Química Orgânica 2 · Ligações carbono–carbono com organometálicos
Carry nitrile addition through hydrolysis
Condições: Benzonitrile plus one equivalent of methyllithium, followed separately by aqueous HCl. Ph is unchanged phenyl; the nitrile has no alpha hydrogen. Two explicit HCl molecules and two waters enter at workup boundaries; hydrolyze completely. Dry ether first, then the stated separate workup. R⁻ is only an ionic organolithium electron-accounting model, not a solution-speciation claim.
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Add carbon to the nitrile
A ketimine anion, not an alkoxide, results from the dry addition.
As setas curvas
- The carbon nucleophile bonds to the nitrile carbon.
- One nitrile π pair moves onto nitrogen.
Begin acidic hydrolysis workup
Stage boundary: aqueous acid is now introduced; protonation first gives the neutral ketimine.
As setas curvas
- The anionic nitrogen accepts a workup proton.
- The acid pair goes to chloride.
Continue in acidic water
Stage boundary: an additional explicit acid molecule supplies the iminium-activation proton.
As setas curvas
- The imine nitrogen accepts a second proton.
- The acid bonding pair remains with chloride.
Continue the hydrolysis sequence
Stage boundary: one water is explicitly introduced as nucleophile. Carbon remains octet-compliant.
Nota: The incoming water supplies the ketone oxygen.
As setas curvas
- Water supplies the oxygen that will become the ketone oxygen.
- The iminium π pair moves to nitrogen.
Water takes back a proton
Another water molecule enters here. Water removes a proton from the product. The product becomes neutral and water becomes hydronium.
Nota: Solvent water removes a proton from the oxygen that just added. The resulting hydronium then protonates nitrogen.
As setas curvas
- The water oxygen takes a proton.
- The O–H bond electrons return to the positively charged oxygen, making it neutral.
Prepare the nitrogen leaving group
The explicit solvent proton shuttle turns NH₂ into NH₃⁺; no unassisted departure of amide anion is used.
As setas curvas
- Nitrogen accepts the proton carried by hydronium.
- The hydronium O–H pair returns to its oxygen.
Release the nitrogen fragment
The ketone is initially O-protonated and ammonia is retained in the snapshot.
As setas curvas
- The oxygen pair forms the carbonyl π bond.
- The C–N pair departs on neutral ammonia.
Complete the acidic product balance
Ammonium, rather than free ammonia, is retained as the nitrogen product in acidic workup.
As setas curvas
- Ammonia accepts the strongly acidic protonated-carbonyl proton.
- The O–H pair neutralizes the ketone oxygen.
Products
Acetophenone contains the original phenyl group and the added methyl; its oxygen came from water. Nitrile nitrogen becomes NH4+. The net reaction consumes one water and two HCl; the second water is a proton shuttle. Two chloride ions balance ammonium and the omitted lithium counterion.
O que você vai praticar
Track nitrile nitrogen all the way to ammonium and identify water as the ketone oxygen source.
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