FinalAns2.cwk - Answers to the Final examination, Chemistry...

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Answers to the Final examination, Chemistry 302X - 2006 1. (a) CHO OH H H HO OH H OH H CH 2 OH CHO OH H H HO H HO OH H CH 2 OH CH 3 OH 2 CH 3 OH O OH HO HOCH 2 OCH 3 HO D-Glucose D-Galactose or + unknown - either α or β unknown - this is C4 of either glucose or galactose (b) B O OAc AcO AcOCH 2 OCH 3 AcO unknown - either α or β unknown - this is C4 of either glucose or galactose
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(c) A Ac 2 O B O OAc AcO AcOCH 2 OCH 3 AcO H-1 H H H H-4 Py must be equatorial because of the small Ax-Eq coupling --therefore the OMe is axial, alpha must be axial because of the two large Ax-Ax couplings. Therefore the OAc on this carbon is equatorial, and the original sugar must have been glucose 2. a) Convert butadiene into 1,4-dibromobutane: 1. BH 3 2. HOOH/HO 3. HBr convert acetic acid into ethyl acetate EtOH/acid cat. make acetacetic ester through a Claisen condensation of ethyl acetate: 1. full eq. of EtONa 2. pH = 7 (note - you could do the first alkylation with the anion formed before raising the pH to 7) now alkylate acetoacetic ester twice with 1,4-dibromobutane 1. EtO 2. 1,4-dibromobutane (run it twice) Now you have: EtOOC O CH 3 Finally hydrolyze the ester and decarboxylate: 1. H 2 O/H 3 O + 2. heat.
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(b) First add HBr to cyclopentene to give cyclopentyl bromide. Next make cyclopentyllithium by treating the bromide with Li. Finally, treat acetic acid with two eq. of cyclopentyllithium, followed by hydrolysis. (c) Oxidize the starting alcohol to cyclopentanecarboxaldehyde with CrO 3 /pyridine. Then make the tosylate out of the alcohol with tosyl chloride. Eliminate with (CH
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FinalAns2.cwk - Answers to the Final examination, Chemistry...

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