Exam (6 pts) Show which starting materials are used to produce the following Diels-Alder products:

Transcription

1 Exam 1 Name CHEM (18 pts) Complete the following chemical reactions showing all major organic products; illustrate proper stereochemistry where appropriate. If no reaction occurs, indicate NR : 2. (6 pts) Show which starting materials are used to produce the following Diels-Alder products:

2 3. (8 pts) Name the following compounds using IUPAC conventions: 4. (6 pts) Propose a mechanism for the addition of HBr to 1,3-hexadiene. Show the intermediates that lead to each product and indicate which is more stable. Indicate which product is thermodynamically favored and which is kinetically favored. 5. (8 pts) Draw all reasonable resonance structures for each species. Circle the structure which is the strongest contributor/most stable resonance structure. a. b. c. d. 6. (4 pts) Rank the following dienes in order of increasing heat of hydrogenation (1 lowest to 4 highest):

3 7. (8 pts) (8 pts) For each of the following compounds, indicate the number of resonances (not multiplicities) that would be observed on a 1 H NMR spectrum: Br NH 8. (8 pts) For each of the following compounds, indicate the multiplicity of the resonance observed for the indicated protons (shown Hs): H CH 2 C H 2 CH 3 9. (6 pts) For each of the following molecules circle each set of magnetically unique protons. For each set indicate the approximate chemical shift: 10. (18 pts) Give the structure that would produce each of the following three 1 H NMR spectra. Circle your final answer for grading. a.) C 7 H 5 2 Br There is a 1 H broad singlet at 12 ppm. The resonances below from left to right are a singlet, doublet, doublet and triplet. All resonances integrate to 1H.

4 b.) C 5 H 10. Eyeball measure integrals yourself! Region from ppm is expanded for you. c.) C 5 H 8 2H 3H 1H 2H Score /100 Approx. Course Grade:

5 Exam 1 Name CHEM (18 pts) Complete the following chemical reactions showing all major organic products; illustrate proper stereochemistry where appropriate. If no reaction occurs, indicate NR : No reaction, not a conjugated diene major 2. (6 pts) Show which starting materials are used to produce the following Diels-Alder products:

6 3. (8 pts) Name the following compounds using IUPAC conventions: 2-iodoaniline 2,4-octadiene 4-bromo-2-ethyl-1- flouorobenzene 3-chlorobenzoic acid 4. (6 pts) Propose a mechanism for the addition of HBr to 1,3-hexadiene. Show the intermediates that lead to each product and indicate which is more stable. Indicate which product is thermodynamically favored and which is kinetically favored. 5. (8 pts) Draw all reasonable resonance structures for each species. Circle the structure which is the strongest contributor/most stable resonance structure. a. b. c. d. 6. (4 pts) Rank the following dienes in order of increasing heat of hydrogenation (1 lowest to 4 highest):

7 7. (8 pts) (8 pts) For each of the following compounds, indicate the number of resonances (not multiplicities) that would be observed on a 1 H NMR spectrum: Br NH (8 pts) For each of the following compounds, indicate the multiplicity of the resonance observed for the indicated protons (shown Hs): H CH 2 C H 2 CH 3 doublet quintet quartet doublet 9. (6 pts) For each of the following molecules circle each set of magnetically unique protons. For each set indicate the approximate chemical shift: Aldehyde 9.5, two aromatics , two aliphatics 2.0 and aliphatics 1-2, 2 alkene , H from acid > 10 Terminal alkyne 3.0, 2 aliphatics 2.0 and (18 pts) Give the structure that would produce each of the following three 1 H NMR spectra. Circle your final answer for grading. a.) C 7 H 5 2 Br There is a 1 H broad singlet at 12 ppm. The resonances below from left to right are a singlet, doublet, doublet and triplet. All resonances integrate to 1H. meta substituted, acid proton at 12 m-bromobenzoic acid

8 b.) C 5 H 10. Eyeball measure integrals yourself! Region from ppm is expanded for you. HDI = 1 with an oxygen, suspect C=. n one side a methyl (3H singlet at 2.0), on the other an isopropyl group (septet at 2.4 and doublet at 1.1) c.) C 5 H 8 2H 3H 1H 2H Alkene and aliphatic, HDI = 2 so alkene + another db or ring. Score /100 Approx. Course Grade:

9 Exam 2 Name CHEM (36 pts) Complete the following chemical reactions showing all major organic products; illustrate proper stereochemistry where appropriate. If no reaction occurs, indicate NR : a. b. c. d. e. f. g. h. i. j. k.

10 2. (8 pts) Consider the following substituted benzenes. For each example: a. Indicate whether the substituent is activating or deactivating (circle one) b. Indicate whether it would be ortho, meta or para directing (circle all that apply) rtho Meta Para rtho Meta Para rtho Meta Para rtho Meta Para 3. (6 pts) Nomenclature: Name the acids or provide a structure given the name. a. b. c. d. Succinic acid Potassium 2,3,5-trifluorohexanoate 4. (4 pts) In preparing for this exam you may have consumed caffeine, which inhibits the retention of short term memories (like organic exam chemistry knowledge). Is caffeine aromatic? State your reasoning. 5. (6 pts) Show how the following compound can be synthesized from the indicated starting material: 6. (8 pts) Show the contributing resonance structures following a para addition of an electrophile (E + ) to phenol. Circle the most stable resonance structure or structures.

11 7. (6 pts) We studied the EAS reaction of benzene. There are many other families of aromatic compounds that also undergo EAS reactions. Suggest the probable course of the EAS reactions of thiophene (right). a. Is the ring more or less electron rich than benzene? b. Would EAS reactions be faster or slower? c. What orientation of EAS would be most favored relative to the ring sulfur? Explain why. d. Draw the orbital diagram for thiophene; be sure to label all orbitals containing delocalized electrons and lone pairs. 8. (12 pts) Indicate if the anions would deprotonate the acid in each pair (Circle yes/no): g. h. i. Yes No Yes No Yes No a. b. c. Yes No Yes No Yes No d. e. f. Yes No Yes No Yes No 9. (6 pts) Synthesize m-methoxybenzyl cyanide from m-methylanisole: 10. (8 pts) Circle the compounds that are aromatic; for those that are not aromatic, briefly state which of the four criteria are not met. Approximate Course Grade: A A- B+ B B- C+ C D F Score /100

12 Exam 2 Name CHEM (36 pts) Complete the following chemical reactions showing all major organic products; illustrate proper stereochemistry where appropriate. If no reaction occurs, indicate NR : a. b. NR Friedel-Crafts conditions react with NH 2 c. d. e. f. g. h. i. j. k.

13 2. (8 pts) Consider the following substituted benzenes. For each example: a. Indicate whether the substituent is activating or deactivating (circle one) b. Indicate whether it would be ortho, meta or para directing (circle all that apply) rtho Meta Para rtho Meta Para rtho Meta Para rtho Meta Para 3. (6 pts) Nomenclature: Name the acids or provide a structure given the name. a. b. c. d. Succinic acid Potassium 2,3,5-trifluorohexanoate 4. (4 pts) In preparing for this exam you may have consumed caffeine, which inhibits the retention of short term memories (like organic exam chemistry knowledge). Is caffeine aromatic? State your reasoning. All atoms in both the 6 and 5 membered ring are (or can) be sp2 hybridized. Planar, cyclic 10 pi electrons 2 nitrogens in 6-membered ring with lone pairs, double bond bridging rings, C=N double bond in 5-membered ring and lone pair on N in 5-membered ring. Aromatic! 5. (6 pts) Show how the following compound can be synthesized from the indicated starting material: 6. (8 pts) Show the contributing resonance structures following a para addition of an electrophile (E + ) to phenol. Circle the most stable resonance structure or structures.

14 7. (6 pts) We studied the EAS reaction of benzene. There are many other families of aromatic compounds that also undergo EAS reactions. Suggest the probable course of the EAS reactions of thiophene (right). a. Is the ring more or less electron rich than benzene? b. Would EAS reactions be faster or slower? c. What orientation of EAS would be most favored relative to the ring sulfur? Explain why. d. Draw the orbital diagram for thiophene; be sure to label all orbitals containing delocalized electrons and lone pairs. a. Ring is more e- rich 6 p electrons for 5 atoms vs. 6 for 6 in benzene. b. EAS is faster for more e- rich systems c. rtho (2-) addition additional resonance structure with sulfur Each p-orbital on C has one e-, on sulfur it has two; second lone pair on sulfur in sp 2 orbital 8. (12 pts) Indicate if the anions would deprotonate the acid in each pair (Circle yes/no): g. h. i. Yes No Yes No Yes No a. b. c. Yes No Yes No Yes No d. e. f. Yes No Yes No Yes No 9. (6 pts) Synthesize m-methoxybenzyl cyanide from m-methylanisole: 10. (8 pts) Circle the compounds that are aromatic; for those that are not aromatic, briefly state which of the four criteria are not met. Approximate Course Grade: A A- B+ B B- C+ C D F Score /100