ExamIV_Fall2007_key - Fall 2007 Dr. Marcotte EXAM IV CH339K...

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1 Fall 2007 EXAM IV Name:__________________ Dr. Marcotte CH339K UT EID: ________________ ** SHOW WORK FOR COMPUTATIONAL PROBLEMS OR NO CREDIT!! ** R = 8.314 J/mol . K; F (Faraday constant) = 96,480 J/V . mol 5pt (1) Trans fatty acids, produced by industrial hydrogenation during the manufacture of margarine, Crisco, etc., have been implicated in increased rates of coronary artery disease. Elaidic acid is one such trans unsaturated fatty acid often found in partially hydrogenated vegetable oils. Its shorthand name is 18:1( Δ 9 ). Draw the chemical structure of elaidic acid, making sure to indicate the proper configuration of the unsaturated bond, and number all carbon atoms in the standard way. 17 15 13 11 9 7 5 3 1 18 16 14 12 10 8 6 4 2 5pt (2) Given what you understand about how the acyl tail properties determine the physical properties of fatty acids, would you expect the melting temperature of elaidic acid to be higher , lower , or the same as oleic acid, i.e ., also 18:1( Δ 9 ) but with a cis bond? higher – the trans bond makes a straight chain that will pack better than the cis bond. (The T m of elaidic acid = 47deg C, of oleic acid = 14 degC) 5pt (3) How many stereoisomers of this sugar are theoretically possible? The number of possible stereoisomers for a compound with n chiral centers is 2 n ; in this case, 2 5 , or 32 possible stereoisomers. (4) The values of the specific rotation, [ α ] 20 D for the α and β anomers of D-galactose are 150.7˚ and 52.8˚, respectively. A mixture that is 60% α -D-galactose and 40% β -D- galactose is dissolved in water at 20˚C. 5pt (a) What is the initial specific rotation of the solution? [ α ] 20 D = 0.6(150.7) + 0.4(52.8) = 90.42 + 21.12 = 111.5˚ 5pt (b) After several hours, the specific rotation of this mixture reaches an equilibrium value of 80.2˚. What is its anomeric composition? if x = fraction of α , then (1- x ) = fraction of β 150.7 x + (1- x )52.8 = 80.2, solve for x ==> 0.28 28% α , 72% β
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2 (5) Using the Sanger dideoxy method of DNA sequencing gives the following gel: 5pt What is the sequence read from the gel? 5’-_
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This note was uploaded on 11/30/2009 for the course CH 55655 taught by Professor Marcotte during the Spring '09 term at University of Texas at Austin.

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ExamIV_Fall2007_key - Fall 2007 Dr. Marcotte EXAM IV CH339K...

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