Carbon Nucleophiles
This is an extremely important reaction because it allows the formation of new C–C single or C=C double bonds and increases the complexity of the product.
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Cyanide
Cyanide, perhaps the simplest carbon nucleophile, reacts with aldehydes and ketones to give cyanohydrins.
The reaction is very simple and useful because the CN group can be converted into many other functional groups.
Lithium and magnesium organometallics (Grignard)
Depending on whether formaldehyde, an aldehyde or a ketone is used, a primary, secondary or tertiary alcohol is obtained, respectively.
Many functions compete with the carbonyl group or simply destroy the organometallic, such as alcohols, amines and carboxylic acids, among many others.
Acetylides
Click here to recall the acidity of terminal alkynes.
Alkynides or acetylides, obtained by the action of a strong base on a terminal alkyne, are excellent nucleophiles that add easily to carbonyl groups.
Many functions compete with the carbonyl group or simply destroy the alkynide, such as alcohols, amines and carboxylic acids, among many others.
Phosphorus ylides
This reaction was already mentioned in the chapter on alkenes, because it is used to prepare them.
The key compound in this process is the phosphorus ylide, which forms because the hydrogens next to the phosphorus of a phosphonium salt are somewhat acidic. This distinguishes phosphonium salts from ammonium salts. What causes this acidity of phosphonium salts?
The only way to explain such a high acidity is that phosphorus can use its 3d orbitals to delocalize the negative charge of the ylide. Nitrogen cannot!