in terms of what kind of event is happening (proton transfer, nucleophilic attack, etc.). 2

31 4. (20 pts) Provide the expected major products from each step of the following reaction sequences. Be careful if any stereochemical and/or regiochemical issues arise. 3

32 5. (8 pts) Give the expected major and minor products from the following reaction sequence as well as a detailed mechanism, which includes all resonance structures for intermediate(s) for the formation of both major and minor isomers. Explain briefly the regiochemical distribution of products. 6. (8 pts) Provide a complete mechanism for the following Baeyer-Villager ketone oxidation and then explain the regiochemical outcome. What evidence is given in the product structure to help you decide whether the migration process is step-wise or concerted? 4

33 7. (16 pts) In the boxes below, provide the major product(s) from each step of the following sequence. Using the spectroscopic and molecular formula clues might help you to come up with answers. 8. (8 pts) Make the following molecule from the compounds given on the right. You have access to all of the usual reagents found in an organic lab and you do not need to show retrosynthesis unless it helps. 5

34 9. (7 pts) Draw a complete mechanism for the following crossed-aldol synthesis that describes how the final product is formed. Also include any important resonance structures for intermediates that are formed. 10. (7 pts) Provide a complete step-by-step mechanism for the following acetal hydrolysis that includes any important resonance structures for intermediates that are formed. Label what is happening in each step. 6

35 Youngstown State University rganic Chemistry Spectral Data Sheet Approximate 1 H NMR Chemical Shifts (parts per million) R 3 C-H (alkyl) 0.9 to 1.8 R 3 N-C-H (N neighbor) 2.2 to 2.9 C=C-C-H (allylic) 1.6 to 2.6 Cl-C-H (Cl neighbor) 3.1 to 4.1 =C-C-H (alpha to C=) 2.1 to 2.5 Br-C-H (Br neighbor) 2.7 to 4.1 NC-C-H (alpha to CN) 2.1 to C-H ( neighbor) 3.3 to 3.7 C C H (alkyne) 2.5 R 2 N-H (amine) 1 to 3 Ar-C-H (benzylic) 2.3 to 2.8 R-H (alcohol) 0.5 to 5 C=C-H (alkene) 4.5 to 6.5 Ar--H (phenol) 6 to 8 Ar-H (benzene) 6.5 to 8.5 -C 2 H (carboxylic acid) 10 to 13 =C-H (aldehyde) 9 to 10 Approximate 13 C NMR Chemical Shifts (parts per million) RCH 3 (alkyl) 0 to 35 RCH 2 Br (alkyl bromide) 20 to 40 R 2 CH 2 (alkyl) 15 to 40 RCH 2 Cl (alkyl chloride) 25 to 50 R 3 CH (alkyl) 25 to 50 RCH 2 NH 2 (alkyl amine) 35 to 50 R 4 C (alkyl) 30 to 40 RCH 2 R (alcohol or ether) 50 to 65 R-CC-R (alkyne) 65 to 90 RCN (nitrile) 110 to 125 R 2 C=CR 2 (alkene) 100 to 150 RC 2 R (acid, ester) 160 to 185 Benzene C (aromatic) 110 to 175 RCH, R 2 C (ald hyde, ketone) 190 to 220 Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) 3200 to 3600 C=C (alkenes) 1620 to H (carbox. acid) 2500 to 3600 C= (ald., ketones) 1710 to 1750 R 2 N-H (amine) 3350 to 3500 C= (acyl halides) 1770 to 1815 sp C-H (alkynes) 3310 to 3320 C= (esters) 1730 to 1750 sp 2 C-H (alkenes) 3000 to 3100 C= (amides) 1680 to 1700 sp 3 C-H (alkanes) 2850 to 2950 sp 2 C- (carbonyls) 1200 triple bond (alkynes) 2100 to 2200 sp 3 C- (alcoh., ethers) 1025 to 1200 triple bond (nitriles) 2240 to 2280 Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstit d benzene 730 to 770, 690 to 710 R 2 C=CH 2 (alkenes) 890 ortho-disubstit d benzene 735 to 770 R 2 C=CHR (alkenes) 790 to 840 meta-disubstit d benzene 750 to 810, 680 to 730 para-disubstituted benzene 790 to 840

36 Chemistry 3720, Spring 2017 Exam 3 - Key Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! HDI/Unsaturation Number = [#C atoms ½#H atoms ½#Halogen atoms + ½#N atoms] (8 pts) Give a detailed mechanism for each step in the following conversion of a ketone to a dithioacetal that includes any important resonance structures for intermediates that are formed. Label each step in terms of what kind of event is happening (proton transfer, nucleophilic attack, etc.). 1

37 2. (10 pts) Draw a detailed reaction mechanism for the following nitrile hydrolysis that includes resonance structures for the intermediates that are formed. Label each step in terms of what kind of event is occurring (proton transfer, nucleophilic attack, etc.). 3. (8 pts) Draw a complete reaction mechanism for the following ester saponification process. Label each step in terms of what kind of event is happening (proton transfer, nucleophilic attack, etc.). 2

38 4. (20 pts) Provide the expected major products from each step of the following reaction sequences. Be careful if any stereochemical and/or regiochemical issues arise. 3

39 5. (8 pts) Give the expected major and minor products from the following reaction sequence as well as a detailed mechanism, which includes all resonance structures for intermediate(s) for the formation of both major and minor isomers. Explain briefly the regiochemical distribution of products. 6. (8 pts) Provide a complete mechanism for the following Baeyer-Villager ketone oxidation and then explain the regiochemical outcome. What evidence is given in the product structure to help you decide whether the migration process is step-wise or concerted? 4

40 7. (16 pts) In the boxes below, provide the major product(s) from each step of the following sequence. Using the spectroscopic and molecular formula clues might help you to come up with answers. 8. (8 pts) Make the following molecule from the compounds given on the right. You have access to all of the usual reagents found in an organic lab and you do not need to show retrosynthesis unless it helps. 5

41 9. (7 pts) Draw a complete mechanism for the following crossed-aldol synthesis that describes how the final product is formed. Also include any important resonance structures for intermediates that are formed. 10. (7 pts) Provide a complete step-by-step mechanism for the following acetal hydrolysis that includes any important resonance structures for intermediates that are formed. Label what is happening in each step. 6

42 Chemistry 3720, Spring 2017 Final Exam Student Name: Y Number: This exam is worth 200 points out of a total of 700 points for Chemistry 3720/3720L. You have 120 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! HDI/Unsaturation Number = [#C atoms ½#H atoms ½#Halogen atoms + ½#N atoms] (9 pts) For the following Michael addition, give a complete mechanism, including resonance structures, for the conversion of the enamine into the final product. Explain the observed regioselectivity. 1

43 2. (9 pts) Provide a detailed mechanism for the following tropane alkaloid synthesis that includes resonance structures for any intermediates that are formed. Label what type of event is happening in each step. 3. (9 pts) Draw a complete mechanism for the following ether synthesis that includes all important resonance structures for intermediates that are formed. 2

44 4. (9 pts) Provide a detailed mechanism for the following Gabriel amine synthesis that includes important resonance structures for intermediates that are formed. 5. (8 pts) Give a mechanistic interpretation (push arrows) to show how the enantiomerically pure epoxide is converted to the racemic mxture of products. Include resonance structures for any intermediates formed. 3

45 6. (20 pts) Provide the expected major products from each step of the following synthetic sequences. Be sure to take any stereochemical and regiochemical changes into consideration where applicable. 4

46 7. (14 pts) 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. 8. (8 pts) Provide a retrosynthesis for the following molecule that goes back to the given starting materials. Then, using any of the reactions and reagents encountered in Chemistry 3719/3720, build the molecule. 5

47 9. (14 pts) For the following multi-step biodegradation of amino acids, insert each of the curved arrows needed to describe each bond-making and bond-breaking process. Also label what is happening in each step (proton transfer, nucleophilic attack, etc.). Note: Enz = the enzyme that mediates the process. 6

48 10. (12 pts) Provide the major product from each step of the following reaction sequence. Be careful when regiochemistry is an issue. 11. (10 pts) When attempted, the synthesis below fails to give the indicated product. Explain what the problem is here and then provide a route that will be successful. Include structures of intermediate products. 7

49 12. (16 pts) A newly isolated organic compound has the molecular formula C 13 H 16 2 ; the mass spectrum shows M+ = a.m.u., the IR spectrum shows significant signals at 1740, 1200, and 810 cm -1, and the 1 H and 13 C 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 1 H NMR spectrum. 1 H NMR (CDCl 3 ) ppm : 1.01 (t, 3H, J = 7.0 Hz); 1.73 (sextet, 2H, J = 7.0 Hz); 2.41 (s, 3H); 4.12 (t, 2H, J = 7.0 Hz); 6.31 (d, 1H, J = 16.0 Hz); 7.39 (d, 1H, J = 8.0 Hz); 7.48 (d, 1H, J = 16.0 Hz); 7.59 (d, 1H, J = 8.0 Hz) 13 C NMR (CDCl 3 ) ppm : 10.3 (q); 21.3 (q); 22.0 (t); 67.5 (t); (d); (d, double intensity); (d, double intensity); (s); (s); (d); (s) 8

50 13. (12 pts) Provide a detailed reaction mechanism for the following process that includes all resonance structures for any intermediates that are formed. 14. (12 pts) Draw a detailed mechanism for the following reaction sequence that includes resonance structures for intermediates. Label what is happening in each step (proton transfer, nucleophilic attack, etc.). 9

51 15. (9 pts) Provide a detailed mechanism for the following iodoform reaction that explains the formation of the two products. Make sure to include resonance structures for intermediates. 16. (10 pts) From the molecules shown below, choose the one that one matches the given mass spectrum. Then explain your choice and draw the structure of the fragment that corresponds to the base peak. Atomic masses (in a.m.u.) are as follows: C = 12 ; H = 1 ; = 16 ; F = 19 ; Cl = ; Br =

52 17. (10 pts) The following reaction results in two products that are formed in equal amounts. Give those products as well as a detailed mechanism that describes how they are formed. 18. (9 pts) For each of the following polymers, circle the repeating unit and give starting materials that could be used to synthesize the material. Indicate if each polymer is formed by addition or condensation. 11

53 Youngstown State University rganic Chemistry Spectral Data Sheet Approximate 1 H NMR Chemical Shifts (parts per million) R 3 C-H (alkyl) 0.9 to 1.8 R 3 N-C-H (N neighbor) 2.2 to 2.9 C=C-C-H (allylic) 1.6 to 2.6 Cl-C-H (Cl neighbor) 3.1 to 4.1 =C-C-H (alpha to C=) 2.1 to 2.5 Br-C-H (Br neighbor) 2.7 to 4.1 NC-C-H (alpha to CN) 2.1 to C-H ( neighbor) 3.3 to 3.7 C C H (alkyne) 2.5 R 2 N-H (amine) 1 to 3 Ar-C-H (benzylic) 2.3 to 2.8 R-H (alcohol) 0.5 to 5 C=C-H (alkene) 4.5 to 6.5 Ar--H (phenol) 6 to 8 Ar-H (benzene) 6.5 to 8.5 -C 2 H (carboxylic acid) 10 to 13 =C-H (aldehyde) 9 to 10 Approximate 13 C NMR Chemical Shifts (parts per million) RCH 3 (alkyl) 0 to 35 RCH 2 Br (alkyl bromide) 20 to 40 R 2 CH 2 (alkyl) 15 to 40 RCH 2 Cl (alkyl chloride) 25 to 50 R 3 CH (alkyl) 25 to 50 RCH 2 NH 2 (alkyl amine) 35 to 50 R 4 C (alkyl) 30 to 40 RCH 2 R (alcohol or ether) 50 to 65 R-CC-R (alkyne) 65 to 90 RCN (nitrile) 110 to 125 R 2 C=CR 2 (alkene) 100 to 150 RC 2 R (acid, ester) 160 to 185 Benzene C (aromatic) 110 to 175 RCH, R 2 C (ald hyde, ketone) 190 to 220 Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) 3200 to 3600 C=C (alkenes) 1620 to H (carbox. acid) 2500 to 3600 C= (ald., ketones) 1710 to 1750 R 2 N-H (amine) 3350 to 3500 C= (acyl halides) 1770 to 1815 sp C-H (alkynes) 3310 to 3320 C= (esters) 1730 to 1750 sp 2 C-H (alkenes) 3000 to 3100 C= (amides) 1680 to 1700 sp 3 C-H (alkanes) 2850 to 2950 sp 2 C- (carbonyls) 1200 triple bond (alkynes) 2100 to 2200 sp 3 C- (alcoh., ethers) 1025 to 1200 triple bond (nitriles) 2240 to 2280 Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstit d benzene 730 to 770, 690 to 710 R 2 C=CH 2 (alkenes) 890 ortho-disubstit d benzene 735 to 770 R 2 C=CHR (alkenes) 790 to 840 meta-disubstit d benzene 750 to 810, 680 to 730 para-disubstituted benzene 790 to 840

54 Spring 2016 Page File 55 Spring 2016 Exam 1 62 Spring 2016 Exam 1 Key 68 Spring 2016 Exam 2 74 Spring 2016 Exam 2 Key 81 Spring 2016 Exam 3 88 Spring 2016 Exam 3 Key 94 Spring 2016 Final (No Key)

55 Chemistry 3720, Spring 2016 Exam 1 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! 1. (8 pts) Give the major products from each step of the reaction sequences below and then show whether the highlighted carbon atoms have been oxidized, reduced or unchanged in each step by assigning each an oxidation number. 1

56 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any stereochemical changes where applicable. 2

57 3. (9 pts) The following ketone synthesis is impossible to complete under the given conditions. Explain why and give reagents that would allow for access to the ketone. Include structures of intermediate products. 4. (8 pts) Draw a complete mechanism for the following ester to ether conversion. 3

58 5. (7 pts) The mass spectrum below belongs to one of the four compounds shown. Indicate which molecule the spectrum belongs to and explain why you chose that one and not the other three. Atomic masses (in atomic mass units, a.m.u.) are as follows: C = 12 ; H = 1 ; = 16 ; F = 19 ; Cl = ; Br = (7 pts) Which of the following molecules matches this IR spectrum? Point out important signals that helped you to decide on your choice and why the spectrum does not match the other possibilities. 4

59 7. (16 pts) In the boxes below, give the major product(s) from each step of the following sequence. The given spectroscopic and molecular formula clues might help you to work out the answers. 8. (9 pts) Draw the structures of each of the following molecules and then provide the reagents needed to convert each of the given starting materials into the required product. 5

60 9. (8 pts) Within each of the following pairs of molecules circle the one required for the answer and give a few words of explanation for your choice. 10. (8 pts) Provide a suitable organic compound that would serve as a precursor (starting material) for each of the following molecules under the given conditions. 6

61 Youngstown State University rganic Chemistry Spectral Data Sheet Approximate 1 H NMR Chemical Shifts (parts per million) R 3 C-H (alkyl) 0.9 to 1.8 R 3 N-C-H (N neighbor) 2.2 to 2.9 C=C-C-H (allylic) 1.6 to 2.6 Cl-C-H (Cl neighbor) 3.1 to 4.1 =C-C-H (alpha to C=) 2.1 to 2.5 Br-C-H (Br neighbor) 2.7 to 4.1 NC-C-H (alpha to CN) 2.1 to C-H ( neighbor) 3.3 to 3.7 C C H (alkyne) 2.5 R 2 N-H (amine) 1 to 3 Ar-C-H (benzylic) 2.3 to 2.8 R-H (alcohol) 0.5 to 5 C=C-H (alkene) 4.5 to 6.5 Ar--H (phenol) 6 to 8 Ar-H (benzene) 6.5 to 8.5 -C 2 H (carboxylic acid) 10 to 13 =C-H (aldehyde) 9 to 10 Approximate 13 C NMR Chemical Shifts (parts per million) RCH 3 (alkyl) 0 to 35 RCH 2 Br (alkyl bromide) 20 to 40 R 2 CH 2 (alkyl) 15 to 40 RCH 2 Cl (alkyl chloride) 25 to 50 R 3 CH (alkyl) 25 to 50 RCH 2 NH 2 (alkyl amine) 35 to 50 R 4 C (alkyl) 30 to 40 RCH 2 R (alcohol or ether) 50 to 65 R-CC-R (alkyne) 65 to 90 RCN (nitrile) 110 to 125 R 2 C=CR 2 (alkene) 100 to 150 RC 2 R (acid, ester) 160 to 185 Benzene C (aromatic) 110 to 175 RCH, R 2 C (ald hyde, ketone) 190 to 220 Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) 3200 to 3600 C=C (alkenes) 1620 to H (carbox. acid) 2500 to 3600 C= (ald., ketones) 1710 to 1750 R 2 N-H (amine) 3350 to 3500 C= (acyl halides) 1770 to 1815 sp C-H (alkynes) 3310 to 3320 C= (esters) 1730 to 1750 sp 2 C-H (alkenes) 3000 to 3100 C= (amides) 1680 to 1700 sp 3 C-H (alkanes) 2850 to 2950 sp 2 C- (carbonyls) 1200 triple bond (alkynes) 2100 to 2200 sp 3 C- (alcoh., ethers) 1025 to 1200 triple bond (nitriles) 2240 to 2280 Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstit d benzene 730 to 770, 690 to 710 R 2 C=CH 2 (alkenes) 890 ortho-disubstit d benzene 735 to 770 R 2 C=CHR (alkenes) 790 to 840 meta-disubstit d benzene 750 to 810, 680 to 730 para-disubstituted benzene 790 to 840

62 Chemistry 3720, Spring 2016 Exam 1 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! 1. (8 pts) Give the major products from each step of the reaction sequences below and then show whether the highlighted carbon atoms have been oxidized or reduced in each step by assigning each an oxidation number. 1

63 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any stereochemical changes where applicable. 2

64 3. (9 pts) The following ketone synthesis is impossible to complete under the given conditions. Explain why and give reagents that would allow for access to the ketone. Include structures of intermediate products. 4. (8 pts) Draw a complete mechanism for the following ester to ether conversion. 3

65 5. (7 pts) The mass spectrum below belongs to one of the four compounds shown. Indicate which molecule the spectrum belongs to and explain why you chose that one and not the other three. Atomic masses (in atomic mass units, a.m.u.) are as follows: C = 12 ; H = 1 ; = 16 ; F = 19 ; Cl = ; Br = (7 pts) Which of the following molecules matches this IR spectrum? Point out important signals that helped you to decide on your choice and why the spectrum does not match the other possibilities. The strong signal at ~1720 cm -1 indicates a carbonyl which a) and b) don t have; d) would need an H at cm -1. 4

66 7. (16 pts) In the boxes below, give the major product(s) from each step of the following sequence. The given spectroscopic and molecular formula clues might help you to work out the answers. 8. (9 pts) Draw the structures of each of the following molecules and then provide the reagents needed to convert each of the given starting materials into the required product. 5

67 9. (8 pts) Within each of the following pairs of molecules circle the one required for the answer and give a few words of explanation for your choice. 10. (8 pts) Provide a suitable organic compound that would serve as a precursor (starting material) for each of the following molecules under the given conditions. 6

68 Chemistry 3720, Spring 2016 Exam 2 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! #Pi bonds and/or Cycles = [#C - (#H/2) - (#X/2) + #N/2] (8 pts) Provide the major product(s) expected to be formed under the following conditions and then draw a detailed mechanism for the process that includes all important resonance structures where applicable. 1

69 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any stereochemical changes where applicable. 2

70 3. (9 pts) In the following experiments a diene is reacted with a dienophile at high temperature. Decide which reactions will give a cycloaddition product and which will not. For those that do, draw the structure of the major cycloadduct; for those that do not, give a brief explanation. 4. (8 pts) For the following molecular orbital diagrams used in describing the interactions of reactants in the Diels-Alder reaction, shade in the orbitals as needed to describe the orbital interactions at each energy level. Then populate each set of orbitals with the appropriate number of electrons and indicate in each reactant which orbital is the highest occupied M.. and which is the lowest unoccupied M.. 3

71 5. (18 pts) An unknown organic molecule has been isolated from a tropical plant and is found, from the mass spectrum, to have the formula C 12 H 13 N and M + of 187 atomic mass units. The infra-red spectrum has signals at 2250, 1720, 760, and 690 wavenumbers and the proton and carbon spectra are given below. Provide the structure of the unknown and then indicate which signals belong to which atoms in the 1 H NMR spectrum. 1 H NMR (ppm): 1.18 (t, 3H, J = 7.0 Hz); 2.60 (t, 2H, J = 6.9 Hz); 2.72 (q, 2H, J = 7.0 Hz); 2.92 (t, 2H, J = 6.9 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). 13 C NMR (ppm): 11.8 (t); 14.5 (q); 28.2 (t); 34.3 (t); (s); (d); (d); (d); (d); (s); (s); (s). 4

72 6. (8 pts) Provide a complete mechanism for the following Friedel-Crafts alkylation that includes resonance structures for the sigma complex that is formed as an intermediate. 7. (7 pts) The proton spectrum below belongs to one of the five molecules given. Indicate which one you think matches the NMR data and explain your choice by pointing out which signal matches which proton(s) and how the coupling constant data helped inform your decision. 1 H NMR (ppm): 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 Hz); 6.88 (d, 1H, J = 16 Hz). 5

73 8. (6 pts) Treatment of the following diene with HBr above room temperature leads to two addition products, one of which is major. Draw the two products and a mechanism for their formation; then explain briefly the isomer distribution observed at this temperature. 9. (6 pts) Benzene is aromatic but cyclobutadiene is antiaromatic. Draw Frost circles for each molecule and use them to explain briefly why benzene is so stable and cyclobutadiene is so unstable. 10. (10 pts) In the boxes provided, draw the expected major product from each step in the following synthetic scheme. 6

74 Youngstown State University rganic Chemistry Spectral Data Sheet Approximate 1 H NMR Chemical Shifts (parts per million) R 3 C-H (alkyl) 0.9 to 1.8 R 3 N-C-H (N neighbor) 2.2 to 2.9 C=C-C-H (allylic) 1.6 to 2.6 Cl-C-H (Cl neighbor) 3.1 to 4.1 =C-C-H (alpha to C=) 2.1 to 2.5 Br-C-H (Br neighbor) 2.7 to 4.1 NC-C-H (alpha to CN) 2.1 to C-H ( neighbor) 3.3 to 3.7 C C H (alkyne) 2.5 R 2 N-H (amine) 1 to 3 Ar-C-H (benzylic) 2.3 to 2.8 R-H (alcohol) 0.5 to 5 C=C-H (alkene) 4.5 to 6.5 Ar--H (phenol) 6 to 8 Ar-H (benzene) 6.5 to 8.5 -C 2 H (carboxylic acid) 10 to 13 =C-H (aldehyde) 9 to 10 Approximate 13 C NMR Chemical Shifts (parts per million) RCH 3 (alkyl) 0 to 35 RCH 2 Br (alkyl bromide) 20 to 40 R 2 CH 2 (alkyl) 15 to 40 RCH 2 Cl (alkyl chloride) 25 to 50 R 3 CH (alkyl) 25 to 50 RCH 2 NH 2 (alkyl amine) 35 to 50 R 4 C (alkyl) 30 to 40 RCH 2 R (alcohol or ether) 50 to 65 R-CC-R (alkyne) 65 to 90 RCN (nitrile) 110 to 125 R 2 C=CR 2 (alkene) 100 to 150 RC 2 R (acid, ester) 160 to 185 Benzene C (aromatic) 110 to 175 RCH, R 2 C (ald hyde, ketone) 190 to 220 Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) 3200 to 3600 C=C (alkenes) 1620 to H (carbox. acid) 2500 to 3600 C= (ald., ketones) 1710 to 1750 R 2 N-H (amine) 3350 to 3500 C= (acyl halides) 1770 to 1815 sp C-H (alkynes) 3310 to 3320 C= (esters) 1730 to 1750 sp 2 C-H (alkenes) 3000 to 3100 C= (amides) 1680 to 1700 sp 3 C-H (alkanes) 2850 to 2950 sp 2 C- (carbonyls) 1200 triple bond (alkynes) 2100 to 2200 sp 3 C- (alcoh., ethers) 1025 to 1200 triple bond (nitriles) 2240 to 2280 Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstit d benzene 730 to 770, 690 to 710 R 2 C=CH 2 (alkenes) 890 ortho-disubstit d benzene 735 to 770 R 2 C=CHR (alkenes) 790 to 840 meta-disubstit d benzene 750 to 810, 680 to 730 para-disubstituted benzene 790 to 840

75 Chemistry 3720, Spring 2016 Exam 2 - Key Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! #Pi bonds and/or Cycles = [#C - (#H/2) - (#X/2) + #N/2] (8 pts) Provide the major product(s) expected to be formed under the following conditions and then draw a detailed mechanism for the process that includes all important resonance structures where applicable. 1

76 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any stereochemical changes where applicable. 2

77 3. (9 pts) In the following experiments a diene is reacted with a dienophile at high temperature. Decide which reactions will give a cycloaddition product and which will not. For those that do, draw the structure of the major cycloadduct; for those that do not, give a brief explanation. 4. (8 pts) For the following molecular orbital diagrams used in describing the interactions of reactants in the Diels-Alder reaction, shade in the orbitals as needed to describe the orbital interactions at each energy level. Then populate each set of orbitals with the appropriate number of electrons and indicate in each reactant which orbital is the highest occupied M.. and which is the lowest unoccupied M.. 3

78 5. (18 pts) An unknown organic molecule has been isolated from a tropical plant and is found, from the mass spectrum, to have the formula C 12 H 13 N and M + of 187 atomic mass units. The infra-red spectrum has signals at 2250, 1720, 760, and 690 wavenumbers and the proton and carbon spectra are given below. Provide the structure of the unknown and then indicate which signals belong to which atoms in the 1 H NMR spectrum. 1 H NMR (ppm): 1.18 (t, 3H, J = 7.0 Hz); 2.60 (t, 2H, J = 6.9 Hz); 2.72 (q, 2H, J = 7.0 Hz); 2.92 (t, 2H, J = 6.9 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). 13 C NMR (ppm): 11.8 (t); 14.5 (q); 28.2 (t); 34.3 (t); (s); (d); (d); (d); (d); (s); (s); (s). 4

79 6. (8 pts) Provide a complete mechanism for the following Friedel-Crafts alkylation that includes resonance structures for the sigma complex that is formed as an intermediate. 7. (7 pts) The proton spectrum below belongs to one of the five molecules given. Indicate which one you think matches the NMR data and explain your choice by pointing out which signal matches which proton(s) and how the coupling constant data helped inform your decision. 1 H NMR (ppm): 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 Hz); 6.88 (d, 1H, J = 16 Hz). The 16 Hz coupling constant matches the trans alkene. 5

80 8. (6 pts) Treatment of the following diene with HBr above room temperature leads to two addition products, one of which is major. Draw the two products and a mechanism for their formation; then explain briefly the isomer distribution observed at this temperature. The 1,4-adduct is favored here because the higher temperature allows for the additions to be reversible. This will allow for an equilibrium favoring the more stable alkene, i.e. the 1,4-isomer. 9. (6 pts) Benzene is aromatic but cyclobutadiene is antiaromatic. Draw Frost circles for each molecule and use them to explain briefly why benzene is so stable and cyclobutadiene is so unstable. All of the available electrons in the benzene case go into bonding orbitals and so stabilize this molecule whereas the second pair of electrons in cyclobutadiene have to be split into two separate non-bonding orbitals thereby destabilizing the molecule and making it anti-aromatic. 10. (10 pts) In the boxes provided, draw the expected major product from each step in the following synthetic scheme. 6

81 Chemistry 3720, Spring 2016 Exam 3 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! #Pi bonds and/or Cycles = [#C - (#H/2) - (#X/2) + #N/2] (8 pts) Provide the major product(s) expected to be formed under the following conditions and then draw a detailed mechanism for the process. 1

82 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any stereochemical changes where applicable. 2

83 3. (14 pts) In the boxes provided, draw the expected major product from each step in the following synthetic scheme. 4. (8 pts) Provide a product and a complete mechanism for the following reaction that includes resonance structures for the charged complex that is formed as an intermediate. 3

84 5. (10 pts) An efficient synthesis of the following molecule is not as straightforward as it might appear. Explain why and then give the reagents required to make the molecule in high yield starting from benzene. Give the structures of all intermediate products in your synthesis. 6. (8 pts) Provide the reagents and conditions needed to convert each starting material into the given product. More than one set of reagents may be required in each case. 4

85 7. (8 pts) In the following reaction two regioisomeric bromides are produced as shown. Decide which product is major, then give a mechanism for its formation, including all important resonance structures. Finally, explain briefly the regioselectivity observed. 8. (8 pts) Provide a mechanism for the following lactone formation that includes all of the important resonance structures for any intermediates that are formed. Explain briefly the role of anhydrous MgS4 in this process. 5

86 9. (8 pts) Produce a retrosynthetic analysis for the following molecule that goes back to 1-butanol as the only source of carbon. Then give a synthesis of the molecule that includes structures of any intermediate products that are formed on the way. Assume you have access to any reagents required and that mixtures are separable. 10. (8 pts) In the boxes provided, draw an appropriate starting material that would provide the given products under the conditions shown. 6

87 Youngstown State University rganic Chemistry Spectral Data Sheet Approximate 1 H NMR Chemical Shifts (parts per million) R 3 C-H (alkyl) 0.9 to 1.8 R 3 N-C-H (N neighbor) 2.2 to 2.9 C=C-C-H (allylic) 1.6 to 2.6 Cl-C-H (Cl neighbor) 3.1 to 4.1 =C-C-H (alpha to C=) 2.1 to 2.5 Br-C-H (Br neighbor) 2.7 to 4.1 NC-C-H (alpha to CN) 2.1 to C-H ( neighbor) 3.3 to 3.7 C C H (alkyne) 2.5 R 2 N-H (amine) 1 to 3 Ar-C-H (benzylic) 2.3 to 2.8 R-H (alcohol) 0.5 to 5 C=C-H (alkene) 4.5 to 6.5 Ar--H (phenol) 6 to 8 Ar-H (benzene) 6.5 to 8.5 -C 2 H (carboxylic acid) 10 to 13 =C-H (aldehyde) 9 to 10 Approximate 13 C NMR Chemical Shifts (parts per million) RCH 3 (alkyl) 0 to 35 RCH 2 Br (alkyl bromide) 20 to 40 R 2 CH 2 (alkyl) 15 to 40 RCH 2 Cl (alkyl chloride) 25 to 50 R 3 CH (alkyl) 25 to 50 RCH 2 NH 2 (alkyl amine) 35 to 50 R 4 C (alkyl) 30 to 40 RCH 2 R (alcohol or ether) 50 to 65 R-CC-R (alkyne) 65 to 90 RCN (nitrile) 110 to 125 R 2 C=CR 2 (alkene) 100 to 150 RC 2 R (acid, ester) 160 to 185 Benzene C (aromatic) 110 to 175 RCH, R 2 C (ald hyde, ketone) 190 to 220 Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) 3200 to 3600 C=C (alkenes) 1620 to H (carbox. acid) 2500 to 3600 C= (ald., ketones) 1710 to 1750 R 2 N-H (amine) 3350 to 3500 C= (acyl halides) 1770 to 1815 sp C-H (alkynes) 3310 to 3320 C= (esters) 1730 to 1750 sp 2 C-H (alkenes) 3000 to 3100 C= (amides) 1680 to 1700 sp 3 C-H (alkanes) 2850 to 2950 sp 2 C- (carbonyls) 1200 triple bond (alkynes) 2100 to 2200 sp 3 C- (alcoh., ethers) 1025 to 1200 triple bond (nitriles) 2240 to 2280 Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstit d benzene 730 to 770, 690 to 710 R 2 C=CH 2 (alkenes) 890 ortho-disubstit d benzene 735 to 770 R 2 C=CHR (alkenes) 790 to 840 meta-disubstit d benzene 750 to 810, 680 to 730 para-disubstituted benzene 790 to 840

88 Chemistry 3720, Spring 2016 Exam 3 - Key Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! #Pi bonds and/or Cycles = [#C - (#H/2) - (#X/2) + #N/2] (8 pts) Provide the major product(s) expected to be formed under the following conditions and then draw a detailed mechanism for the process. 1

89 2. (20 pts) Draw the expected major products from each step of the following reaction sequences. Make sure you take into account any stereochemical changes where applicable. 2

90 3. (14 pts) In the boxes provided, draw the expected major product from each step in the following synthetic scheme. 4. (8 pts) Provide a product and a complete mechanism for the following reaction that includes resonance structures for the charged complex that is formed as an intermediate. 3

91 5. (10 pts) An efficient synthesis of the following molecule is not as straightforward as it might appear. Explain why and then give the reagents required to make the molecule in high yield starting from benzene. Give the structures of all intermediate products in your synthesis. 6. (8 pts) Provide the reagents and conditions needed to convert each starting material into the given product. More than one set of reagents may be required in each case. 4

92 7. (8 pts) In the following reaction two regioisomeric bromides are produced as shown. Decide which product is major, then give a mechanism for its formation, including all important resonance structures. Finally, explain briefly the regioselectivity observed. 8. (8 pts) Provide a mechanism for the following lactone formation that includes all of the important resonance structures for any intermediates that are formed. Explain briefly the role of anhydrous MgS4 in this process. 5

93 9. (8 pts) Produce a retrosynthetic analysis for the following molecule that goes back to 1-butanol as the only source of carbon. Then give a synthesis of the molecule that includes structures of any intermediate products that are formed on the way. Assume you have access to any reagents required and that mixtures are separable. 10. (8 pts) In the boxes provided, draw an appropriate starting material that would provide the given products under the conditions shown. 6

94 Chemistry 3720, Spring 2016 Final Exam Student Name: Y Number: This exam is worth 200 points out of a total of 700 points for Chemistry 3720/3720L. You have 120 minutes to complete the exam. The spectroscopy sheet is attached as the last page. Good Luck! HDI/Unsaturation Number = [#C atoms ½#H atoms ½#Halogen atoms + ½#N atoms] (9 pts) For the following Baeyer-Villager reaction, give a complete mechanism, including any resonance structures, for the conversion of the ketone into the final product. Explain the observed regioselectivity. 1

95 2. (9 pts) Provide a detailed mechanism for the following Wittig synthesis that includes resonance structures for any intermediates that are formed. Br 1. PPh 3, ether 2. LDA, THF H 3 C CH 3 3. H 3 C CH 3 3. (9 pts) Draw a complete mechanism for the following Gabriel amine synthesis that includes any resonance structures for intermediates that are formed. 2

96 4. (10 pts) Provide a detailed mechanism for the following Robinson synthesis that includes all important resonance structures for intermediates that are formed. Use R groups for brevity where possible. 5. (8 pts) Give the two major products that are formed from the following crown ether under the conditions provided and then a detailed mechanism for their formation. 3

97 6. (20 pts) Provide the expected major products from each step of the following reaction sequences. Be sure to take tautomerism into consideration where applicable. 4

98 7. (14 pts) 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. 8. (8 pts) ne of the most common organic polymers used in 3D printing is polylactic acid (PLA), which is derived from corn and is biodegradable. Provide a detailed mechanism, including any important resonance structures for how the two lactic acid units shown below come together to give the polymer linkage. 5

99 9. (15 pts) For the following multi-step laboratory synthesis of the amino acid (+/-)-proline, provide detailed mechanisms, including important resonance structures, for steps A, C, E, F and G. CN Et Et Ni/H Et Et 2 Et Et NaEt (- EtH) A CN B C NH 2 HN C 2 Et SCl 2 HN Cl C 2 Et H 3 +, (- C 2 ) NH 3 Cl Cl C 2 H i. H ii. HCl N H2 C 2 H D E F G i. H N H C 2 6

100 10. (12 pts) Provide a retrosynthesis for this molecule that goes back to 1-butanol as the only source of carbon. Then build the molecule in the forward direction showing the product from each step. 11. (10 pts) The 1 H spectrum below belongs to one of the five molecules given. Indicate which one you think matches the NMR data and explain your choice by pointing out which signal matches which proton(s) PPM 1 H NMR (ppm): 0.98 (d, 6H, J = 7.0 Hz); 1.18 (t, 3H, J = 6.9 Hz); 2.21 (multiplet, 1H, J = 7.0 Hz); 2.72 (q, 2H, J = 6.9 Hz); 2.88 (d, 2H, J = 7.0 Hz); 6.80 (d, 2H, J = 6.8 Hz); 6.90 (s, 2H, J = 6.8 Hz). 7

101 12. (12 pts) For each of the following series of molecules, circle the one that is asked for, then give a brief explanation for your choices. 13. (8 pts) Give the major product(s) expected to be formed under the following conditions, and then draw a detailed mechanism that includes any important resonance structures. Why is/are your product(s) major? 8

102 14. (16 pts) An unknown organic compound has the molecular formula C 11 H 14 3 ; the mass spectrum shows M+ = a.m.u., the IR spectrum shows significant signals at 1740, 1200, and 800 cm -1, and the 1 H and 13 C 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 1 H NMR spectrum PPM 1 H NMR (CDCl 3 ) ppm : 1.01 (t, 3H, J = 7.1 Hz), 1.91 (sextet, 2H, J = 7.1 Hz), 3.81 (singlet, 3H), 4.30 (t, 2H, J = 7.1 Hz), 6.85 (d, 2H, J = 6.8 Hz), 7.94 (d, 2H, J = 6.8 Hz) PPM C NMR (CDCl 3 ) ppm : 10.3 (q), 21.9 (t), 55.8 (q), 68.8 (t), (d), (s), (d), (s), (s) 9

103 15. (8 pts) Indicate which product will be major, then give a detailed mechanism for its formation that includes resonance structures for any intermediates that are formed. Why is that product major? 16. (10 pts) Give a complete mechanism for this process that includes any important resonance structures. 10

104 17. (12 pts) Give the products from each step of the following synthetic sequence and then, on the NMR axis given below, draw the expected 1 H spectrum of the final product. 18. (10 pts) The following molecule is lactose, which is found in milk, and is made up of one galactose and one glucose subunit. When this molecule is treated with H + /H2 it is hydrolyzed to the two individual monosaccharides. Draw structures of the D-galactose and D-glucose products and a mechanism for their formation, including any important resonance structures. 11

105 Spring 2015 Page File 106 Spring 2015 Exam Spring 2015 Exam 1 Key 119 Spring 2015 Exam Spring 2015 Exam 2 Key 132 Spring 2015 Exam Spring 2015 Exam 3 Key 144 Spring 2015 Final (No Key)

106 Chemistry 3720, Spring 2015 Exam 1 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached at the back of the exam. Good Luck! 1. (8 pts) 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). 1

107 2. (20 pts) Provide the expected major products from each step of the following reaction sequences. Be sure to include any stereochemical changes where applicable. a. 1. NaBH 4,CH 3 H 2. NaH, THF 3. CH 3 Br b. CH 3 1. m-cpba, CH 2 Cl 2 2. PhMgBr, THF 3. NH 4 Cl (aq) c. H 1. PDC, CH 2 Cl 2 2. CH 3 MgBr, ether 3. H 3 + (quench) d. SiMe 3 Me 1. xs CH 3 MgBr, ether 2. H 3 + (quench) 3. (C 4 H 9 ) 4 N + F - e. Me H H 1. PCC, CH 2 Cl 2 2. TsCl, pyridine 3. KtBu, THF 2

108 3. (9 pts) Give the products expected to be formed from each step under the following conditions. Then draw complete mechanisms for each of the conversions. 4. (8 pts) 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 ; = 16 ; F = 19 ; Cl = ; Br = H Br a) b) c) Cl d) F CH 3 CH 3 CH 3 CH 3 3

109 5. (14 pts) In the boxes below, provide the product(s) from each step of the following sequence. Using the spectroscopic and molecular formula clues might help you come up with answers. 6. (8 pts) Give the major product(s) expected to be formed under the following conditions as well as a complete mechanism for its/their formation. 4

110 7. (8 pts) Give the expected product(s) from each step of the following reaction sequence, and then provide a mechanism for each synthetic step. 8. (8 pts) 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/ Include a product from each of your synthetic steps. 5

111 9. (9 pts) 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 pts) 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. 6

112 Approximate 1 H NMR Chemical Shifts (δ, ppm) Youngstown State University rganic Chemistry Spectral Data Sheet R 3 C-H (alkyl) R 3 N-C-H (N neighbor) C=C-C-H (allylic) Cl-C-H (Cl neighbor) =C-C-H (α to C=) Br-C-H (Br neighbor) NC-C-H (α to CN) C-H ( neighbor) C C H (alkyne) 2.5 R 2 N-H (amine) 1-3 Ar-C-H (benzylic) R-H (alcohol) C=C-H (alkene) Ar--H (phenol) 6-8 Ar-H (benzene) C 2 H (carboxylic acid) =C-H (aldehyde) 9-10 Approximate 13 C NMR Chemical Shifts (δ, ppm) RCH 3 (alkyl) 0-35 RCH 2 Br (alkyl bromide) R 2 CH 2 (alkyl) RCH 2 Cl (alkyl chloride) R 3 CH (alkyl) RCH 2 NH 2 (alkyl amine) R 4 C (alkyl) RCH 2 R (alcohol or ether) R C C R (alkyne) RCN (nitrile) R 2 C=CR 2 (alkene) RC 2 R (acid, ester) Benzene C (aromatic) RCH, R 2 C (aldehyde, ketone) Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) C=C (alkenes) H (carbox. acid) C= (ald., ketones) R 2 N-H (amine) C= (acyl halides) sp C-H (alkynes) C= (esters) sp 2 C-H (alkenes) C= (amides) sp 3 C-H (alkanes) sp 2 C- (carbonyls) 1200 triple bond (alkynes) sp 3 C- (alcoh., ethers) triple bond (nitriles) Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstituted benzene , R 2 C=CH 2 (alkenes) 890 ortho-disubstituted benzene R 2 C=CHR (alkenes) meta-disubstituted benzene , para-disubstituted benzene

113 Chemistry 3720, Spring 2015 Exam 1 - Key Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached at the back of the exam. Good Luck! 1. (8 pts) 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). 1. xs LiAlH 4,THF 2. H 2 H H H H [H AlH 3 ] H H H H H H H H [H AlH 3 ] 1

114 2. (20 pts) Provide the expected major products from each step of the following reaction sequences. Be sure to include any stereochemical changes where applicable. a. 1. NaBH 4,CH 3 H 2. NaH, THF 3. CH 3 Br 1. H CH 3 (+/-) (+/-) (+/-) b. 1. CH 2. CH 1. m-cpba, CH 2 Cl 3 CH 3 3. CH H 2. PhMgBr, THF Ph Ph 3. NH 4 Cl (aq) (+/-) (+/-) (+/-) c. H 1. PDC, CH 2 Cl CH CH 3 MgBr, ether 3. H 3 + (quench) (+/-) (+/-) H CH 3 d. SiMe 3 Me 1. xs CH 3 MgBr, ether 2. H 3 + (quench) 3. (C 4 H 9 ) 4 N + F H 3. CH 3 CH 3 CH 3 CH 3 SiMe 3 SiMe 3 H H CH 3 CH 3 e. Me 1. Me 2. Me 3. H 1. PCC, CH 2 Cl 2 H Ts H 2. TsCl, pyridine 3. KtBu, THF Me 2

115 3. (9 pts) Give the products expected to be formed from each step under the following conditions. Then draw complete mechanisms for each of the conversions. CH 2 Br 1. NaSH, DMF CH 2 SCH 2 CH 2 CH 3 2. NaH, THF 3. CH 3 CH 2 CH 2 Br Br CH 2 S H Na :H CH 2 S 4. (8 pts) 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 ; F = 19 ; Cl = ; Br = 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. 3

116 5. (14 pts) In the boxes below, provide the product(s) from each step of the following sequence. Using the spectroscopic and molecular formula clues might help you come up with answers. 6. (8 pts) 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 S N 1 and S N 2 reactions do not occur at sp 2 C. 4

117 7. (8 pts) Give the expected product(s) from each step of the following reaction sequence, and then provide a mechanism for each synthetic step. 8. (8 pts) 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/ Include a product from each of your synthetic steps. Retrosynthesis Br H H H Br MgBr H H Synthesis H PCC CH 2 Cl 2 H MgBr aq. NH 4 Cl H Br Mg MgBr ether NaH, THF H PBr 3 Br Br Na 5

118 9. (9 pts) 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 H group, most likely in an alcohol. The carboxylic acid would have a C= signal around ~1750, which is absent here; the ether would not have the strong H signal at ~3300 ; the ketone would show a strong C= signal at ~1730, which is absent here. 10. (8 pts) 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. 6

119 Chemistry 3720, Spring 2015 Exam 2 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached at the back of the exam. Good Luck! HDI/Unsaturation Number = [#C atoms ½#H atoms ½#Halogen atoms + ½#N atoms] (9 pts) 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 1 H NMR of the product. 1

120 2. (20 pts) Provide the expected major products from each step of the following reaction sequences. Be sure to include any stereochemical changes where applicable. a. + H 1. PhMe, reflux 2. Na 2 Cr 2 7,H 2 S 4 b. 1. Br 2, heat 2. KtBu 3. m-cpba c. 1. Zn, HCl 2. Na 2 Cr 2 7,H 2 S 4 d. 1. HBr 2. NaCN, DMF e. H 1. HN 3,H 2 S 4 2. Sn, HCl 2

121 3. (9 pts) 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. a. b. c. 4. (9 pts) 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. a. b. c. H H d. H e. f. 1 H NMR (CDCl 3 ) ppm: 1.05 (s, 9H), 5.83 (d, 1H, J = 16 Hz), 6.71 (d, 1H, J = 16 Hz), (m, 5H). 13 C NMR (CDCl 3 ) ppm: 29.5 (q, triple intensity), 32.9 (s), (d), (d, double intensity), (d), (d, double intensity), (s), (d), (s). 3

122 5. (14 pts) 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. CH 3 CCl, AlCl 3 NaBH 4,CH 3 H IR : 1740 cm -1 [ ] D =0 PBr 3 D 2 Mg, ether 1 H NMR: 0.98, 3H d C 8 H 9 MgBr MS: M + = 184, M+2 = 186 Cl,AlCl 3 Zn, HCl Final product: Molecular formula = C 13 H 19 D 13 C NMR: 9 signals 6. (8 pts) 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. 4

123 7. (14 pts) An unknown organic compound has the molecular formula C 13 H 18 2 ; the mass spectrum shows M+ = 206 a.m.u., the IR spectrum shows significant signals at 1720, 1200, and 800 cm -1, and the 1 H and 13 C 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 1 H NMR spectrum. 1 H NMR (CDCl 3 ) 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). 13 C NMR (CDCl 3 ) ppm : 13.6 (q), 17.4 (t), 22.0 (q, double intensity), 40.4 (t), 75.8 (d), (d, double intensity), (d, double intensity), (s), (s), (s) 5

124 8. (9 pts) Provide a detailed mechanism for the following transformation that includes all important resonance structures for the intermediate involved. Then explain, briefly, the observed regioselectivity. C N C N Br 2,FeBr 3 Br 9. (8 pts) Which of the following diene compounds do you expect to participate in Diels-Alder reactions and which will not? Explain your choices. a. b. c. d. 6

125 Approximate 1 H NMR Chemical Shifts (δ, ppm) Youngstown State University rganic Chemistry Spectral Data Sheet R 3 C-H (alkyl) R 3 N-C-H (N neighbor) C=C-C-H (allylic) Cl-C-H (Cl neighbor) =C-C-H (α to C=) Br-C-H (Br neighbor) NC-C-H (α to CN) C-H ( neighbor) C C H (alkyne) 2.5 R 2 N-H (amine) 1-3 Ar-C-H (benzylic) R-H (alcohol) C=C-H (alkene) Ar--H (phenol) 6-8 Ar-H (benzene) C 2 H (carboxylic acid) =C-H (aldehyde) 9-10 Approximate 13 C NMR Chemical Shifts (δ, ppm) RCH 3 (alkyl) 0-35 RCH 2 Br (alkyl bromide) R 2 CH 2 (alkyl) RCH 2 Cl (alkyl chloride) R 3 CH (alkyl) RCH 2 NH 2 (alkyl amine) R 4 C (alkyl) RCH 2 R (alcohol or ether) R C C R (alkyne) RCN (nitrile) R 2 C=CR 2 (alkene) RC 2 R (acid, ester) Benzene C (aromatic) RCH, R 2 C (aldehyde, ketone) Approximate IR Absorption Frequencies (cm -1 ) Stretching Vibrations --H (alcohol) C=C (alkenes) H (carbox. acid) C= (ald., ketones) R 2 N-H (amine) C= (acyl halides) sp C-H (alkynes) C= (esters) sp 2 C-H (alkenes) C= (amides) sp 3 C-H (alkanes) sp 2 C- (carbonyls) 1200 triple bond (alkynes) sp 3 C- (alcoh., ethers) triple bond (nitriles) Bending Vibrations RCH=CH 2 (alkenes) 910, 990 Monosubstituted benzene , R 2 C=CH 2 (alkenes) 890 ortho-disubstituted benzene R 2 C=CHR (alkenes) meta-disubstituted benzene , para-disubstituted benzene

126 Chemistry 3720, Spring 2015 Exam 2 - Key Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached at the back of the exam. Good Luck! HDI/Unsaturation Number = [#C atoms ½#H atoms ½#Halogen atoms + ½#N atoms] (9 pts) 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. 1

127 2. (20 pts) Provide the expected major products from each step of the following reaction sequences. Be sure to include any stereochemical changes where applicable. a. + H 1. PhMe, reflux 2. Na 2 Cr 2 7, H 2 S 4 1. H + H 2. H + H major (endo) major (exo) b. 1. Br 2, heat 2. KtBu 1. Br m-cpba (+/-) (+/-) c. 1. Zn, HCl H H H 2. Na 2 Cr 2 7, H 2 S 4 Br CN d. 1. HBr 2. NaCN, DMF (+/-) (+/-) e. H 1. HN 3, H 2 S 4 2. Sn, HCl H H N 2 NH 2 2

128 3. (9 pts) 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. a. 6 pi electrons, therefore 4n+2 =6; n =1 integer + flat, fully conjugated = aromatic only bonding M.. are populated b. 6 pi electrons, therefore 4n+2 =6; n =1 integer + flat, fully conjugated = aromatic only bonding M.. are populated c. 4 pi electrons, therefore 4n+2 =4; n =1/2 non-bonding orbitals half full = antiaromatic non-bonding M.. half-populated 4. (9 pts) 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. a. b. c. H H d. H e. f. 1 H NMR (CDCl3) ppm: 1.05 (s, 9H), 5.83 (d, 1H, J = 16 Hz), 6.71 (d, 1H, J = 16 Hz), (m, 5H). 13 C NMR (CDCl3) ppm: 29.5 (q, triple intensity), 32.9 (s), (d), (d, double intensity), (d), (d, double intensity), (s), (d), (s) H H C signal at 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. 3

129 5. (14 pts) 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. CH 3 CCl, AlCl 3 NaBH 4, CH 3 H H IR : 1740 cm -1 [ ] D = 0 PBr 3 D D 2 MgBr Mg, ether Br 1 H NMR: 0.98, 3H d C 8 H 9 MgBr MS: M + = 184, M+2 = 186 Cl, AlCl 3 D D Zn, HCl Final product: Molecular formula = C 13 H 19 D H H 13 C NMR: 9 signals 6. (8 pts) 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. 4

130 7. (14 pts) An unknown organic compound has the molecular formula C 13 H 18 2 ; the mass spectrum shows M+ = 206 a.m.u., the IR spectrum shows significant signals at 1720, 1200, and 800 cm -1, and the 1 H and 13 C 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 1 H NMR spectrum. 1 H NMR (CDCl 3 ) 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). 13 C NMR (CDCl 3 ) ppm : 13.6 (q), 17.4 (t), 22.0 (q, double intensity), 40.4 (t), 75.8 (d), (d, double intensity), (d, double intensity), (s), (s), (s)

131 8. (9 pts) 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 pts) Which of the following diene compounds do you expect to participate in Diels-Alder reactions and which will not? Explain your choices. a. Will react in Diels-Alder reactions since the diene is conjugated and trapped in the required s-cis conformation. b. Will not participate in Diels-Alder reactions since the diene, even though conjugated, is trapped in the s-trans orientation. c. Will not participate in Diels-Alder reactions since the diene is not conjugated; the alkenes are isolated. d. Will participate in Diels-Alder reactions since the diene is both conjugated and can rotate to the required s-cis conformation. 6

132 Chemistry 3720, Spring 2015 Exam 3 Student Name: Y Number: This exam is worth 100 points out of a total of 700 points for Chemistry 3720/3720L. You have 50 minutes to complete the exam. The spectroscopy sheet is attached at the back of the exam. Good Luck! HDI/Unsaturation Number = [#C atoms ½#H atoms ½#Halogen atoms + ½#N atoms] (8 pts) 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? 1