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Unformatted text preview: Moderating Reactivity through Synthetic Modification Acetylation of Phenols and Anilines Both phenols (Ar- OH ) and anilines (Ar- NH 2 ) are extremely reactive in most electrophilic aromatic substitution reactions. Sometimes it is necessary to reduce this reactivity by synthetic modification of the substituent groups. :OH : phenol (more reactive) :NH 2 aniline (more reactive) CH 3 COCCH 3 O = O = acetic anhydride acetylation CH 3 COONa + CH 3 COCCH 3 O = O = acetic anhydride + acetylation :OCCH 3 : O = phenyl acetate (less reactive) :NHCCH 3 O = acetanilide (less reactive) An Explanation of the Decreased Reactivity The decrease in reactivity of phenol and aniline upon acetylation is explained through resonance theory . Additional resonance structures may be written that show movement of the nonbonding electrons towards the carbonyl function and away from the benzene ring. Accordingly, the nonbonding electron pairs will be less able to donate electron density into the aromatic ring....
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This note was uploaded on 10/20/2009 for the course CHEM 322BL at USC.
- Organic chemistry