HT2-03an - Some answers to Hour Examination #2, Chemistry...

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Some answers to Hour Examination #2, Chemistry 301-301A, 2003 1. (a) Bromide is not a strong nucleophile, and would never displace the poor leaving group ethoxide. S N 1 is impossible as a primary cation would have to be formed. (b) Here, protonation of the ether oxygen converts the leaving group from ethoxide, a miserable leaving group to ethanol, a good leaving group, and the reaction succeeds (p. 233). O Na + Br H 2 O no S N 2 reaction O H 2 O HBr OH Br + (a) (b) Br O H Br S N 2 (c) Ethoxide is not a good enough nucleophile to displace hydroxide. Moreover, there is a MUCH faster reaction possible, removal of a proton to give propoxide ion. Once again, the S N 1 reaction is impossible. O H OEt Na + OEt HOEt O O (c) no S N 2 reaction to give (d) Here, the first step,is tosylate formation (p. 233). The good leaving group tosylate is easily displaced by ethoxide to give the new ether. There will, of course, also be some E2 reaction to give propene.
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2. Just be careful to include the stereochemical demands of the E2 (180°, anti) and S N 2 reactions (inversion) in your arrow formalisms. Br
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This note was uploaded on 03/07/2010 for the course ORGO 1 AND V.0243 taught by Professor Jones during the Spring '10 term at NYU.

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HT2-03an - Some answers to Hour Examination #2, Chemistry...

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