Test 3 Chemistry 21 - Dr. Kline December 6, 2017

Transcription

1 Test 3 Chemistry 21 - Dr. Kline December 6, 2017 This test consists of a combination of multiple-choice and other questions. There should be twenty questions on eight pages. Do not use your own tables, scratch paper, or other information. A periodic table and other information will be provided. Please turn off all cell phones and other devices that could make noise or vibrate. No food. No gum. Calculator OK. The test will end two hours and 15 minutes after it starts. You may use a template (stencil). No sharing of stencils once the exam starts. Multiple-Choice Questions. These 11 questions are worth three points each, for a total of 33 points. There is only one answer per question unless stated otherwise for a given problem. Answer each question by bubbling in the letter(s) corresponding to the correct choices on the provided answer sheet. If more than one answer is correct, bubble in all of the correct ones. It is not necessary to show work for these questions and, in fact, it will be ignored. You may write on the exam. 1. Which of the following compounds is consistent with the proton NMR spectrum below. a. b. c. d. e. none 2. Which of the following compounds will give a meso compound when reacted with NMO in the presence of catalytic OsO4? More than one answer may be correct. a. b. c. d. none 3. Which of the explicitly drawn C H bonds has the smallest bond dissociation energy? a. b. c. d. e. Test 3A - Fall 2017 Page! 1 of! 8 Page Score

2 4. Each of the propagation reaction steps below is exothermic. Which is more exothermic (has a more negative H value)? The two propagation steps are for different reactions. a. b. c. both have the same H value d. it is impossible to tell 5. What is the major product expected from the reaction below? a. b. c. d. e. It is impossible to predict because both both sides of the double bond are CH 6. Which set of reagents is the most suitable for the following transformation? a. H2O with H2SO4 catalyst b. BH3 THF; then H2O2, NaOH c. H2O with ROOR d. Hg(OAc)2 with water; then NaBH4 e. HBr; then NaOH 7. Which alkene is the best to use in a reaction with HCl to make 3-chlorohexane? a. 1-hexene b. 2-hexene c. 3-hexene 8. Which is the least reactive with HCl? a. b. c. d. it is impossible to tell Test 3A - Fall 2017 Page! 2 of! 8 Page Score

3 9. Which alkene produces the alcohol shown more selectively(*) when reacted with water in the presence of a strong acid catalyst? (*) relatively higher proportion of the desired compound as compared to a regioisomer a. b. c. They react equally selectively because both reactions proceed via the same tertiary carbocation. 10. A compound with the formula C8H16 reacts with bromine to give a pair of enantiomers. When the same compound is reacted with ozone followed by a reductive workup with Me2S, two equivalents of the aldehyde shown are formed. What is the structure of C6H18? a. b. c. d. e. 11. An alkene reacts with water in the presence of a strong acid catalyst to give an alcohol with the proton NMR shown below as the major product. What is the structure of the alkene? a. b. c. d. e. none Test 3A - Fall 2017 Page! 3 of! 8 Page Score

4 Other Questions Each of the following questions is worth the indicated number of points, for a total of 67 points. Please be sure that you provide all of the information requested for each question points Draw the structure of the final major organic product from each of the following reactions or reaction sequences. Please put a box around your final answer in each part. Show stereochemistry if not all stereoisomers are formed. a. b. c. d. e. f. g. Test 3A - Fall 2017 Page! 4 of! 8 Page Score

5 13. 3 points Name the compound below, using one of the naming systems discussed in class. Circle or put a box around your final answer points Each of the spectra below corresponds to one of the compounds given. Match each spectrum with a compound by writing the letter for the compound to the right of the spectrum. Provide a brief justification for each spectrum points. Ozonolysis of a diterpene (ten carbons), followed by reductive workup gives the compounds shown below. Reaction of the diterpene with excess hydrogen over platinum gives a compound with the formula C10H20 that has seven signals in its carbon NMR spectrum. Draw the structure of the diterpene. You do need to have enough work shown to indicate that you didn t just guess. Test 3A - Fall 2017 Page! 5 of! 8 Page Score

6 16. 7 points Write a plausible mechanism for the reaction below. Remember to include curved arrows for electron movement and formal charges points Write a plausible mechanism for the tautomerization reaction below. Remember to include curved arrows for electron movement and formal charges points Why is the reaction below unlikely to produce significant amounts of the product shown? What happens instead? You may describe what happens or draw a structure of it. Test 3A - Fall 2017 Page! 6 of! 8 Page Score

7 points Provide a plausible synthesis for each of the following transformations. Include structures of any intermediate products that could be isolated. a. b. Test 3A - Fall 2017 Page! 7 of! 8 Page Score

8 20. 8 points A compound with the formula C10H12O2 has the spectra below. Draw the structure of the compound and put a box around your final answer. Show work and justification. DEPT-135 information is given above each peak in the carbon NMR. Test 3A - Fall 2017 Page! 8 of! 8 Page Score