Mecanismo de condensação aldólica

Mecanismo de condensação aldólica, passo a passo

Cada etapa começa com o seu desenho, setas curvas incluídas; o texto abaixo dele descreve esse desenho.

1. Remove an alpha proton

   

   Hydroxide removes the alpha proton next to the carbonyl, forming an enolate. Hydroxide becomes water.

   As setas curvas do desenho:

   • The base removes an alpha hydrogen next to the carbonyl.
   • The alpha C–H electrons form a π bond to the carbonyl carbon.
   • The carbonyl π electrons move onto oxygen.

2. Draw the other resonance form

   

   These are two resonance forms of the same enolate, not separate molecules. No proton moves between them.

   As setas curvas do desenho:

   • An oxygen lone pair forms the carbonyl π bond.
   • The π electrons move onto the alpha carbon as a lone pair.

3. Lose hydroxide

   

   The enolate loses hydroxide as the C=C bond forms. This gives a neutral enone, with a C=C bond next to C=O.

   As setas curvas do desenho:

   • The alpha-carbon lone pair forms a C=C π bond next to the carbonyl.
   • The C–O bond electrons leave with oxygen, releasing hydroxide.

4. Products

   

   The carbonyl stays in place, and the bond between the alpha and beta carbons becomes double. The base oxygen is now in water. The original alcohol oxygen leaves as hydroxide, regenerating the base.