CHEM267 Chapter Notes - Chapter Final: Nucleophilic Acyl Substitution, Haloform Reaction, Enol
18 Mar 2013
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22. 1 introduction to alpha carbon chemistry: enols and enolates. The c positions (indicated by greek letters) are relative to the position of the carbonyl group. In the presence of a catalytic acid or base, a ketone will exist in equilibrium with an enol: ketone is favoured at equilibrium, note: tautomers are not resonance structures! (different arrangement of atoms) Note: the enol tautomer is very reactive: the position is very nucleophilic due to resonance. When treated with a strong base, the position of a ketone is deprotonated to give a resonance- stabilized intermediate called an enolate. Enolates = ambident nucleophiles (they possess 2 nucleophilic sites) Note: c-attack is more common than o-attack! (even though o has the lone pairs) Note: enolates are more reactive than enols (b/c they possess a full negative charge) Note: only the protons of an aldehyde/ketone are acidic (lead to a resonance stabilized anion)
