Editing Nucleophilic addition (section)

===Addition to carbonyl groups===
With a carbonyl compound as an electrophile, the nucleophile can be:<ref name=March />
* [[water]] in [[Hydration reaction|hydration]] to a [[geminal]] [[diol]] (hydrate)
* an [[Alcohol (chemistry)|alcohol]] in [[acetalisation]] to an [[acetal]]
* a [[hydride]] in [[reducing agent|reduction]] to an [[Alcohol (chemistry)|alcohol]]
* an [[amine]] with formaldehyde and a carbonyl compound in the [[Mannich reaction]]
* an [[enolate ion]] in an [[aldol reaction]] or [[Baylis–Hillman reaction]]
* an [[organometallic]] [[nucleophile]] in the [[Grignard reaction]] or the related [[Barbier reaction]] or a [[Reformatskii reaction]]
* [[ylide]]s such as a [[Wittig reagent]] or the [[Corey–Chaykovsky reagent]]  or α-silyl carbanions in the [[Peterson olefination]]
* a phosphonate carbanion in the [[Horner–Wadsworth–Emmons reaction]]
* a pyridine zwitterion in the [[Hammick reaction]]
* an [[acetylide]] in [[alkynylation]] reactions.
* a [[cyanide ion]] in [[cyanohydrin reaction]]s

In many nucleophilic reactions, addition to the carbonyl group is very important. In some cases, the C=O [[double bond]] is [[Organic redox reaction|reduced]] to a C-O [[single bond]] when the nucleophile bonds with carbon. For example, in the cyanohydrin reaction a cyanide ion forms a [[Carbon–carbon bond|C-C bond]] by breaking the carbonyl's double bond to form a [[cyanohydrin]].