Química Orgánica 2 · Acetales, iminas y equilibrios relacionados
Acetone azine from acetone and hydrazine
Condiciones: N2H4 (0.5 equiv), trace AcOH (assumed)
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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 14 pasos escritos
Hydrazine adds to the first acetone
A hydrazine nitrogen lone pair attacks the carbonyl carbon of acetone. Hydrazine is used here with a trace of acetic acid (assumed catalyst), as in most hydrazone preparations.
Las flechas curvas
- The nitrogen lone pair forms the C–N bond.
- The π pair moves onto oxygen.
Protonate the alkoxide
Acetic acid protonates the negative oxygen.
Las flechas curvas
- The alkoxide takes the proton.
- The pair stays on acetate.
Remove the N–H proton
Acetate removes the proton from the positive nitrogen, giving the carbinolamine.
Las flechas curvas
- Acetate takes the proton.
- The pair returns to nitrogen.
Protonate the OH
Acetic acid protonates the hydroxyl so it can leave as water.
Las flechas curvas
- The hydroxyl takes the proton.
- The pair stays on acetate.
Water leaves
The nitrogen lone pair forms C=N⁺ as water departs.
Las flechas curvas
- The nitrogen lone pair forms the C=N π bond.
- The C–O pair leaves with water.
Deprotonate to the hydrazone
Acetate removes the N–H proton, giving acetone hydrazone, which still has a free NH2.
Las flechas curvas
- Acetate takes the proton.
- The pair becomes the imine-type lone pair.
Check
Answer before you continue.
The NH2 adds to the second acetone
The terminal nitrogen of the hydrazone attacks the second acetone carbonyl.
Las flechas curvas
- The NH2 lone pair forms the second C–N bond.
- The π pair moves onto oxygen.
Protonate the alkoxide
Acetic acid protonates the second alkoxide.
Las flechas curvas
- The alkoxide takes the proton.
- The pair stays on acetate.
Remove the N–H proton
Acetate removes the proton from the positive nitrogen.
Las flechas curvas
- Acetate takes the proton.
- The pair returns to nitrogen.
Protonate the OH
Acetic acid protonates the second carbinolamine OH.
Las flechas curvas
- The hydroxyl takes the proton.
- The pair stays on acetate.
Second water leaves
The nitrogen lone pair forms the second C=N⁺ as water departs.
Las flechas curvas
- The nitrogen lone pair forms the C=N π bond.
- The C–O pair leaves with water.
Deprotonate to the azine
Acetate removes the last N–H proton, giving the azine and regenerating acetic acid.
Las flechas curvas
- Acetate takes the proton.
- The pair becomes the nitrogen lone pair.
Acetone azine
Both nitrogens of hydrazine are now doubly bonded to former carbonyl carbons; two waters are released.
Qué vas a practicar
Draw two successive condensations of hydrazine with two acetone molecules, each by addition, proton transfers and loss of water, to acetone azine.
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