CHEM 281 - 2011-3 Problem Set 12 - WEEK 13

CHEM 281 - 2011-3 Problem Set 12 - WEEK 13 - Representative...

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2 Representative Past Final Questions 1. Consider the reaction below and answer the following 5-part question (12 marks): 1. a). Provide the IUPAC chemical name for compounds A, B, C and D (use R/S nomenclature where appropriate) (4 marks): A B C D 1. b). Provide a detailed stepwise reaction mechanism (using double-headed “curly arrows”) to account for the formation of compound B from compound A . Note: H 3 PO 4 acts as a proton source in this reaction (3 marks): H 3 C CH 3 CH 3 H 3 C H 3 PO 4 H 3 C CH 3 H 3 C OH H CH 2 H H 3 C H 3 C CH 3 CH 3 CH 2 H 3 C H H 3 CCH 3 ++ B (3%) A D (33%) C (64%) CH 3 H 3 C H H 3 3 E
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3 1. c). Given that the products C and D are formed from the common reaction intermediate E, provide a detailed reaction mechanism (using double-headed “curly arrows”) to account for the formation of compounds C and D from intermediate E (2 marks): Formation of C: Formation of D: 1. d). Explain why there is a greater amount of compound C formed than compound D (1 mark): 1. e). Provide a detailed reaction mechanism (using double-headed “curly arrows”) to account for the formation of intermediate E from compound A . (Hint: carbocation rearrangement) (2 marks):
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4 3. Answer the following 8-part question (10 marks): 3. a). Draw the chemical structure of 4-methylcyclohexanone (1 mark): 3. b). Is 4-methylcyclohexanone a chiral compound (1 mark)? 3. c). The reaction of 4-methylcyclohexanone with sodium borohydride (NaBH 4 ) in methanol affords two products, both of which are alcohols. Please draw the chemical structures of these products (show clearly their stereochemistry) (2 marks): 3. d). What is the stereochemical relationship of the above two products (1 mark)? 3. e). Are either (state which one), neither or both of the above two products chiral (1 mark)? 3. f). When a mixture of the above two products is treated with concentrated sulfuric acid (H 2 SO 4 ) the reaction product is a racemic mixture of two alkenes. Please draw the chemical structures of these products (show clearly their stereochemistry) (2 marks): 3. g). Indicate above which compound has ( R) -stereochemistry (1 mark): 3. h). Treatment of the above racemic mixture of two alkenes with meta -chloroperoxybenzoic acid ( m -CPBA) affords a mixture of epoxides that are stereoisomers of one another. How many stereoisomers are there (1 mark)?
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5 4. Please provide reagents for the following transformations. In certain cases more than one separate reaction is required to convert the starting material to the product indicated (12 marks): O CH 3 H ( R )-1,2-propanediol O 3 H ( S )-1,2-propanediol H 3 C O 3 O H 3 C OH 2x H 3 C 3 O H 3 C 3 OH H 3 C H 3 C 3 OH H 3 C CH 3 OH + H 3 C H 3 C OH 3 3 CH 3 3
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6 5. Please provide the product(s) and major byproduct(s) of the following reactions. Where appropriate indicate the stereochemistry of the reaction products (14 marks): HC H 3 Br H NaSCH 3 Note: Fischer projection formula Br OH Br OH Hint: One of these reactions affords a bicyclic ether and the other affords an alkenol CH 3 H 3 C CH 3 O K CH 3 H 3 C CH 3 O K O OH 1. SOCl 2 2. 2 x NH(CH 3 ) 2 DCl, D 2 O 1. Br 2 , H 2 O 2. NaOH (aq) 3. LiAlH 4 then H 2 O OH OH H - H 2 O O H CH 3 H 3 C
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This note was uploaded on 12/07/2011 for the course CHEM 281 taught by Professor Williams during the Fall '11 term at Simon Fraser.

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CHEM 281 - 2011-3 Problem Set 12 - WEEK 13 - Representative...

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