UCSC, Binder (First and Last) CHEM 8A, Organic Chemistry I Summer 18 FINAL EXAM (400 points) 1 (60)

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1 UCSC, Binder Name (First and Last) CEM 8A, rganic Chemistry I Summer 18 FINAL EXAM (400 points) 1 (60) 2 (65) 3 (60) 4 (70) 5 (75) 6 (70) Total (400) % In each of the following problems, use your knowledge of organic chemistry conventions to answer the questions in the proper manner. Be sure to read each question carefully. You will have the entire class period to complete this exam (2 hours), but hopefully you won t need it! You are welcome to use pre-built models. Make sure there are 6 pages (6 problems). Please write your last name and first initial on the top of each page once instructed to start the exam. Keep your eyes on your own paper. Electronic devices of any kind are not allowed, including cell phones and calculators. Any student found using any of said devices, or found examining another student s exam, will be promptly removed from the exam room and at minimum will receive a zero on this exam. Such an incident may also be considered a form of academic dishonesty and reported to the UCSC Judiciary Affairs Committee.

2 1. Fundamentals TC, a commonly known psychoactive molecule from cannabis, is not directly synthesized by marijuana plants themselves. TC is formed from TCA through a process called decarboxylation. (a) (15 points) List the 5 functional groups in TCA and give the hybridization of the indicated atoms. Functional Groups in TCA: C 2 ybridization in boxes TCA Tetrahydrocannabinolic acid (b) (25 points) Estimate the pka of the acidic portion of TCA shown below. Add curved arrows to show the deprotonation of TCA with a base. Draw its conjugate base and two non-equivalent resonance structures. (c) (20 points) Decarboxylation begins with the keto-enol tautomerization of TCA, as shown below. A molecule of carbon dioxide is released in the second step. Add curved arrows to explain the movement of electrons from a base to a proton in the tautomerization and decarboxylation of TCA. :Base + C 5 11 Enol-Keto Tautomerization + :Base C 2 Decarboxylation C 5 11 C 5 11 TCA TC (Tetrahydrocannabinol) If you do your reaction book-keeping and understand arrow-pushing, you ll get a high score! 1

3 2. Nomenclature (a) (10 points) Draw two chiral molecules that are diastereomers of each other (no more than six carbons). Assign each chiral center as R or S. (b) (15 points) Draw structures corresponding to the following names. ortho-bromophenol meta-chlorobenzoic acid Z-3-heptene (c) (10 points) Circle the aromatic compounds. B (d) (15 points) Draw the most and least stable conformations of butane. The more stable conformation avoids strain. (fill in the blank) (e) (15 points) Draw the two conformations of 1-tert-butylcyclohexane. Indicate the less stable of the two. The more stable conformation avoids interactions. (fill in the blank) 2

4 3. Single-Step Reactions (60 points) WAT S IN TE BX?!?! Fill in the missing reactant, reagent, or product. If no reaction occurs as written, fill in the box with NR. (a) gs 4, 2 S 4 2 (b) 1. B 3, TF , Na (c) KI DMS (d) (e) (f) 3

5 4. (70 points) Reaction Puzzles Where have you seen these problems before? (a) (25 points) Fill in the missing molecules in the boxes and reagents over the arrows. Mg MgBr (b) (30 points) Fill in the missing molecules in the boxes and reagents over the arrows. (c) (15 points) Draw the product of each substitution reaction. Circle whether it proceeded via S N 1 or S N 2 mechanism. For each starting material, indicate whether the reaction to the left or right is faster by clearly circling the reagents that give a faster reaction. If neither is faster or if there s not enough information to decide, leave that part blank. NaCN (2M) DMS Br NaCN (1M) DMS NaBr (1M) TF Cl NaF (1M) TF C 3 C 2 - (1M) C 3 C 2 - (1M) C 3 C 2 I DCM 4

6 5. (75 points) Mechanisms The reaction of (1S, 2R)-1-bromo-2-methyl cyclohexane with sodium hydroxide gives a complicated mixture of products. Products are observed to have molecular formulas of C 7 14 and C Draw the two expected products and separate mechanisms for each. Na 2 + (1S,2R)-1-bromo-2-methyl cyclohexane C 7 14 C 7 12 (mixture of diasteromers) Mechanism to C 7 14 product (please redraw all starting materials): Mechanism to C 7 12 product (please redraw all starting materials): Bonus question: A slightly unexpected product, also with formula C 7 14, is observed in this reaction as well. This unexpected product is a constitutional isomer of the compound above and occurs due to a rearrangement of the reaction intermediate. Show the full-arrow pushing mechanism and product for this other C 7 14 product. 5

7 6. (70 points) Multi-Step Synthesis Choose any two of the following synthetic problems. Clearly cross out which problems you are skipping with a large X. You may use any alkyl halide or organometallic reagent to introduce new carbons and any other reagents necessary. Show the product after each step. If there is a mixture of products, assume the products are separable so you can move forward with the desired product. No mechanisms or stereochemistry necessary. 6