1 CHE 230-002 Organic Chemistry Exam 3, Fall 2011 Name ________________________________ Student ID No. ___________________ Before you begin this exam: First: You are allowed to have writing utensils 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 there are others that look easy. Fourth: Read each question carefully. Be sure you answer the question that is asked. If you erase something, make sure it is very clear what is on erased and what you intend to include in your answer. Fifth: Once the start time is announced, you will have one hour to complete this exam. There will be no extensions, so budget your time carefully. Problem Number Points Possible Score 1. 10 _____________ 2. 30 _____________ 3. 10 _____________ 4. 15 _____________ 5. 20 _____________ 6. 15 _____________ 7. 15 _____________ 8. 15 _____________ 9. 10 _____________ 10. 30 _____________ 11. 30 _____________ Total 200 _____________2 1. (10 points) In the boxes provided below, draw the resonance hybrid for each of the structures below. Don’t forget to show lone pairs and partial charges where appropriate. Circle the sp2-hybridized atoms in the structures provided (not in your hybrid). 2. (30 points) Identify the number of peaks in the 1H and 13C NMR spectra for the following molecules. 3. (10 points) Fill in the blank for the following acid/base equilibrium reaction between phenol and cyclohexanol. The molecule with the most acidic proton is phenol. The equilibrium lies to the left. The most important phenomenon contributing to the pKa difference between the two molecules is resonance. OO!+!-!-!-ClOO1H NMR13C NMR334453OOH+OHO+3 4. (15 points) In each molecule drawn below, circle the most acidic proton. In some cases, there may be more than one equivalent answer, but if so, you only need to circle one H. Bonus: 5 points! Circle the most acidic protons in the molecule below, and briefly state the reason for your choice within the box provided. 5. (20 points) In the box provided, draw the skeletal structures for the products (organic and inorganic) of the following reaction by following the curved arrows. H2CH2CHCCH2CH2CHCHCCHCCHHCNH2OHH2CHCHOCH3HCCCH3H3CH2CCH2CCHOHOCOCH3CH2CH3COThe protons I've circled in the molecule to the left are more acidic because:BONUS!there is greater resonance stabilizationin the resultant anion than in in anion that results from deprotonation of themethyl groupCHHHCl+HCl4 6. (15 points) Given the reaction energy diagram below: Insert the appropriate letters for each of the following: (1) the transition state for the slowest step in the reaction: B (2) the product of the reaction: G (3) the most stable reaction intermediate: C 7. (15 points) In the box provided below, draw the transition state for the each of the following reactions. –OH++HBr+BrH–+CH3BrCH3OHBr–+HHHOHBr!-!-HBr!+!-5 8. (15 points) In each series below, circle the following: a) the molecule that is most reactive in an SN1 reaction: b) the anion that is most reactive as a nucleophile: CH3– –OH –NH2 F– c) the best leaving group: Br– Cl– I– F– 9. (10 points) When 3-chloro-3-methylpentane is treated with a variety of strong bases, the products always contain two isomers A and B with chemical formula C6H12. The 13C NMR spectrum of isomer A has 4 peaks, and the 13C NMR of isomer B has 6 peaks. Draw the skeletal structures of products A and B of this elimination reaction in the boxes below. BrBrBrBrClbaseorproduct A: C6H12 with 4 peaks in its 13C NMR spectrumproduct B: C6H12 with 6 peaks in its 13C NMR spectrum6 10. (30 points) Draw the skeletal structure of the organic product(s) of the following substitution reactions, indicating stereochemistry where relevant. If more than one major product is formed, draw both isomers. an SN2 reaction: an SN1 reaction: an SN2 reaction: ClNaCN+CNBrH2O+OH+OHBrS+S7 11. (30 points) For each set of spectral data below, draw the skeletal structure of the molecule consistent with the data in the box provided. C5H10O2 IR peak at 1740 cm−1 1H NMR (ppm): 1.15 (triplet, 3 H); 1.25 (triplet, 3 H); 2.30 (quartet, 2 H); 4.72 (quartet, 2 H) C6H14O IR peak at 3000–2850 cm−1 1H NMR: 1.10 ppm (doublet); 3.60 ppm (septet) C4H8 Br2 IR peak at 3000–2850 cm−1 1H NMR: 1.87 ppm (singlet, 6 H); 3.86 ppm (singlet, 2 H) END OF EXAM
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