Chapter 22. 2. Alpha Substitution. Replacement of a hydrogen on the carbon adjacent to the carbonyl, C=O.. =>. Chapter 22. 3. Condensation with Aldehyde or Ketone. Enolate ion attacks a C=O and the alkoxide is protonated. The net result is addition.. =>. Chapter 22. 4. Condensation with Esters. Loss of alkoxide ion results in nucleophilic acyl substitution..