8B_handout_feb18 - instead of substitution reactions R Cl O...

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Chem 8B, Handout for Feb 18, 2009, More Nucleophilic Acyl Substitution Reactions Sections 12.4-12.13 Fill in the following table comparing the reactivity (electrophilicity) of carbonyl compounds in nucleophilic acyl substitution reactions (based on the electronic effects and the stability of the leaving group. carbonyl how electrophilic? (ranking, where 1 = most electrophilic) electronic effects Leaving group (LG) conjugate acid of LG pKa of conjugate acid R Cl O R O O R OCH 3 O R OH O R N O CH 3 O R NH 2 O H CH 3 acid chloride anhydride ester carboxylic acid secondary amide primary amide ranking = 1 most electrophilic (no catalyst needed) inductive electron- withdrawing effects; No resonance ranking = 5 least electrophilic (need catalyst + heat) ranking = 4 not very electrophilic (need H + catalyst) ranking = 3 not very electrophilic (need H + catalyst) ranking = 2 good electrophilic (no catalyst needed) electron-donating effects from N; resonance stabilization R N O H CH 3 (Recall that the aldehyde and ketone do not have a leaving group, so they undergo addition reactions
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Unformatted text preview: instead of substitution reactions.) R Cl O + HO CH 3 R OCH 3 O substitution product electrophile nucleophile Nucleophilic Acyl Substitution reaction Nucleophiles = water, alcohols, amines, hydride (H: — ), and carbon anions (such as RLi and RMgBr) Acylation reactions for the synthesis of Aspirin TM Synthetic Option 1: (be able to draw a curved arrow mechanism for this reaction) OH OH O O OH O O H 3 C salicylic acid acetylsalicylic acid aspirin TM acetylation reaction + + Synthetic Option 2: OH OH O O OH O O H 3 C salicylic acid acetylsalicylic acid aspirin TM + + What are the advantages of synthetic option 1? What are the advantages of synthetic option 2? What structural features do aspirin and heroin have in common? O O H O N H (heroin) H 3 C O H 3 C O diacetylmorphine CH 3 O OH O O H 3 C acetylsalicylic acid aspirin TM...
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