CHE 230-001, Organic Chemistry I Exam 2, October 19, 2011 Name ______________________ Student ID No. ___________________ Before you begin this exam: First: You are allowed to have pens, pencils, and a simple model set at your seat. Please put away all other materials. Second: Place your student identification on your desk. A proctor will come around to check everyone’s ID. Third: Read through the entire exam. Your goal, as always, is to score as many points as possible. Do not waste time on problems that you can’t do if others that look easy. Fourth: It is critically important that your answers be written in a clear, unambiguous manner. Answers in which your intentions are unclear will not receive credit. Fifth: READ THE INSTRUCTIONS FOR EACH PROBLEM. Once the start time is announced, you have 50 minutes to complete this exam. There will be no extensions, so budget your time carefully. Problem Number Points Possible Score 1. 30 _____________ 2. 14 _____________ 3. 16 _____________ 4. 15 _____________ 5. 20 _____________ 6. 20 _____________ 7. 20 _____________ 8. 25 _____________ 9. 20 _____________ 10. 20 _____________ Total 200 _____________1. a. How many stereoisomers are possible for 2,3-butanediol? b. Draw each stereoisomer. Assign an R or S configuration to each stereocenter. c. Which of your structures are enantiomers and diastereomers? d. Are any of your structures meso? If so, which one(s)? 2. Draw the stereoisomers for 2,4-heptadiene, labeling E and Z in each structure. 3. Assign the relationship between each pair of molecules (constitutional isomers, enantiomers, diastereomers, or the same). a. b. c. d.4. Draw the skeletal structure for each of the following molecules. Do not include implied C or H atoms. Do not show any lone pairs. a. toluene b. anisole c. m-chlorophenol d. p-nitroaniline e. benzaldehyde 5. For each of the structures below, assign whether the molecule is aromatic, antiaromatic, or non-aromatic.6. Draw the skeletal version of the major product of each the following Diels–Alder reaction, including its stereochemistry where appropriate. If more than one major product forms in equal ratios to its stereoisomer, draw only one stereoisomer (in this case, either stereoisomer is acceptable). You may show implied H atoms. Do not show lone pair electrons. Also, state whether you think that reaction a or b would react faster, and explain your reasoning. a. b. 7. Draw the reaction mechanism, reaction conditions, and cationic intermediates leading to both the major kinetic product and the major thermodynamic product for the reaction of the diene shown below with one equivalent of HBr. Label the more stable cationic intermediate. Label the kinetic product and the thermodynamic product. For each C atom, you can show either all H atoms or no H atoms.8. Use the inscribed polygon method to construct a MO energy diagram for the cyclopentadienyl anion and describe its ground-state electron configuration. Be sure to fully label each orbital and describe your results in terms of Huckel’s rule. Is it aromatic or antiaromatic? 9. Use the 1H NMR data to draw structural formulas for the following: a. C4H8Cl2 δ 1.60 (doublet, 3H) δ 2.15 (multiplet, 2H) δ 3.72 (triplet, 2H) δ 4.27 (multiplet, 1H) b. C4H8O δ 1.0 (triplet, 3H) δ 2.1 (single, 3H) δ 2.4 (quartet, 2H)10. Compound C shows a molecular ion at m/z 148 and other prominent peaks at m/z 105 and 77. Below are the infrared and 1H NMR spectra. a. Deduce the structural formula of compound C and draw its structure. b. Draw the structures that cause the peaks at m/z 105 and
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