Química Orgánica 2 · Síntesis y transformación de aminas
Ethylamine by the Curtius rearrangement
Condiciones: NaN3, acetone; then Δ (toluene); then H2O, Δ
Dibuja este problema tú mismo
Arrastra desde los electrones que se mueven hasta donde van, o toca uno y luego el otro. Cada flecha se revisa; Pista te ayuda cuando te atascas. No necesitas cuenta.
El mecanismo, paso a paso
Siguiente reproduce las flechas curvas de cada paso y las explica. Los pasos escritos están abajo.
Leer los 12 pasos escritos
Azide adds to the acyl chloride
An azide nitrogen attacks the very electrophilic carbonyl carbon of the acid chloride and the C=O π pair moves onto oxygen.
Las flechas curvas
- The azide lone pair forms the C–N bond.
- The C=O π pair moves onto oxygen.
Chloride leaves
The alkoxide re-forms C=O and expels chloride, the best leaving group, giving propanoyl azide.
Las flechas curvas
- The oxygen lone pair re-forms the C=O bond.
- The C–Cl pair leaves as chloride.
Acyl azide contributor
Shifting the azide π electrons puts the negative charge on the carbonyl-bound nitrogen and makes N2 a ready-made leaving group; this contributor shows the migration that follows.
Las flechas curvas
- The terminal lone pair forms the N≡N bond.
- The N=N π pair moves onto the carbonyl-bound nitrogen.
Ethyl migrates as N2 leaves
On heating, the ethyl group moves from carbon to nitrogen with its bonding pair while N2 departs, in one concerted step; the nitrogen lone pair forms the C=N bond of ethyl isocyanate. No free nitrene or cation forms, so a migrating stereocentre would keep its configuration.
Las flechas curvas
- The C–C pair carries the ethyl group to nitrogen.
- The nitrogen lone pair forms the C=N π bond.
- The N–N pair leaves with N2.
Carbon count
The rearrangement changes the skeleton.
Water adds to the isocyanate
Water attacks the central isocyanate carbon and the C=N π pair moves onto nitrogen.
Las flechas curvas
- A water lone pair forms the C–O bond.
- The C=N π pair moves onto nitrogen.
Water removes the oxonium proton
A second water deprotonates the positive oxygen.
Las flechas curvas
- Water takes the O–H proton.
- The O–H pair stays on oxygen.
Nitrogen takes a proton
The nitrogen anion takes a proton from hydronium, giving the carbamic acid.
Las flechas curvas
- The nitrogen lone pair takes the proton.
- The O–H pair stays on oxygen.
Deprotonate the carbamic acid
Water removes the acidic carbamic acid O–H proton, giving the carbamate ion.
Las flechas curvas
- Water takes the O–H proton.
- The O–H pair stays on oxygen.
Protonate nitrogen
Hydronium protonates the nitrogen, which makes it a neutral-amine leaving group.
Las flechas curvas
- The nitrogen lone pair takes the proton.
- The O–H pair stays on oxygen.
Lose CO2
The carboxylate oxygen forms a second C=O bond and the C–N bond breaks onto nitrogen, releasing CO2 and ethylamine.
Las flechas curvas
- The oxygen lone pair forms the C=O bond.
- The C–N pair stays on nitrogen.
Ethylamine
Ethylamine forms with CO2 and N2; the former carbonyl carbon left as CO2.
Qué vas a practicar
Draw formation of propanoyl azide, the concerted migration of ethyl to nitrogen with loss of N2, water addition to ethyl isocyanate, and decarboxylation to ethylamine.
Acabas de dibujar cada flecha de este problema.
Cada uno de los 5349 problemas de Orgánica 1 y 2 funciona así: comentarios en cada flecha, pistas cuando te atascas y un modo examen sin pistas. Gratis con una cuenta, sin tarjeta.
¿Atascado con tu propia tarea?
Tómale una foto: el primer escaneo es gratis, sin registrarte
¿Escaneas cada semana? Scan Standard: por unos problemas