Editing Nucleophilic addition

{{Short description|Chemical reaction involving the addition of a nucleophile to an electrophile}}
In [[organic chemistry]], a '''nucleophilic addition''' ('''A<sub>N</sub>''') reaction is an [[addition reaction]] where a [[chemical compound]] with an [[electrophile|electrophilic]] [[double bond|double]] or [[triple bond]] reacts with a [[nucleophile]], such that the double or triple bond is broken. Nucleophilic additions differ from [[electrophilic addition]]s in that the former reactions involve the group to which atoms are added accepting electron pairs, whereas the latter reactions involve the group donating electron pairs. 

== Addition to carbon–heteroatom double bonds ==
Nucleophilic addition reactions of nucleophiles with electrophilic double or triple bond (π bonds) create a new carbon center with two additional single, or σ, bonds.<ref name=March>March Jerry; (1985). Advanced Organic Chemistry reactions, mechanisms and structure (3rd ed.). New York: John Wiley & Sons, inc. {{ISBN|0-471-85472-7}}</ref> Addition of a nucleophile to carbon–heteroatom double or triple bonds such as >C=O or -C≡N show great variety. These types of bonds are [[polar bond|polar]] (have a large difference in [[electronegativity]] between the two atoms); consequently, their carbon atoms carries a partial positive charge. This makes the molecule an electrophile, and the carbon atom the electrophilic center; this atom is the primary target for the nucleophile. Chemists have developed a geometric system to describe the approach of the nucleophile to the electrophilic center, using two angles, the [[Bürgi–Dunitz angle|Bürgi–Dunitz]] and the [[Flippin–Lodge angle|Flippin–Lodge]] angles after scientists that first studied and described them.<ref name="flemingbook">{{cite book |author=Fleming, Ian |title=Molecular orbitals and organic chemical reactions |publisher=Wiley |location=New York |year=2010 |isbn=978-0-470-74658-5 }}</ref><ref name="urgi">{{Cite journal | last1 = Bürgi | first1 = H. B. | last2 = Dunitz | first2 = J. D. | author-link2 = Jack D. Dunitz| last3 = Lehn | first3 = J. M. | last4 = Wipff | first4 = G. | title = Stereochemistry of reaction paths at carbonyl centres | doi = 10.1016/S0040-4020(01)90678-7 | journal = Tetrahedron | volume = 30 | issue = 12 | pages = 1563 | year = 1974 }}</ref><ref>{{cite journal |author1=H. B. Bürgi |author2=J. D. Dunitz |author3=J. M. Lehn |author4=G. Wipff | title= Stereochemistry of reaction paths at carbonyl centres | journal= [[Tetrahedron (journal)|Tetrahedron]] | year=1974 | volume=30 | issue=12 | pages=1563–1572 | doi = 10.1016/S0040-4020(01)90678-7 }}</ref>
:[[Image:NucleophilicAdditionsToCarbonyls.svg|300px|Nucleophilic addition to a carbonyl]]
This type of reaction is also called a '''1,2-nucleophilic addition'''. The [[stereochemistry]] of this type of nucleophilic attack is not an issue, when both alkyl substituents are dissimilar and there are not any other controlling issues such as [[chelation]] with a [[Lewis acid]], the reaction product is a [[racemate]]. Addition reactions of this type are numerous. When the addition reaction is accompanied by an elimination the reaction is a type of substitution or an [[addition-elimination reaction]].

===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]].

===Addition to nitriles===
With [[nitrile]] electrophiles, nucleophilic addition take place by:<ref name=March />
* hydrolysis of a [[nitrile]] to form an [[amide]] or a [[carboxylic acid]]
* organozinc nucleophiles in the [[Blaise reaction]]
* [[Alcohol (chemistry)|alcohol]]s in the [[Pinner reaction]].
* the (same) nitrile α-carbon in the [[Thorpe reaction]]. The intramolecular version is called the [[Thorpe–Ziegler reaction]].
* [[Grignard reagent]]s to form [[imine]]s.<ref>{{cite journal|last1=Moureu|first1=Charles|last2=Mignonac|first2=Georges|title=Les Cetimines|journal=[[Annales de chimie et de physique]]|date=1920|volume=9|issue=13|pages=322–359|url=http://babel.hathitrust.org/cgi/pt?id=uc1.b3816273;view=1up;seq=682|access-date=18 June 2014}}</ref> The route affords [[ketone]]s following [[hydrolysis]]<ref>{{cite journal|last1=Moffett|first1=R. B.|last2=Shriner|first2=R. L.|title=ω-Methoxyacetophenone|journal=Organic Syntheses|date=1941|volume=21|page=79|doi=10.15227/orgsyn.021.0079}}</ref> or [[Primary (chemistry)|primary]] [[amine]]s following [[Hydrogenation of carbon–nitrogen double bonds|imine reduction]].<ref>{{cite journal|last1=Weiberth|first1=Franz J.|last2=Hall|first2=Stan S.|title=Tandem alkylation-reduction of nitriles. Synthesis of branched primary amines|journal=Journal of Organic Chemistry|date=1986|volume=51|issue=26|pages=5338–5341|doi=10.1021/jo00376a053}}</ref>

== Addition to carbon–carbon double bonds ==
When a [[nucleophile]] X<sup>−</sup> adds to an [[alkenes|alkene]], the driving force is the transfer of negative charge from X to the electron-poor [[Saturated and unsaturated compounds|unsaturated]] -C=C- system.  This occurs through the formation of a [[covalent bond]] between X and one carbon atom, concomitant with the transfer of electron density from the [[pi bond]] onto the other carbon atom (step 1).<ref name=March />  During a [[One-pot synthesis|telescoped second reaction]] or [[Workup (chemistry)|workup]] (step 2), the resulting negatively charged [[carbanion]] combines with an [[Electrophile|electrophilic]] Y to form the second covalent bond.{{cn|date=March 2024}}

:[[Image:NucleophilicAdditionGeneral.svg|300px|Nucleophilic addition to an alkene]]

Unsubstituted and unstrained alkenes are typically insufficiently polar to admit nucleophilic addition, but a few exceptions are known. 

The strain energy in [[fullerene]]s weakens their [[double bond|double-bonds]]; addition thereto is the [[Bingel reaction]].

Bonds adjacent to an [[Electron-withdrawing group|electron-withdrawing]] substituent (e.g. a [[carbonyl group]], [[nitrile]], or [[fluoride]]) readily admit nucleophilic addition.  In this process, [[conjugate addition reaction|conjugate addition]], the nucleophile X adds [[Locant|β]] to the substituent, because then said substituent [[Inductive effect|inductively]] stabilizes the product's negative charge.  [[Aromaticity|Aromatic]] substituents, although typically [[Electrophile|electrophilic]], can also sometimes stabilize negative charge; for example, [[styrene]] reacts in [[toluene]] with [[sodium]] to give 1,3-diphenylpropane:<ref>''Sodium-catalyzed Side Chain Aralkylation of Alkylbenzenes with Styrene'' Herman Pines, Dieter Wunderlich J. Am. Chem. Soc.; 1958; 80(22)6001–6004. {{doi|10.1021/ja01555a029}}</ref>

== References ==
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{{commons category|Nucleophilic addition reactions}}
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[[Category:Nucleophilic addition reactions|*]]
[[Category:Reaction mechanisms]]