Chem 210- W07exam3Key

Chem 210- W07exam3Key - I. (25 points) Name...

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Unformatted text preview: I. (25 points) Name _______________________ Page 1 Complete the following reactions as directed. Transformations requiring sequential experimental steps should be numbered appropriately. Show the major organic product(s) unless otherwise specified. Abbreviations for reagents are not allowed. If a product forms as a stereoisomeric mixture, draw one and write "+enantiomer" or "+diastereomer" in the box. NOTE: all stereocenters should be drawn unambiguously - show the positions of all atoms or groups at each of these sites. A. Describe the product(s): CH2CH3 OH CH3 H2O H2SO4 (cat) CH3 (check the best answer - no partial credit) H2 Pt CH3 x + diastereomer A single unique product would form A racemic mixture of products would form A mixture of 2 diastereomeric products would form A mixture of 4 stereoisomeric products would form Both regioisomers and stereoisomers would form 3 4 B. CH3 + enantiomer 1. B2H6 2. NaOH/H2O2 OH CH3 H 4 Draw ALL organic products in the appropriate boxes: O H C H H 1H-NMR 13C-NMR C. C7H6 O H2 Pd/BaSO4 PbO 1. O3 2. CH3SCH3 H O signals: 2 (3:1) signals: 2 H + 3 4 H C O 1H-NMR 13C-NMR C O H signals: 1 signals:1 O C H D. OH 3 OsO4 OH H H stereo connectivity H H + diastereomer 4 II. (25 points) Name _______________________ Page 2 Predict the product(s) in each of the following reactions. Draw all products, etc. that fulfill the requirements given in the answer box; be sure to show any stereochemistry clearly. (no partial) A. OH H3C H H product(s) having molecular formula C7H13Br HBr H3C H H Br H3C H Br H H3C Br Br can be drawn flat, too H3C 4 B. O product(s) having the following spectroscopic data: H 13C-NMR 1H-NMR C H3C O O signals: 4 signals: 3 (1:2:3) H H O 4 C. O product(s) having molecular formula C6H10O CH2CH3 Br O CH3CH2OH 78C O CH2CH3 CH3 C H O H C CH3 4 D. ICl reacts with the same stereoselection and regioselection that is seen with reagents like HOBr. (a) draw the intermediate(s) for this reaction (b) draw the final product(s): C5H8ICl CH3 C C H H C CH3 I Cl 1 equivalent I H 3C C C CH2CH3 H3C I C C C H H CH3 H3C C C I Cl a source of electrophilic iodine Cl C H H CH3 3 4 product(s) having molecular formula C7H12 Optically active product(s) Cl H CH3 Optically inactive product(s) CH3CH2ONa CH3CH2OH H CH3 3 3 III. (32 points) Name _______________________ Page 3 Explore the reactivity of Compound A in the following reactions. Show the major organic product(s) unless otherwise specified. If a product forms as a stereoisomeric mixture, draw one and write "+enantiomer" or "+diastereomer" in the box. (a) (b) O OCH3 CH3 CH3 1) H3C H3C C OK H3C 1) O OH CH3 CH3 Cl S CH3 O O S CH3 O HN(CH3)3 Cl CN CH3 CH3 N(CH3)3 K H3C KI 2) CH3I 2) KCN H3C C OH H3C 4 Compound A 4 (c) Provide the complete IUPAC name, including stereochemistry where appropriate, for Compound A. 2 pts/error 1 is unecessary (1R)-2,2-dimethyl-1-cyclobutanol or cyclobutan-1-ol 6 (d) When Compound A is heated under acidic conditions, 2 structurally isomeric (C6H10) fully substituted E1 products are produced. Each product is explained with one rearrangement step that directly leads to a more stable carbocation intermediate. Show the curved arrow mechanism for the formation of the initial carbocation intermediate, then follow the two different rearrangements that lead to the structurally isomeric products indicated by the spectroscopic data. (i) provide the curved arrow mechanism for the formation of the carbocation intermediate shown O H CH3 CH3 H H O H H 2pts each, mechanisms and intermed. O H CH3 CH3 CH3 CH3 6 (ii) Rearrangement 1 - be careful that your rearrangement mechanism leads to the product described final E1 product CH3 13C-NMR signals: 3 CH3 CH3 CH3 provide the curved arrow(s) for the carbocation rearrangement and draw the product of this rearrangment CH3 CH3 3 final E1 product 13C-NMR 3 signals: 4 (iii) Rearrangement 2 - be careful that your rearrangement mechanism leads to the product described CH3 CH3 CH3 provide the curved arrow(s) for the carbocation rearrangement and draw the product of this rearrangment CH3 CH3 CH3 3 3 IV. (26 points) A. N-bromosuccinimide, NBS, is a good source of electrophilic bromine. When used with special reagents that are a source of nucleophilic fluoride, bromofluorinated addition products can be obtained in high yield. In the following observed reaction, two major products are obtained. Based on these observed products, the stereoselection and regioselection for this reagent mixture are identical to those predicted for other halogenation reagents, like HOBr, etc. (b) the other major product (a) C14H12 starting alkene (check all that apply): Name _______________________ Page 4 O Ph N Br O (NBS) Br H C H C F is a regioisomer of the product shown is a diastereomer of the product shown Ph X is an enantiomer of the product shown is formed in a lesser amount than the product shown F (special source of nucleophilic F) X Compound B one of the major products is formed in an equal amount to the product shown is formed in an greater amount than the product shown 4 3 (c) Show a transition state drawing for the last step in the above reaction, where a nucleophilic attack by fluoride leads specifically to the formation of Compound B. Be careful to show stereochemistry as needed. H Ph F Br H Ph 5 (d) Provide the complete IUPAC name, including stereochemistry where appropriate, for Compound B. 2 pts/error (1S,2R)-1-bromo-2-fluoro-1,2-diphenylethane numbering would be the same from opposite side, br alphabetically 6 preferred B. When Compound B is treated with a strong base, bimolecular elimination leads to the formation of a single, kinetically favored alkene product with molecular formula C14H11F. Br H C H F C H3C H3C C OK H3C (a) Draw the kinetically favored E2 product. C14H11F Ph H Ph (b) Draw the Newman projection for the conformation of the starting material that leads to the product you have shown - the carbon with the leaving group should be in front. Br Ph F F Ph H H Compound B 4 4 V. (32 points) Name _______________________ Page 5 Reaction analysis: provide the requested information in each of the following chemical transformations. Show all products unless otherwise indicated, and if any reaction results in a stereoisomeric mixture, draw one and indicate "+ enantiomer" or "+ diastereomer" in the box. A. H3CO CH3 Cl Cl H3C OCH3 CH3 CH3 Cl2, CH3OH 1. LiH LiBr CH2SH 2. CH3CH2Br CH2SH CH2SH Cl and OCH3 must be opposite sides of the ring CH2SCH2CH3 Show ALL final products + diastereomer 4 O O 4 B. NaOCH3 C OH C O CH3OH Na 4 C. 1. BH3 or B2H6 or 9BBN CH3 1. OH CH3 O Cl S O CH3 N CN CH3 2.H2O2 H2O NaOH 4 one of 2 products 2. KCN 4 D. CH3 H C Draw uncharged product(s) CH3OH Br Br CH3 H C OCH3 Cl + enantiomer 4 E. C 1. NaNH2 C C C Na, NH3(liq) C OCH2CH3 C H H 2. CH3CH2I OH NH3 4 NaI OCH2CH3 4 ...
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