Complete organic chemistry 2 exam from 3:30-5:30pm central time on 5/6/21 while scoring at least a 91%
final_exam_f2016_done.pdf Chem 234: Final Exam December 8, 2016 Name: Student ID number: Discussion TA: Discussion day and time: Seat Number: (1) Put your final answer in the box, when provided, to obtain full credit. (2) Please turn off any electronic devices. (3) People caught using electronic devices will have their exams confiscated. GOOD LUCK! Point total: Question 1 (35 pts): Question 2 (35 pts): Question 3 (20 pts): Question 4 (40 pts): Question 5 (30 pts): Question 6 (15 pts): TOTAL POINTS: Out of 175 pts 1 1. (35 points) Predict the products and indicate the relative stereochemistry for the following transformations. When necessary indicate the major product. (a) (5 points) (b) (5 points) (c) (5 points) 1. 2. NaBH3CN, HOAc O H H2N Me Me 1.H3O+, heat 3. H3O+H H Me H Me OMeMe H O O 2. PhMgBr, Et2O 1.Br2, FeBr3 2. BrMg F cat. Pd(PPh3)4, THF OMe OMe 2 (d) (5 points) (e) (5 points) (f) (5 points) 1. NaOMe, HOMe O MeO Et OMeO 2. H3O+, heat 1.NaOMe, HOMe O Me CF3 Br Ph 2. H2N H N MeMeOH, H+ 3. xylenes, heat 1. 2. cat. (Ph3P)3RhCl, H2 CH2Cl2 Me Me toluene, heat CNNC 3 (g) (5 points) 1. LiAlH4, Et2O 4. 2. H3O+ O O 3. PCC, CH2Cl2 Ph3P CH2 , THF 5. PCy3 Ru PCy3 Ph Cl Cl (2 mol %) CH2Cl2 4 2. (35 points) Provide the necessary reagents to accomplish the desired organic reactions. Please number the steps and note that some reactions will require more than one step. (a) (5 points) (b) (6 points) O O O O O OH Me OHMe 5 (c) (6 points) (d) (6 points) OMe OO n OMe OMe O H HN NH3 HN O O 6 (e) (6 points) (f) (6 points) Et Et Et Et CO2Me O Et Me OHO Cl Me 7 3. (20 points) Perform the two retrosynthetic analyses given below. a) (10 points) 1. 2. 3. 8. 6. 7. 4. O O O O Br 5. Ph OCl 8 (b) (10 points) 1. 2. 3. 4. 5. 7. 6. 6. H N O OEt O N O Me OMeOO Ph 9 4. (40 points) Please provide a detailed arrow pushing mechanism for the following transformations. (a) (6 points) O HMe Me H HO OH Me MeH2O 10 (b) (8 points) O Cl OMe O OMe O Mepyridine HO Me 11 (c) (8 points) N H N O OH OH Me O3PO -2 t-Bu N H N OH Me O3PO -2 t-Bu + CO2 amino acid decarboxylase 12 (d) (10 points) O OHHN i-Pr OOPh O OH2N S O O H NN H i-Pr SO O O Ph N • N + 13 (e) (8 points). PCy3 ligand dissociation Cy3P Ru PCy3 Cl [2+2] retro [2+2] Ph olefin coordination olefin coordination Cy3P Ru Cl Ph Cl Cl 14 5. (30 points) Intra- and Intermolecular interactions that control reactivity and structure. (a) (8 points) Consider the following aldol reaction. Fill in the substituents in the lowest energy chair transition state that explain the stereoselectivity in the deprotonation (step 1). EtO Me O 1. LiN(iPr)2, THF, –78 °C 2. PhCHO 3. H4NCl (aq soln) EtO Ph O Me OH O Li H 15 Fill in the substituents in the lowest energy chair transition state that explain the stereoselectivity in the enolate addition to the aldehyde (step 2). O O Li EtO 16 (b) (5 points) Provide the chair transition state for the following acid-catalyzed cyclization. (c) (5 points) Provide the chair transition state to explain the diastereoselectivity in the following Claisen rearrangement. O Me Me Me HO Me H H+ xylenes heat O HPhO Me Me Ph 17 (d) (7 points) Consider the following glycosylation reaction. (a) (3 points) Draw a three-dimensional representation of the oxocarbenium intermediate. (b) (4 points) Illustrate the transition state that leads to: O BnO OAc OAc BnO NaCN, H+ BnO O BnO OAc CN BnO BnO O BnO OAc BnO BnO CN H H + O BnO OAc BnO BnO CN H 18 (e) (5 points) Consider the following nucleotide base pairs. Illustrate the hydrogen-bonding that occurs between two matched base pairs in a double-stranded RNA ladder- structure. N NN N H NH2 N NHN N H NH2 O HN N H O Me O HN N H O O N N H O NH2 19 6. (15 points) Spectroscopy (a) (5 points) Predict the product for the reaction given below. (b) (3 points) For the 1H NMR spectrum illustrated below, label each of the indicated peaks with the appropriate functional group. List of 1H NMR resonances: 9.9 ppm (singlet, 1H), 7.7 ppm (doublet, 2H), 6.9 ppm (doublet, 2H), 3.7 ppm (singlet, 3H). 3. Cl Cl O O , DMSO Et3N, CH2Cl2 MeO 1. PhMgBr, Et2O 2. H3O+ H O 20 (c) (2 points) For the 13C NMR spectrum illustrated below, label each of the indicated peaks with the appropriate functional group. List of 13C NMR resonances: 190 ppm, 164 ppm, 132 ppm, 130 ppm, 114 ppm, 55 ppm. 21 (d) (2 points) For the IR spectrum illustrated below, label each of the indicated peaks with the appropriate functional group. (e) (2 points) Draw the structure of the compound represented by the spectra given above in the box given below. (f) (1 point) Which reaction failed in the three-step sequence? The spectra for this problem were reproduced from the National Institute of Advanced Industrial Science and Technology, http://riodb01.ibase.aist.go.jp/sdbs/ on December 7, 2015. 22