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CHEM 2061 – Fall 2008 – EXAM #3 Name ______________________ 1. (12 pts, 4 each) A) Give the structure of the major organic product in each of the following SUBSTITUTION reactions, and B) predict whether the mechanism will be predominantly 1st order (SN1) or second order (SN2). Be sure to show the correct stereochemistry of the product when necessary. If the product is a racemic mixture, draw both enantiomers. H a) HO- Br CH3 H3C OTs CH3CH2OH b) c) H C C CH2Cl CH3CH _ Li+ CH3 2. (10pts, 5 each) A) Give the structure of the major organic product in each of the following elimination reactions, and B) predict whether the mechanism will be predominantly first order (E1) or second order (E2). BE SURE TO SHOW THE CORRECT STEREOCHEMISTRY OF THE PRODUCT WHEN NECESSARY. a) CH3OH CH3CH2 CH3 Br b) Br CH3 CH2CH3 H CH3 H3C C O K+ CH3 CH3 3. (3 pts) Which of the following is the best solvent for a SN1 reaction? a) hexane b) methanol c) acetone d) dichloromethane 4. (8 pts) Write the complete mechanism for the following acid-catalyzed hydration reaction of 2methylpropene. OH H3C H H2SO4 C C H3C C CH3 H3C H H20 CH3 5. (4 pts) Give the IUPAC name of the following compound. Be sure to use E-Z and R-S nomenclature if necessary. CH3 H3 C H 6. (5 pts) Give the major product of the following reaction: CH3 H3C C O CH3 OTs 7. (6 pts, 3 each) Will the following reactions go faster if the concentration of the nucleophile is increased? (Write “Yes” if the reaction will go faster, “No” if it doesn’t go faster). a) H MeO Br H H3C O + b) Br CH3 O O CH3 + H3 C O CH3 O 8. (12 pts) Consider the following E2 elimination reactions of menthyl chloride and neomenthyl chloride: A) Using mechanistic reasoning, EXPLAIN WHY menthyl chloride gives only 2-menthene as its E2 elimination product. B) Explain why 3-menthene (rather than 2- menthene) is the major product in the E2 elimination of neomenthyl chloride. H H3C CH3 Cl CH3 CH2 O CH3 H3C CH3 CH3 H 2-menthene (100% yield) menthyl chloride H H3C CH3 H Cl CH3 CH2 O CH3 H3C CH3 CH3 neomenthyl chloride 3-menthene (78% yield) + 2-menthene (22% yield) 9. (12 pts) Bromoetherification, the addition of the elements Br and OR to a double bond, is a common method for constructing rings containing oxygen atoms. Draw a stepwise mechanism for the following INTRAMOLECULAR bromoetherification reaction. Hint: the mechanism is analogous to that of bromohydrin formation – when Br and OH are added to an alkene double bond using Br2 and H2O). Br2 O Br + HBr HO 10. (28 pts, 4 each) Give the structure of the major organic product of each of the following reactions. Clearly indicate stereochemistry where appropriate. If the major product is a pair of enantiomers, only draw one of the two structures. conc. a) H2SO4 OH heat b) CH3 Br2 CCl4 c) CH2CH3 CH2CH3 H2 Pt d) H3C H CH2CH3 1) O3 CH2CH3 2) CH3SCH3 3) H30+ OsO4 e) H2O2 CH3 1) BH3.THF f) 2) H2O2, NaOH H2O O Cl O O g) CH2Cl2 H