Química Orgânica 2 · Síntese e transformação de aminas
Butan-1-ol from butan-1-amine and nitrous acid
Condições: NaNO2, HCl, H2O, 0 °C
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O mecanismo, passo a passo
Próximo mostra as setas curvas de cada passo e as explica. Os passos escritos estão abaixo.
Ler todos os 12 passos escritos
Protonate nitrous acid
NaNO2 and HCl give nitrous acid and hydronium. Hydronium protonates the nitrous acid OH so it can leave as water.
As setas curvas
- The OH oxygen takes the proton.
- The O–H pair stays on oxygen.
Water leaves: nitrosonium ion
The terminal oxygen lone pair forms a third N–O bond as water leaves, giving the nitrosonium ion, N≡O⁺.
As setas curvas
- The oxygen lone pair forms another N–O bond.
- The N–O pair leaves with water.
Amine attacks nitrosonium
The amine nitrogen attacks the nitrosonium nitrogen; one N≡O π pair moves onto oxygen.
As setas curvas
- The amine lone pair forms the N–N bond.
- One N≡O π pair moves onto oxygen.
Water removes an N–H proton
Water deprotonates the positive nitrogen, giving the N-nitrosamine.
As setas curvas
- Water takes the N–H proton.
- The N–H pair returns to nitrogen.
Protonate the nitroso oxygen
Hydronium protonates the nitroso oxygen, beginning a water-relayed tautomerization.
As setas curvas
- The nitroso oxygen takes the proton.
- The O–H pair stays on oxygen.
Form the diazohydroxide
Water removes the last N–H proton; that pair forms the N=N bond and the N=O π pair moves onto oxygen.
As setas curvas
- Water takes the N–H proton.
- The N–H pair forms the N=N π bond.
- The N=O π pair moves onto oxygen.
Protonate the OH
Hydronium protonates the diazohydroxide OH.
As setas curvas
- The OH oxygen takes the proton.
- The O–H pair stays on oxygen.
Water leaves: diazonium ion
The nitrogen lone pair forms the N≡N triple bond as water leaves, giving the butyldiazonium ion.
As setas curvas
- The nitrogen lone pair forms another N–N bond.
- The N–O pair leaves with water.
Water displaces N2
Alkyldiazonium ions are unstable even at 0 °C because N2 is a superb leaving group. Water attacks the primary carbon from the back side as N2 leaves.
As setas curvas
- A water lone pair forms the C–O bond.
- The C–N pair leaves with N2.
Alkyl vs aryl diazonium
Stability differs sharply.
Deprotonate the oxonium ion
Water removes the proton from the oxonium ion, giving butan-1-ol and regenerating hydronium.
As setas curvas
- Water takes the O–H proton.
- The O–H pair stays on oxygen.
Butan-1-ol
Butan-1-ol forms with N2. In practice the primary diazonium also gives butan-2-ol (via a hydride shift), butenes and chlorides, so this is a poor preparative route.
O que você vai praticar
Draw nitrosonium formation from nitrous acid, N-nitrosation of butan-1-amine, the proton transfers to the butyldiazonium ion, and displacement of N2 by water to give butan-1-ol.
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