CHEM 232 Final Exam May 10, 2014 RedID number: Signature: Your lab section and TA name: (if you are not in a lab section write no lab ) Instructions: 1. In fairness to all, do not open this test until everyone has one. 2. Please answer briefly and concisely in the space provided. 3. Put your name, ID number and signature on this page. 4. This test is designed to last from 10:30 am to 12:30 pm. 5. Nothing other than writing implements, a simple calculator, and a model kit are allowed. 6. If you finish early, quietly place the test in the pile corresponding to your lab section or the separate pile for no lab. Points Available: 206 (to be scaled to 300; or 450 if your final replaces a midterm) 1 of 11
1. Fill in the blank boxes to complete these reactions, including stereochemistry where applicable. (16; 2 each) 2. a) Label the hybridization of all non-hydrogen atoms in this molecule. e.g. sp 3 (7) b) Identify the type of orbital (e.g. sp 3 ) housing each of the five unshared pairs, labeling which is which. (5) 2 of 11
3. Provide the IUPAC names for these molecules. Include E/Z and R/S designations, as required to specify stereochemistry. (16; 4 each) 4. Complete this chart, showing the bonded groups on the Newman projections and the relative energy of the conformations for the given bond rotation for this molecule: (15 points) 3 of 11
5. The formula C 6 H 12 has many possible constitutional isomers. The 1 H NMR spectra for two of them are shown below (one is labeled M and the other, N). Using these spectra, determine the structures of M and N and label, as accurately as possible, which NMR peaks correspond to which hydrogen atoms in each molecules. (24 points; 12 each) The signal at 2.0 ppm is a multiplet. The signal at 1.5 ppm is a sextet. 6. How many signals would you expect to see in the 13 C NMR for each of these compounds (i.e. how many unique types of C atoms are present)? (6 points; 3 each) 4 of 11
7.(a) Show all of the initiation and propagation steps of this radical reaction, and show two example termination steps. Label the steps as initiation, propagation, and termination. (15) (b) Explain briefly, with specific reference to your mechanism, the regioselectivity of the reaction (why H and Br end up where they do). (3) Note: (c) and (d) can be answered from general knowledge, even if you missed (a) and (b). (c) Explain briefly why only a small amount of ROOR is used. (3) (d) What two specific checks can you make to help be sure that your propagation steps are correct? (4; 2 each) 5 of 11
8. Using conformational analysis of cyclohexane and showing the complete mechanism, explain which of these two E2 reactions is faster. (12 points; 5 points for just the mechanism) 9. Add the correct stereochemistry to the product and show the complete mechanism for this reaction. Briefly explain your choice of stereochemistry. Provide also the inorganic side product (the? ). (12 points) 10. Explain, drawing the relevant intermolecular interactions, which of these constitutional isomers has greater solubility in water. (6 points) 6 of 11
11. Circle which alcohol is more acidic and draw the appropriate resonance structures needed to explain your choice. You do not have to draw all resonance structures. (8 points) 12. Hydrolysis of alkyl halides is this reaction: This list of compounds is given in decreasing order of the rate of hydrolysis in 20% H 2 O in EtOH (solvent) at 55 C. Briefly explain with reference to mechanisms. (12 points) 13. Predict which of these two products would form in this reaction and explain your choice, showing all of the steps in the mechanism and adding the stereochemistry to the product. (12 points) 7 of 11
14. Show the complete mechanism for this reaction. (10 points) 15. Draw all of the stereoisomers of this compound. Label the relationships between the compounds as enantiomers or diastereomers. Identify the meso compound, if there is one. You do not need to use chair conformations (or any other conformational analysis). (8 points) 16. Propose a synthesis route for the compound shown. Mechanisms are not needed, only the sequence of reactions. It s your choice whether or not to use retrosynthetic analysis (12 points) 8 of 11
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Grading Problem 1 Problem 2 Problem 3 Problem 4 Problem 5 Problem 6 Problem 7 Problem 8 Problem 9 Problem 10 Problem 11 Problem 12 Problem 13 Problem 14 Problem 15 Problem 16 /16 /16 /15 /24 /6 /25 /6 /8 /10 /18 TOTAL /206 (to be scaled to 300; or 450 if your final replaces a midterm) 11 of 11