Química Orgânica 2 · Hidrólise e esterificação
Acid hydrolysis of urea to ammonium and CO2
Condições: H3O⁺, H2O, Δ
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 11 passos escritos
Protonate the urea oxygen
Hydronium protonates the carbonyl oxygen of urea. Two nitrogen lone pairs stabilise the cation, which is why urea is so unreactive and needs heat.
As setas curvas
- The carbonyl oxygen lone pair takes the proton.
- The O–H bond pair stays on the water oxygen.
Water adds
Water attacks the activated carbon, giving a tetrahedral oxonium ion.
As setas curvas
- A water lone pair forms the new C–O bond.
- The C=O π electrons move onto the protonated oxygen.
Water removes the extra proton
A water molecule takes the proton from the oxonium oxygen.
As setas curvas
- A lone pair on the base takes the proton.
- The O–H bond pair stays on the atom that loses the proton.
Protonate a nitrogen
Hydronium protonates one nitrogen; in the tetrahedral intermediate it is an ordinary basic amine nitrogen.
As setas curvas
- The nitrogen lone pair takes the proton.
- The O–H bond pair stays on the atom that loses the proton.
Ammonia leaves
An OH lone pair re-forms the C=O and neutral ammonia departs, giving protonated carbamic acid.
As setas curvas
- An oxygen lone pair forms the C=O π bond.
- The C–N bond breaks onto nitrogen.
Ammonia is protonated
Ammonia takes the proton from the protonated carbamic acid, giving ammonium.
As setas curvas
- The ammonia lone pair takes the proton.
- The O–H bond pair stays on the atom that loses the proton.
What happens to carbamic acid?
Carbamic acid is not a stable compound.
Protonate the carbamic acid nitrogen
Fresh hydronium protonates the nitrogen of carbamic acid, turning it into a neutral ammonia leaving group.
As setas curvas
- The nitrogen lone pair takes the proton.
- The O–H bond pair stays on the atom that loses the proton.
Decarboxylation
Water removes the O–H proton; those electrons form a second C=O as the C–N bond breaks, releasing CO2 and ammonia.
As setas curvas
- A water lone pair takes the O–H proton.
- The O–H bond pair forms the new C=O π bond.
- The C–N bond breaks onto nitrogen.
The second ammonia is protonated
Ammonia takes a proton from hydronium; in acid both nitrogens end as ammonium.
As setas curvas
- The ammonia lone pair takes the proton.
- The O–H bond pair stays on the atom that loses the proton.
Ammonium and CO2
Two ammonium ions and carbon dioxide form from one urea and one water (two hydronium ions consumed).
O que você vai praticar
Draw acid hydrolysis of urea: O-protonation, water addition, proton relay to nitrogen, loss of ammonia, then N-protonation and decarboxylation of carbamic acid.
Você acabou de desenhar cada seta deste problema.
Cada um dos 5349 problemas de Orgânica 1 e 2 funciona assim: feedback em cada seta, dicas quando você travar e um modo prova sem dicas. Grátis com uma conta, sem cartão.
Travou na sua própria lição?
Tire uma foto: o primeiro scan é grátis, sem cadastro
Você escaneia toda semana? Scan Standard: por cerca de problemas