Editing Nucleophile (section)

== Types ==
Examples of nucleophiles are anions such as Cl<sup>−</sup>, or a compound with a [[lone pair]] of electrons such as NH<sub>3</sub> ([[ammonia]]) and PR<sub>3</sub>.{{cn|date=March 2024}}

In the example below, the [[oxygen]] of the hydroxide ion donates an electron pair to form a new chemical bond with the [[carbon]] at the end of the [[alkyl halide|bromopropane]] molecule. The bond between the carbon and the [[bromine]] then undergoes [[heterolytic fission]], with the bromine atom taking the donated electron and becoming the [[bromide]] ion (Br<sup>−</sup>), because a S<sub>N</sub>2 reaction occurs by backside attack. This means that the hydroxide ion attacks the carbon atom from the other side, exactly opposite the bromine ion. Because of this backside attack, S<sub>N</sub>2 reactions result in an inversion of the [[Molecular configuration|configuration]] of the electrophile. If the electrophile is [[chiral]], it typically maintains its chirality, though the S<sub>N</sub>2 product's [[absolute configuration]] is flipped as compared to that of the original electrophile.{{cn|date=March 2024}}
:[[File:hydrox subst.png|Displacement of bromine by a hydroxide]]

===Ambident nucleophile===
An '''ambident nucleophile''' is one that can attack from two or more places, resulting in two or more products. For example, the [[thiocyanate]] ion (SCN<sup>−</sup>) may attack from either the sulfur or the nitrogen. For this reason, the [[SN2 reaction|S<sub>N</sub>2 reaction]] of an alkyl halide with SCN<sup>−</sup> often leads to a mixture of an alkyl thiocyanate (R-SCN) and an alkyl [[isothiocyanate]] (R-NCS). Similar considerations apply in the [[Kolbe nitrile synthesis]].{{cn|date=March 2024}}

=== Halogens ===
While the [[halogens]] are not nucleophilic in their diatomic form (e.g. I<sub>2</sub> is not a nucleophile), their anions are good nucleophiles. In polar, protic solvents, F<sup>−</sup> is the weakest nucleophile, and I<sup>−</sup> the strongest; this order is reversed in polar, aprotic solvents.<ref>''Chem 2401 Supplementary Notes''. Thompson, Alison and Pincock, James, Dalhousie University Chemistry Department</ref>

=== Carbon ===
{{See also|Carbanion}}
Carbon nucleophiles are often [[Organometallic chemistry|organometallic reagent]]s such as those found in the [[Grignard reaction]], [[Blaise reaction]], [[Reformatsky reaction]], and [[Barbier reaction]] or reactions involving [[organolithium reagent]]s and [[acetylide]]s. These reagents are often used to perform [[nucleophilic addition]]s.{{cn|date=March 2024}}

[[Enol]]s are also carbon nucleophiles. The formation of an enol is catalyzed by [[Acid catalysis|acid]] or [[Base (chemistry)|base]]. Enols are [[wikt:ambident|ambident]] nucleophiles, but, in general, nucleophilic at the [[Alpha and beta carbon|alpha carbon]] atom. Enols are commonly used in [[condensation reaction]]s, including the [[Claisen condensation]] and the [[aldol condensation]] reactions.{{cn|date=March 2024}}

=== Oxygen ===
Examples of oxygen nucleophiles are [[water]] (H<sub>2</sub>O), [[hydroxide]] anion, [[Alcohol (chemistry)|alcohol]]s, [[alkoxide]] anions, [[hydrogen peroxide]], and [[Carboxylate|carboxylate anions]].
Nucleophilic attack does not take place during intermolecular hydrogen bonding.

=== Sulfur ===
Of sulfur nucleophiles, [[hydrogen sulfide]] and its salts, [[thiol]]s (RSH), thiolate anions (RS<sup>−</sup>), anions of thiolcarboxylic acids (RC(O)-S<sup>−</sup>), and anions of dithiocarbonates (RO-C(S)-S<sup>−</sup>) and dithiocarbamates (R<sub>2</sub>N-C(S)-S<sup>−</sup>) are used most often.

In general, ''sulfur is very nucleophilic because of its large size'', which makes it readily polarizable, and its lone pairs of electrons are readily accessible.

=== Nitrogen ===
Nitrogen nucleophiles include [[ammonia]], [[azide]], [[amine]]s, [[nitrite]]s, [[hydroxylamine]], [[hydrazine]], [[carbazide]], [[phenylhydrazine]], [[semicarbazide]], and [[amide]].

=== Metal centers ===
Although metal centers (e.g., Li<sup>+</sup>, Zn<sup>2+</sup>, Sc<sup>3+</sup>, etc.) are most commonly cationic and electrophilic (Lewis acidic) in nature, certain metal centers (particularly ones in a low oxidation state and/or carrying a negative charge) are among the strongest recorded nucleophiles and are sometimes referred to as "supernucleophiles." For instance, using methyl iodide as the reference electrophile, Ph<sub>3</sub>Sn<sup>–</sup> is about 10000 times more nucleophilic than I<sup>–</sup>, while the Co(I) form of [[Vitamin B12|vitamin B<sub>12</sub>]] (vitamin B<sub>12s</sub>) is about 10<sup>7</sup> times more nucleophilic.<ref>{{Cite journal|last1=Schrauzer|first1=G. N.|last2=Deutsch|first2=E.|last3=Windgassen|first3=R. J.|date=April 1968|title=The nucleophilicity of vitamin B(sub 12s)|journal=Journal of the American Chemical Society|language=en|volume=90|issue=9|pages=2441–2442|doi=10.1021/ja01011a054|pmid=5642073|issn=0002-7863}}</ref> Other supernucleophilic metal centers include low oxidation state carbonyl metalate anions (e.g., CpFe(CO)<sub>2</sub><sup>–</sup>).<ref>{{Cite journal|last1=Dessy|first1=Raymond E.|last2=Pohl|first2=Rudolph L.|last3=King|first3=R. Bruce|date=November 1966|title=Organometallic Electrochemistry. VII. 1 The Nucleophilicities of Metallic and Metalloidal Anions Derived from Metals of Groups IV, V, VI, VII, and VIII|journal=Journal of the American Chemical Society|language=en|volume=88|issue=22|pages=5121–5124|doi=10.1021/ja00974a015|issn=0002-7863}}</ref>