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17 Reactions of Aromatic Compounds -- Part 4
The Organolithiums attack the carboxylate anions with dianions.
The dianion forms a hydrate of a ketone which quickly loses water.
We can add two equivalents to the carboxylic acid if the organolithium reagent is cheap.
The carbonyl group is attacked by the second equivalent.
The ketone is given by subsequent protonsation.
The synthesis of ketones can be started with nitriles.
The C " O bond of the carbonyl group is similar to the C " N triple bond.
The triple bond is attacked by the carbon atom.
The magnesium salt of an imine is given by attacking a nitrile with a Grignard or organolithium reagent.
The acidic hydrolysis of the imine leads to the ketone.
The reverse of acid-catalyzed imine formation is covered in Section 18-14.
The ketone is not being attacked.
The initial reaction forms an aluminum complex.
One might wonder if acids can be reduced back to aldehydes.
Reducing agents that are strong enough to reduce acids also reduce aldehydes faster.
The easiest way to reduce acids to aldehydes is to convert them to a functional group such as acid chloride.
The acidic hydroxy group is replaced by a chlorine atom in acid chlorides.
Treatment of carboxylic acids with thionyl chloride can be used to make acid chlorides.
LiAlH4 reduces acid chlorides all the way to primary alcohols.
The milder reducing agent butoxyaluminum hydride reacts faster with acid chlorides than with aldehydes.
It gives good yields of aldehydes.
Cold DIBAL-H doesn't reduce the aldehyde as much as LiAlH4.
The initial reaction forms an aluminum complex that is stable toward further reduction, but hydrolyzes to the aldehyde in the workup.
Grignard and organolithium reagents react with acid chlorides in a similar way to hydride reagents.
Grignard and organolithium reagents add acid chlorides to give ketones, but they add again to the ketones to give tertiary alcohols.
A weaker organometallic reagent is needed to stop at the ketone stage.
The reaction of two equivalents of the corresponding organolithium reagent with cuprous iodide formed the lithium dialkylcuprate.
R is for alkyl or aryl and G is for hydrogen.
Many reactions occur to give a wide variety of useful derivatives.
The reactivity of the carbonyl group is caused by the electronegativity of the oxygen atom.
It is open to attack from either face of the double bond because it is hybridized and flat.
The pi bond's electrons are forced out to the oxygen atom to form an alkoxide anion.
There are at least two examples of nucleophilic addition to alde hydes.
An alcohol is given by subsequent protonsation.
Attack by hydride causes an alkoxide to form an alcohol.
Under acidic conditions, water and alcohols can add activated carbonyl groups.
A weak carbonyl group can become acidic in a solution.
A weak nucleophile can attack a carbonyl group that is protonsated.
The acid-catalyzed addition of water across the carbonyl group of acetone is a reaction.
Section 18-12 talks about hydration of a ketone or aldehyde.
The base-catalyzed addition to a carbonyl group results from a strong nucleophilic attack.
The acid-catalyzed addition begins with the attack of a weak nucleophile.
The position of the equilibrium depends on the relative stabilities of the reactants and products.
They react more quickly than ketones, and the position of the equilibrium is more important than the products.
There is an electronic effect and a steric effect.
The aldehyde carbonyl group is slightly pages because there are only one electron-donating alkyl group.
There are combinations of these more exposed to nucleophilic attack in the carbonyl group chapter of an aldehyde.
NaBH(OAc)3 is a reducing agent that reduces aldehydes much more quickly than ketones.
Draw a complete Lewis structure.
There is a mechanism for the reduction of an aldehyde.
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