Química Orgânica 2 · Acetais, iminas e equilíbrios relacionados
An aminoaldehyde closes its own ring
Condições: 4-Aminobutanal under mild acid and water-removing conditions; follow the intramolecular cyclic-imine branch rather than intermolecular oligomerization. No separate external amine is present. Counterions are not drawn; no stereochemistry is assigned without bond markers.
Desenhe este problema você mesmo
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
Water removes a proton from the iminium nitrogen. This gives the neutral C=N product and regenerates hydronium.
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.
Products
The ring contains the original aldehyde carbon, three methylene groups and nitrogen, with a C=N ring double bond. Both original N–H hydrogens have been transferred; the aldehyde oxygen leaves as water and nitrogen ends neutral.
O que você vai praticar
Form a five-membered cyclic imine while distinguishing ring atoms from the expelled oxygen.
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