Dolbier HW Solutions 592

Dolbier HW Solutions 592 - p-nitrophenoxide. Rate...

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( b ) The same principle applies here as in part ( a ). p -Nitrophenyl acetate reacts faster than m - nitrophenyl acetate (by about 45%) largely because p -nitrophenoxide is less basic and thus a better leaving group than m -nitrophenoxide. Resonance in p -nitrophenoxide is particularly effective because the p -nitro group is directly conjugated to the oxyanion; direct conjugation of these groups is absent in m -nitrophenoxide. ( c ) The reaction of ethyl bromide with a phenol is an S N 2 reaction in which the oxygen of the phe- nol is the nucleophile. The reaction is much faster with sodium phenoxide than with phenol, because an anion is more nucleophilic than a corresponding neutral molecule. Faster reaction: Slower reaction: ( d ) The answer here also depends on the nucleophilicity of the attacking species, which is a phe- noxide anion in both reactions. The more nucleophilic anion is phenoxide ion, because it is more basic than
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Unformatted text preview: p-nitrophenoxide. Rate measurements reveal that sodium phenoxide reacts 17 times faster with ethylene oxide (in ethanol at 70 ° C) than does its p-nitro derivative. ( e ) This reaction is electrophilic aromatic substitution. Because a hydroxy substituent is more activating than an acetate group, phenol undergoes bromination faster than does phenyl acetate. Resonance involving ester group reduces tendency of oxygen to donate electrons to ring. O CCH 3 O O CCH 3 O 2 1 More basic; better nucleophile 2 O Better delocalization of negative charge makes this less basic and less nucleophilic. O 2 N 2 O ArO 2 ArOCH 2 CH 2 O 2 CH 2 H 2 C O 1 1 ArOCH 2 CH 3 Br 2 Br CH 2 CH 3 H H ArO ArO 2 1 ArOCH 2 CH 3 Br 2 Br CH 2 CH 3 O 2 O 2 O 1 N 2 O 1 2 O N O 686 PHENOLS...
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This note was uploaded on 10/03/2011 for the course CHM 2210 taught by Professor Reynolds during the Fall '01 term at University of Florida.

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