1NAME _______________________ ID # _______________________ ORGANIC CHEMISTRY I (2301) 9:30 – 10:20 am, June 27, 2011 Exam 1 Form A If you want to pick this exam up on Tuesday in class (in public), please check the box on the right: If you do not check the box, I will not bring your exam to class on Tuesday, and you will need to pick up your exam in private from Chemistry department staff in 115 Smith beginning Wednesday, June 29th. Exams that are not picked up within two weeks will be disposed of. A periodic table is attached to the back of this exam as an aid. Otherwise, you are not permitted to use any other materials (including notes, books, or electronic devices of any kind). Right now, write your name at the top of this page, and fill in the bubbles on the back of the multiple-choice answer sheet for your name and your 7-digit student ID number. When the exam begins, please write your name at the top of the next page. You may use pen or pencil. However, re-grades will be considered only for exams completed in pen. Please write your answers in the boxes/spaces provided. If your answer is not in the appropriate space (say, for example, it’s on the back of the page), draw us an arrow and/or note telling us where to look.2Multiple-Choice Section Please answer these problems on the bubble sheet. 1. (3 pts) Which of the structures below is NOT a valid line-angle structure for C3H5NO? a. b. c. d. e. All of the structures (a-d) above are valid. 2. (3 pts) Which of the structures below is NOT a valid Lewis dash-bond structure for C4H9O+? a. b. c. d. e. All of the structures (a-d) above are valid. (3 pts each) For each of the resonance structures below, indicate whether the structure is a major contributor, a minor contributor, or a non-contributor to the overall electronic distribution in the molecule. 3. 4. 5. a. major contributor a. major contributor a. major contributor b. minor contributor b. minor contributor b. minor contributor c. non-contributor c. non-contributor c. non-contributor 6. (3 pts) Each of the C5H10 cycloalkanes below combusts in O2 exothermically (with ΔHcomb << 0) to CO2 and H2O. Which one combusts the most exothermically? a. b. c. d. NOHONHONO CNOHOHH2CONCH3NCH3NCH3CH3H3C CH3H3C CH33Of the molecules listed below, a. b. c. d. 7. (3 pts) Which would be the most acidic? 8. (3 pts) Which would be the least acidic? Of the molecules listed below, a. b. c. d. 9. (3 pts) Which would be the most basic? 10. (3 pts) Which would be the least basic? (2 pts each) In the each of the Lewis structures drawn below: - For each atom marked “hybridization”, indicate whether the atom is hybridized (a) sp, (b) sp2, (c) sp3, or (d) none of these. - For each bond angle marked “angle”, indicate whether the angle is closest to (a) 109.5°, (b) 120°, or (c) 180°. Mark each answer on the bubble sheet, with the problem number indicated inside each box. HCC CHN HNHHCHHCOO HOHOOHNH2NHNH2OOSSangle #15angle #14 hybridization#13 hybridization#12 hybridization #11 angle #19 angle #18hybridization#17 hybridization #164NAME _______________________ Scoring: 19. _________ / 6 21. _________ / 15 20. _________ / 9 22. _________ / 22 Score for this section: _________ / 52 19. (6 pts) On the previous page (in the multiple-choice section), you assigned atom hybridizations and bond-angle values to the two molecules shown below. In the empty boxes below each molecule, draw Lewis wedge/dashed-bond structures that illustrate the most stable three-dimensional structure of the molecule. Draw all atoms, but feel free to omit lone pairs. 20. (9 pts) Draw two more valid resonance structures for methyl isocyanate (at right). Include lone pairs in your resonance structures. Then, draw a consensus structure that illustrates partial charges and bond order in the molecule. HCC CHN HNHHCHHCOO Hwedge/dashed-bond (3D) structure wedge/dashed-bond (3D) structure resonance structure H3CNCOresonance structure consensus structure521. (15 pts) a. For 2-aminobutane (shown at right), draw Newman projections that show the most stable, second-most stable, least stable, and second-least stable conformations of the molecule. Draw your projections looking down the C2-C3 bond, using the perspective I’ve shown in the drawing. b. Next, draw a Lewis wedge/dashed-bond structure for the most stable conformation. Abbreviate carbon atoms as vertices, don’t draw hydrogen atoms bound to carbon, and omit lone pairs. CH3H3CH2NNewman projection for most stable conformation Newman projection for second-most stable conformation wedge/dashed-bond structure for most stable conformation Newman projection for least stable conformation Newman projection for second-least stable conformation6 22. (XX pts) 4-hydroxy-1-methyl piperidine (1) is a base, and it reacts with hydrochloric acid to form two conjugate acid stereoisomers as products. In one of the products, the -OH and -CH3 groups are cis, and in the other product, they are trans. a. Using “electron pushing” (with double-barbed arrows), show how the molecules on the left of the diagram below would react in an acid-base reaction to transfer a proton from one to the other. Draw your arrows directly on my structures. b. In the boxes on the right, draw the two products as wedge/dashed-bond structures. c. For both of these products, the most stable conformation is a chair. In the boxes below, draw the most stable chair conformation of each product. Feel free to omit C-H’s and lone pairs, and abbreviate -CH3 as I have, but draw all other atoms. cis-disubstituted conjugate acid + trans-disubstituted conjugate acid Cl+ Cland HCl+ N CH3HO1 most stable chair conformer for cis-product most stable chair conformer for trans-product7d. Ordinarily, the boat conformation of a six-membered ring is much less stable than its chair conformation. In the case of the trans-disubstituted product on the previous page, this is still true, but the trans-boat conformation does have a stabilizing interaction that the cis-isomer doesn’t. On my incomplete structure on the right, - Add an -OH, a -CH3, and a proton to illustrate the trans-product in its most stable boat conformation; - Then, illustrate and label (with a name) the stabilizing interaction that makes