CHEM 239 sample_exam_ex3_key

CHEM 239 sample_exam_ex3_key - Chemistry 239 Autumn, 2004...

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Unformatted text preview: Chemistry 239 Autumn, 2004 Sample Exam 3 Answer Key Your name: Student #1 Sign here to indicate your approval of public return of your paper: 1 (24 pts.) Give structures or names for the compounds below. c02H H OH HO H H OH H OH C02H oleic acid (show stereochemistry) a lecithin quinone D-fructose D-glucaric acid D-mannose Fischer projection Fischer projection Fischer projection fH2°C°R H3(CH2)1 oc02H R'COz—CID—H 0 II + CHz-O-Pl-O-CH 2CH2NH3 O CH3(CH2)7 (CH2)7C02H 2 (5 pts.) Complete a balanced equation for a proton transfer between the reactants below, label the stronger and weaker acids involved, and indicate whether the position of equilibrium is favorable (to the right) or unfavorable (to the left). PhNH3+ + PhO' <———> PhNH2 + PhOH stronger acid T> weaker acid [pKa 5] favorable [pKa 10] Chem 239 2004 Autumn, Sample Exam 3 2 Answer Key p. 3 (24 pts.) In the reactions below fill in the missing items (starting material[s], reagents and conditions over the arrow, or main organic product[s]). PhOCH3 + HBr —'——-> PhOH + CH3BI' ‘ pyridine Aco o i 4 (7 pts.) Draw the structure of the aldaric acid that would be formed from D—idose below. Indicate whether the aldaric acid would be optically active or not. Can you draw the structure of a different aldose that would give the same aldaric acid as that from D-idose (explain)? CHO C02H can't draw another aldose HO H Ho H that would give the same HI; 3" H 0” aldaric acid because the H OH HI? 3H structure to the right is also D-idose and not a CH20H C02H different aldose opficaHy acfive Chem 239 Autumn, 2004 Sample Exam 3 Answer Key p. 3 W 5 (8 pts.) A branched polysaccharide is hydrolyzed by B—glycosidase enzymes but not by 06 -glycosidase enzymes. Hydrolysis gives mainly 2,4,6-tri-O—methyl—D~allose, along with a small amount of 2,6—di-O—methyl-D-allose. Sketch the structure (showing all rings as chairs) of the branching point of the polysaccharide, as well as the repeating chain structures leading away from the branch point. 6 (6 pts.) Classify the terpene vetivazulene (below) according to type of terpene (e.g., monoterpene, etc.) and outline how isoprene skeletons might form the structure. sesquiterpene [C15] Chem 239 Autumn, 2004 Sample Exam 3 Answer Key p. 4 7 (8 pts.) Show curved arrows for all steps in the mechanism to form the sesquiterpene below from a geometric isomer of farnesyl pyrophosphate. 8 (10 pts.) The naturally occuring terpene hydrocarbon y—terpinene reacts with 2 mol equivalents of hydrogen upon catalytic hydrogenation to give 1-methyl-4- isopropylcyclohexane. Ozonolysis of y—terpinene gives the products shown below (1_ mol equiv. each). Propose a structure for y—terpinene and show shorthand equations for both reactions. 9 fi’ HCCHZCCH(CH3)2 f? f? + Chem 239 Autumn, 2004 Sample Exam 2 Answer Key p. 5 9 (8 pts.) Assume the conversion below takes place in three steps. Show curved arrows for the mechanism and draw the structures of the two intermediates required. (Use only one or two curved arrows per step.) ...
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CHEM 239 sample_exam_ex3_key - Chemistry 239 Autumn, 2004...

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