Química Orgânica 2 · Acetais, iminas e equilíbrios relacionados
A secondary amine changes the condensation endpoint
Condições: Acetone plus dimethylamine, mild acid and water removal; follow the enamine branch. 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 7 passos escritos
Move the electrons
Hydronium protonates the carbonyl oxygen, making the carbonyl carbon easier to attack.
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
Nitrogen uses its lone pair to attack the carbonyl carbon. Nitrogen now has four bonds and a positive charge.
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
Water removes a proton from the positively charged nitrogen. This gives a neutral carbinolamine: a carbon bonded to both OH and nitrogen.
As setas curvas
- The base uses a lone pair to accept a proton from the N–H bond.
- The bond to hydrogen breaks, and its electrons stay on the atom losing the proton.
Move the electrons
Add a proton to the OH group so it can leave as water.
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 nitrogen lone pair forms the C=N bond as water leaves. Nitrogen carries a positive charge in this iminium ion.
As setas curvas
- A lone pair forms the new π bond.
- The leaving group takes the electrons from the single bond.
Move the electrons
The secondary-amine-derived iminium has no N–H bond. Carbon deprotonation, not nitrogen deprotonation, produces the neutral enamine.
As setas curvas
- Solvent accepts the specified alpha hydrogen.
- The alpha C–H pair supplies the carbon–carbon pi bond.
- The iminium pi pair returns to nitrogen.
Products
The product has a C=C bond adjacent to a neutral nitrogen with three sigma bonds and one lone pair. Water contains the carbonyl oxygen; removal of an alpha proton regenerates hydronium.
O que você vai praticar
Choose alpha-carbon deprotonation when the iminium nitrogen has no removable proton.
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