225Sp04 Test 3 - CHEMISTRY 225 TEST#3 JUNE 4 2004 1(14 2(18 NAME 3(29 GOOD LUCK 4(14 TOTAL Atomic numbers H = 1 C = 6 N = 7 O = 8 S = 16 Cl = 17 Br

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CHEMISTRY 225 T E S T # 3 1. ________ (14) JUNE 4, 2004 2. ________ (18) NAME _______________________________________________ 3. ________ (29) G O O D L U C K ! 4. ________ (14) TOTAL (75) Atomic numbers: H = 1, C = 6, N = 7, O = 8, S = 16, Cl = 17, Br = 35 1. (14 Points) CHIRAL AMINO ACIDS. (-)- Threonine (structure to the right and Test #2) is one of two naturally occurring amino acids (the other is isoleucine) with two stereogenic carbons. a. ( ________ / 6) (4) Determine the absolute configurations at the two stereogenic carbons of (-)-threonine. ( 2 ______ , 3 ______ ) (2) Would you expect the enantiomer of (-)-threonine to be dextrorotatory levorotatory optically inactive impossible to determine (circle one). b. ( ________ / 8) (4) Convert (-)-threonine to a Fischer projection with the longest carbon chain vertical. (2) Write a Fischer projection for the enantiomer of (-)-threonine. (2) Write a Fischer projection for a diastereomer of (-)-threonine. enantiomer diastereomer CO 2 H (-)-threonine NH 2 OH H CH 3 2 H H (-)- threonine (CH 3 CHCHCO 2 H) OH 2
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2 2. (18 Points) STEREOCHEMISTRY IN ORGANIC REACTIONS. a. ( ________ / 5) A dramatic rate acceleration was observed when the following transformation was carried out with microwave irradiation [ Tetrahedron Lett . 2004 , 45 , 4149]. CH 3 O N 3 C OO H CCH 2 CHCH 2 2 2 2 2 2 3 HO H Stereochemical representation of product (3) Write a structure for the product that shows its stereochemistry clearly. (2) Directly on the structure of the reactant, write in a pair of diastereotopic hydrogens. Label these as H a and H b . b. ( ________ / 3) Chemists in Hong Kong have recently described a method for converting an aromatic aldehyde to an alcohol with three additional carbons [ Tetrahedron Lett. 2004 , 45 , 4189]. An example of this transformation is shown below. CHO + BrCH 2 CH=CH 2 CHCH 2 OH 2 Fe NaF(aq) Determine the stereochemical composition of the product of the reaction.
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This note was uploaded on 09/12/2011 for the course NATURAL SC 225 taught by Professor Marician during the Spring '11 term at University of Michigan-Dearborn.

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225Sp04 Test 3 - CHEMISTRY 225 TEST#3 JUNE 4 2004 1(14 2(18 NAME 3(29 GOOD LUCK 4(14 TOTAL Atomic numbers H = 1 C = 6 N = 7 O = 8 S = 16 Cl = 17 Br

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