CHM 2123 Lecture Notes - Lecture 5: Proton Nuclear Magnetic Resonance, Acetophenone, Haloketone
17 Dec 2017
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Experiment 5 rxns of carbonyls under basic conditions. Hydrogens of ketones and aldehydes are acidic. Due to delocalization of the - charge upon deprotonation of the carbon via resonance. Stability depends on the alpha carbon acidity and resonance. Enolate is formed upon deprotonation of the hydrogen; competing rxns: Enolate is thermodynamically favoured (forms slower, can participate in further rxns) Nu addition is kinetically favoured product, but ti collapses and oh is kicked off (thus product is unstable and reverts back) Keto-enol tautomerism: the equilibrium between the keto form (ketone/aldehyde) and the enol form (alcohol) of a compound. These two forms are tautomers of each other. Aldehydes and ketones tend to dimerize in basic medium forming a new c-c bond. This forms an aldol (aldehyde and alcohol functional groups present in the product). The aldol product can then eliminate the hydroxyl group in protic solvents to form an unsaturated ketone or aldehyde (aldol condensation)
