Química Orgânica 2 · Acetais, iminas e equilíbrios relacionados
Hydrolyzing an enamine carbon skeleton
Condições: The acetone-derived dimethyl enamine in excess acidic water; trace carbon protonation and complete hydrolysis to acetone plus dimethylammonium. The productive carbon-protonation branch is specified. Counterions are not drawn; no stereochemistry is assigned without bond markers.
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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
Próximo mostra as setas curvas de cada passo e as explica. Os passos escritos estão abaixo.
Ler todos os 8 passos escritos
Move the electrons
Carbon protonation generates the hydrolysis-competent iminium contributor while retaining a full carbon octet.
As setas curvas
- The enamine pi bond captures a proton at the carbon remote from nitrogen.
- The acid O–H pair returns to the water oxygen.
- Nitrogen supplies the iminium pi bond.
Move the electrons
Water adds to iminium carbon and the C=N pair restores the nitrogen lone pair.
As setas curvas
- The nucleophile uses a lone pair to form the new single bond.
- The π electrons move off carbon, keeping eight electrons around it.
Move the electrons
The water-derived oxonium becomes a neutral carbinolamine hydroxyl group.
As setas curvas
- The base uses a lone pair to accept a proton from the O–H bond.
- The bond to hydrogen breaks, and its electrons stay on the atom losing the proton.
Move the electrons
Protonation makes nitrogen a neutral-amine leaving group after C–N cleavage.
As setas curvas
- The base uses a lone pair to accept a proton from the O–H bond.
- The bond to hydrogen breaks, and its electrons stay on the atom losing the proton.
Move the electrons
The oxygen lone pair supplies C=O while the C–N pair goes to the leaving nitrogen.
As setas curvas
- A lone pair forms the new π bond.
- The leaving group takes the electrons from the single bond.
Move the electrons
Solvent removes the proton from the new carbonyl oxygen.
As setas curvas
- The base uses a lone pair to accept a proton from the O–H bond.
- The bond to hydrogen breaks, and its electrons stay on the atom losing the proton.
Move the electrons
Under the stated acidic endpoint, the released amine is trapped as its ammonium ion rather than left as an unrealistically unprotonated bulk product.
As setas curvas
- The base uses a lone pair to accept a proton from the O–H bond.
- The bond to hydrogen breaks, and its electrons stay on the atom losing the proton.
Products
The enamine C=C bond becomes a methyl C–H bond and a carbonyl at the carbon originally bonded to nitrogen. The incoming water oxygen is retained in acetone; dimethylamine leaves and is protonated to its four-bond ammonium form.
O que você vai praticar
Relate carbon protonation to iminium hydrolysis and the secondary-ammonium endpoint.
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