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Exam 3 -- Fall 2007 -- Blank

Exam 3 -- Fall 2007 -- Blank - Name Page 1 F.07.210e3pl...

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Unformatted text preview: Name Page 1 F.07.210e3pl I. (28 points) (a) A clever Chem 21 1 student decided to try and carry out the following transformation in order to impress Dr. Nolta! 1) UPI Compound N Unfortunately, the reaction failed completely! In a few words, tell the student what the major error was in this plan. (b) What is the IUPAC name for Compound N? 6 (0) Compound N can actually be prepared from the corresponding alkene, in a two step sequence. Draw the result of the bromination reaction (if racemic, draw one enantiomer and write "plus enantiomer," if meso, draw it and write "meso," if diastereomers, draw one and write "plus diastereomer(s)," and if there is only one compound with no stereoisomers, then just draw it). Complete the reaction scheme as required. Brz H a a GHQ H CC14 6 (d) Complete the following. In the second step, a reagent that is the direct analogy of OsO4 is used; predict and draw out its Lewis structure as your answer. 4 racemlc Name Page 2 F.07.21063p2 II. (29 points) A. (a) The following electrophilic addition reaction is highly regioselective. Draw the expected product(s) (if racemic, draw one enantiomer and write "plus enantiomer," if meso, draw it and write "meso," if diastereomers, draw one and write "plus diastereomer(s)," and if there is only one compound with no stereoisomers, then just draw it). Note: "D" is deuterium (2H). CH OCH 3\ / 3 CH3OH C — C —> catalytic D CHZPh H2804 _ Compound M . (b) Provide a complete, step—wise mechanisn for this transformation. You should use H—B for any general Bronsted acid that you need, and B9 as its conjugate base. CH3 OCH3 7 7 7 \ _ / C—C / \ D CHZPh F (C) If BrCHZCD3 is named 2—bromo-1,l,l—trideuterioethane, and if (CH3O)2CH2 is named dimethoxymethane, then what is the complete name for Compound M? III. (35 points) A. Interestingly, the reaction between thiols (RSH) and certain alkenes, with no solvent or catalyst present, gives an anti—Markovnikov addition outcome (Tet Lett 2007 48, 8815). Name Page 3 F.07 210e3p3 (a) Predict the structure of the anti-Markovnikov addition reaction product. If racemic, draw one enantiomer and write "plus enantiomer," if meso, draw it and write "meso," if diastereomers, draw one and write "plus diastereomer(s)," and if there is only one compound with no stereoisomers, then just draw it. 0 CHZSH [J + O —> CompoundE Compound D Compound F (b) In contrast, cyclohexene (Compound F) does NOT react with Compound E under exactly the same experimental conditions. The authors propose that an intermolecular interaction between Compounds D and E occurs, which explains the difference. Draw the proposed intermolecular interaction between l draw the proposed intermolecular interaction between Compounds D and E [T Compounds D and E. B. Complete the following reaction schemes by providing the major organic product(s). (a) C1 CH3 (CH3)3COK | CH3 C1(H{0H H H «HthOH ” 3 OCH3 __ + 5 (gives 2 + (CH3)3COH I diastereomers) 5 (CH3)2S four , NOTE - All Manswers L should be drawn in chair Please note that forms, following clearly chair form , following from the one model the model 5 own, are compound that is shown. specifically directed. This 5 ‘ 5 830 - no one mentionecIlI it explicitly avoids debates about "half-chairs," et "-5"once for pla ar forms 1) excess 03 CH3 l / H\C%C\H C / HZC \\ / l C—C’H —* H2C\ / \ /CH3 2) excess Zn H2 / \ H H show all organic products IV. (25 points) Name Page 4 F.07.210e3p4 The major E2 reaction product from the following reaction is an oxygen-substituted alkene (7ft Lett 2006 48, 8353). (a) Predict the structure of this major alkene product, and clearly indicate its stereochemistry. O CH H3C\ // C i E) //S\o H H3\/C—O (9 O CH3 K Ph Fl 0 O (b) Provide the single Newman projection for the conformation of the starting material that leads to the fastest E2 reaction, and therefore to the predicted product. The carbon atom with the leaving should be in the front, and the carbon atom with the 6—H should be in the back. B. 4 In the following reaction scheme, Compound U is protonated to give Intermediate V, which in turn undergoes a fast intramolecular substitution reaction where the sulfur nucleophile ends up forming a cationic, three-membered ring called an episulfonium ion (Intermediate W). The episulfonium ion then undergoes a second intramolecular substitution reaction to give Intermediate X, which is finally, in the last step, deprotonated to give the observed product, Y. Based on this information, draw structures for Intermediates V, W, and X. NO mechanisms are required. acid Name Page 5 F.07.210e3p5 V. (23 points) Complete the following reaction schemes. (a) NH2 Compound R / N “It > OH K N 1) BH3 N 0 2) HZOZ/NaOH O><O 1) SOZCI 5 CH3 in pyridine 2) C43 (9 O O N(CH3)4 O—lr—O—F—O OH OH Compound S NOTE 1: there is a 1:1 ratio between the diphosphate dianion (S) and Compound R. ® NOTE 2: the pKa of the fully 9 . + (CH3)4N OTs I? protonated S 1s 2 O?) OH —> —> H2804 ‘ OH F F (:6le C6H120 H-NMR: 1 signal C—NMR: 2 signals H-NMR: 2 signals (3:1) C—NMR: 4 signals reacts with O3 does not react with O3 ...
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