Química Orgânica 2 · Hidrólise e esterificação
Trace an ester hydrolysis in acid
Condições: Methyl acetate in excess aqueous acid. Follow the forward hydrolysis branch with hydronium and water explicitly shown; the acid spectator anion is omitted throughout. Other oxygen-exchange pathways are not shown.
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Arraste dos elétrons que se movem até onde eles vão, ou toque em um e depois no outro. Cada seta é verificada; Dica ajuda quando você travar. Não precisa de conta.
O mecanismo, passo a passo
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Acidic reactant encounter
The explicit hydronium supplies the activation proton. Its conjugate water is retained as the proton shuttle throughout this pathway.
As setas curvas
- The base uses a lone pair to bond to the drawn hydrogen.
- The bond to hydrogen breaks, leaving its electrons on the atom that lost H.
Activated carbonyl
Water adds through oxygen, producing a three-coordinate incoming oxygen and a neutral former carbonyl hydroxyl.
As setas curvas
- The nucleophile uses a lone pair to form the new σ bond.
- The C=O π electrons move to oxygen so carbon keeps eight electrons.
First solvent-mediated proton exchange
Water removes a proton from the incoming oxygen. This separate transfer avoids an unsupported direct intramolecular proton jump.
As setas curvas
- The base uses a lone pair to bond to the drawn hydrogen.
- The bond to hydrogen breaks, leaving its electrons on the atom that lost H.
Prepare the leaving group
Solvent-mediated proton delivery converts the selected leaving group into a neutral species on bond cleavage.
As setas curvas
- The base uses a lone pair to bond to the drawn hydrogen.
- The bond to hydrogen breaks, leaving its electrons on the atom that lost H.
Tetrahedral intermediate in acid
The former carbonyl hydroxyl restores the pi bond while retaining its proton, so the acyl product is initially O-protonated. The leaving group is neutral after accepting the C–leaving-group pair.
As setas curvas
- An oxygen lone pair forms the C=O π bond again.
- The leaving group takes the electrons from the bond that breaks.
Resolve the activated product
Water removes the carbonyl-oxygen proton and restores hydronium. Every oxygen retains its identity through addition and elimination.
As setas curvas
- The base uses a lone pair to bond to the drawn hydrogen.
- The bond to hydrogen breaks, leaving its electrons on the atom that lost H.
Products
The incoming water oxygen becomes the carboxylic-acid hydroxyl and the original alkoxy oxygen remains in the departing alcohol. Hydronium is regenerated, so the net positive charge and all atoms are conserved.
O que você vai praticar
Complete all addition, proton-shuttle, elimination and catalyst-regeneration stages of acid-catalyzed hydrolysis.
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