Editing Organic reaction

{{Short description|Chemical reactions involving organic compounds}}
'''Organic reactions''' are [[chemical reaction]]s involving [[organic compound]]s.<ref>''Strategic Applications of Named Reactions in Organic Synthesis'' Laszlo Kurti, Barbara Czako Academic Press (March 4, '''2005''') {{ISBN|0-12-429785-4}}</ref><ref>J. Clayden, N. Greeves & S. Warren "Organic Chemistry" (Oxford University Press, 2012)</ref><ref>Robert T. Morrison, Robert N. Boyd, and Robert K. Boyd, Organic Chemistry, 6th edition, Benjamin Cummings, 1992</ref> The basic [[organic chemistry]] reaction types are [[addition reaction]]s, [[elimination reaction]]s, [[substitution reaction]]s, [[pericyclic reaction]]s, [[rearrangement reaction]]s, [[mechanistic organic photochemistry|photochemical reactions]] and [[organic redox reaction|redox reactions]]. In [[organic synthesis]], organic reactions are used in the construction of new organic molecules. The production of many man-made chemicals such as drugs, [[plastics]], [[food additives]], [[fabrics]] depend on organic reactions.

The oldest organic reactions are [[combustion]] of organic fuels and [[saponification]] of fats to make soap. Modern [[organic chemistry]] starts with the [[Wöhler synthesis]] in 1828. In the history of the [[Nobel Prize in Chemistry]] awards have been given for the invention of specific organic reactions such as the [[Grignard reaction]] in 1912, the [[Diels–Alder reaction]] in 1950, the [[Wittig reaction]] in 1979 and [[olefin metathesis]] in 2005.

[[Image:Claisen rearrangement scheme.svg|thumb|400px|{{center|The Claisen rearrangement}}]]

==Classifications==
Organic chemistry has a strong tradition of naming a specific reaction to its inventor or inventors and a long '''[[List of organic reactions|list]]''' of so-called '''[[named reaction]]s''' exists, conservatively estimated at 1000. A very old named reaction is the [[Claisen rearrangement]] (1912) and a recent named reaction is the [[Bingel reaction]] (1993). When the named reaction is difficult to pronounce or very long as in the [[Corey–House–Posner–Whitesides reaction]] it helps to use the abbreviation as in the [[CBS reduction]]. The number of reactions hinting at the actual process taking place is much smaller, for example the [[ene reaction]] or [[aldol reaction]].

Another approach to organic reactions is by type of [[organic reagent]], many of them [[inorganic compound|inorganic]], required in a specific transformation. The major types are [[oxidizing agent]]s such as [[osmium tetroxide]], [[reducing agent]]s such as [[lithium aluminium hydride]], [[base (chemistry)|bases]] such as [[lithium diisopropylamide]] and [[acid]]s such as [[sulfuric acid]].

Finally, reactions are also classified by mechanistic class.  Commonly these classes are (1) polar, (2) radical, and (3) pericyclic.  Polar reactions are characterized by the movement of electron pairs from a well-defined source (a [[Nucleophile|nucleophilic]] bond or lone pair) to a well-defined sink (an [[Electrophile|electrophilic]] center with a low-lying antibonding orbital).  Participating atoms undergo changes in charge, both in the formal sense as well as in terms of the actual electron density.  The vast majority of organic reactions fall under this category.  Radical reactions are characterized by species with unpaired electrons ([[Radical (chemistry)|radicals]]) and the movement of single electrons.  Radical reactions are further divided into [[Chain propagation|chain]] and nonchain processes.  Finally, [[pericyclic reaction]]s involve the redistribution of chemical bonds along a cyclic [[transition state]].  Although electron pairs are formally involved, they move around in a cycle without a true source or sink.  These reactions require the continuous overlap of participating orbitals and are governed by [[Woodward–Hoffmann rules|orbital symmetry considerations]].  Of course, some chemical processes may involve steps from two (or even all three) of these categories, so this classification scheme is not necessarily straightforward or clear in all cases.  Beyond these classes, transition-metal mediated reactions are often considered to form a fourth category of reactions, although this category encompasses a broad range of elementary organometallic processes, many of which have little in common and very specific.

==Fundamentals==
Factors governing organic reactions are essentially the same as that of any [[chemical reaction]]. Factors specific to organic reactions are those that determine the stability of reactants and products such as [[Conjugated system|conjugation]], [[hyperconjugation]] and [[aromaticity]] and the presence and stability of [[reactive intermediate]]s such as [[radical (chemistry)|free radical]]s, [[carbocation]]s and [[carbanion]]s.

An organic compound may consist of many [[isomer]]s. Selectivity in terms of [[regioselectivity]], [[diastereoselectivity]] and [[enantioselectivity]] is therefore an important criterion for many organic reactions. The [[stereochemistry]] of [[pericyclic reaction]]s is governed by the [[Woodward–Hoffmann rules]] and that of many [[elimination reaction]]s by  [[Zaitsev's rule]].

Organic reactions are important in the production of [[Medication|pharmaceutical]]s. In a 2006 review,<ref>''Analysis of the reactions used for the preparation of drug candidate molecules'' John S. Carey, David Laffan, Colin Thomson and Mike T. Williams Org. Biomol. Chem., '''2006''', 4, 2337–2347, {{doi|10.1039/b602413k}}</ref> it was estimated that 20% of chemical conversions involved [[alkylation]]s on nitrogen and oxygen atoms, another 20% involved placement and removal of [[protective group]]s, 11% involved formation of new [[carbon–carbon bond]] and 10% involved [[functional group interconversion]]s.

==By mechanism==
There is no limit to the number of possible organic reactions and mechanisms.<ref>Is This Reaction a Substitution, Oxidation–Reduction, or Transfer? / N.S.Imyanitov. J. Chem. Educ. '''1993''', 70(1), 14–16.  {{doi|10.1021/ed070p14}}</ref><ref>March, Jerry (1992), ''Advanced Organic Chemistry: Reactions, Mechanisms, and Structure'' (4th ed.), New York: Wiley, {{ISBN|0-471-60180-2}}</ref> However, certain general patterns are observed that can be used to describe many common or useful reactions. Each reaction has a stepwise [[reaction mechanism]] that explains how it happens, although this detailed description of steps is not always clear from a list of reactants alone. Organic reactions can be organized into several basic types. Some reactions fit into more than one category. For example, some substitution reactions follow an addition-elimination pathway. This overview isn't intended to include every single organic reaction. Rather, it is intended to cover the basic reactions.

{| class="wikitable" style="background-color:white;float: center; border-collapse: collapse;margin: 0em 0em"
!Reaction type
!Subtype
!Comment
|-
|rowspan=3|[[Addition reaction]]s
|[[electrophilic addition]]
|rowspan=3| include such reactions as [[halogenation]], [[hydrohalogenation]] and [[Hydration reaction|hydration]].
|-
|valign=top| [[nucleophilic addition]]
|-
|valign=top| [[radical addition]]
|-
|[[Elimination reaction]]
|
|include processes such as [[dehydration reaction|dehydration]] and are found to follow an E1, E2 or [[E1cB elimination reaction|E1cB]] [[reaction mechanism]]
|-
|rowspan=6|[[Substitution reaction]]s
|[[Nucleophilic substitution|nucleophilic aliphatic substitution]]
|with [[SN1 reaction|S<sub>N</sub>1]], [[SN2 reaction|S<sub>N</sub>2]] and [[SNi|S<sub>N</sub>i]] [[reaction mechanism]]s
|-
|[[nucleophilic aromatic substitution]]
|rowspan=5|
|-
|[[nucleophilic acyl substitution]]
|-
|[[electrophilic substitution]]
|-
|[[electrophilic aromatic substitution]]
|-
|[[radical substitution]]
|-
|[[Organic redox reaction]]s
|
|are [[redox reaction]]s specific to [[organic compound]]s and are very common.
|-
|rowspan=3|[[Rearrangement reaction]]s
|[[1,2-rearrangement]]s
|rowspan=3|
|-
|[[pericyclic|pericyclic reactions]]
|-
|[[olefin metathesis|metathesis]]
|}

In [[condensation reaction]]s a small molecule, usually water, is split off when two [[reactant]]s combine in a chemical reaction. The opposite reaction, when water is consumed in a reaction, is called [[hydrolysis]]. Many [[polymerization]] reactions are derived from organic reactions. They are divided into [[addition polymerization]]s and [[step-growth polymerization]]s.

In general the stepwise progression of reaction mechanisms can be represented using [[arrow pushing]] techniques in which curved arrows are used to track the movement of electrons as starting materials transition to intermediates and products.

== By functional groups ==
Organic reactions can be categorized based on the type of [[functional group]] involved in the reaction as a reactant and the functional group that is formed as a result of this reaction. For example, in the [[Fries rearrangement]] the reactant is an [[ester]] and the reaction product an [[Alcohol (chemistry)|alcohol]].

An overview of functional groups with their preparation and reactivity is presented below:

{|align="center" class="wikitable" style="margin: 0em 0em"
!Functional group
!Preparation
!Reactions
|-
|Acid anhydride||[[Acid anhydride#Preparation|preparation]]||[[Acid anhydride#Reactions|reactions]]
|-
|Acyl halides||[[Acyl halide#Preparation|preparation]]||[[Acyl halide#Reactions|reactions]]
|-
|Acyloins||[[Acyloin#Synthesis|preparation]]||[[Acyloin#Reactions|reactions]]
|-
|Alcohols||[[Alcohol (chemistry)|preparation]]||[[Alcohol (chemistry)#Reactions|reactions]]
|-
|Aldehydes||[[Aldehyde#Synthesis|preparation]]||[[Aldehyde#Common reactions|reactions]]
|-
|Alkanes||[[Alkanes#Preparation|preparation]]||[[Alkanes#Reactions|reactions]]
|-
|Alkenes||[[Alkenes#Synthesis|preparation]]||[[Alkenes#Reactions|reactions]]
|-
|Alkyl halides||[[Alkyl halide#Synthesis|preparation]]||[[Haloalkane#Reactions of haloalkanes|reactions]]
|-
|Alkyl nitrites||[[Alkyl nitrites|preparation]]||[[Alkyl nitrites|reactions]]
|-
|Alkynes||[[Alkynes#Synthesis|preparation]]||[[Alkynes#Reactions|reactions]]
|-
|Amides||[[Amide#Amide synthesis|preparation]]||[[Amide#Amide reactions|reactions]]
|-
|Amine oxide||[[Amine oxide#Synthesis|preparation]]||[[Amine oxide#Reactions|reactions]]
|-
|Amines||[[Amine#Synthesis|preparation]]||[[Amine#Reactions|reactions]]
|-
|Arene compounds||[[Aromatic hydrocarbons#Arene synthesis|preparation]]||[[Aromatic hydrocarbons#Arene reactions|reactions]]
|-
|Azides||[[Azide#Organic azides|preparation]]||[[Azide#Organic azides|reactions]]
|-
|Aziridines||[[Aziridines#Synthesis|preparation]]||[[Aziridines#Reactions|reactions]]
|-
|Carboxylic acids||[[Carboxylic acids#Synthesis|preparation]]||[[Carboxylic acids#Reactions|reactions]]
|-
|Cyclopropanes||[[Cyclopropanation|preparation]]||[[Cyclopropane#Reactions|reactions]]
|-
|Diazo compounds||[[Diazo#Diazo synthesis|preparation]]||[[Diazo#Diazo reactions|reactions]]
|-
|Diols||[[Diol#Synthesis of classes of diols|preparation]]||[[Diol#Reactions|reactions]]
|-
|Esters||[[Ester#Ester synthesis|preparation]]||[[Ester#Reactions|reactions]]
|-
|Ethers||[[Ether#Synthesis|preparation]]||[[Ether#Reactions|reactions]]
|-
|Epoxide||[[Epoxide#Synthesis|preparation]]||[[Epoxide#Reactions|reactions]]
|-
|Haloketones||[[Haloketone#Haloketone synthesis|preparation]]||[[Haloketone#Haloketone reactions|reactions]]
|-
|Imines||[[Imine#Imine synthesis|preparation]]||[[Imine#Imine reactions|reactions]]
|-
|Isocyanates||[[Isocyanate#Isocyanate synthesis|preparation]]||[[Isocyanate#Isocyanate reactions|reactions]]
|-
|Ketones||[[Ketone#Synthesis|preparation]]||[[Ketone#Reactions 2|reactions]]
|-
|Lactams||[[Lactam#Synthesis|preparation]]||[[Lactam#Reactions|reactions]]
|-
|Lactones||[[Lactone#Synthesis|preparation]]||[[Lactone#Reactions|reactions]]
|-
|Nitriles||[[Nitrile#Synthesis|preparation]]||[[Nitrile#Reactions|reactions]]
|-
|Nitro compounds||[[Nitro compound#Preparation|preparation]]||[[Nitro compound#Reduction|reactions]]
|-
|Phenols||[[Phenols#Synthesis|preparation]]||[[Phenols#Reactions|reactions]]
|-
|Thiols||[[Thiol#Preparation|preparation]]||[[Thiol#Reactions|reactions]]
|}

==Other classification==
In [[heterocyclic chemistry]], organic reactions are classified by the type of heterocycle formed with respect to ring-size and type of heteroatom. See for instance the chemistry of [[indole]]s. Reactions are also categorized by the change in the carbon framework. Examples are [[ring expansion and ring contraction]], [[homologation reaction]]s, [[polymerization reaction]]s, [[insertion reaction]]s, [[ring-opening reaction]]s and [[ring-closing reaction]]s.

Organic reactions can also be classified by the type of bond to carbon with respect to the element involved. More reactions are found in [[Organosilicon|organosilicon chemistry]], [[organosulfur chemistry]], [[organophosphorus chemistry]] and [[organofluorine chemistry]]. With the introduction of carbon-metal bonds the field crosses over to [[organometallic chemistry]].

==See also==
*[[List of organic reactions]]
*Other chemical reactions: [[Inorganic chemical reaction|inorganic reaction]]s, [[metabolism]], [[Organometallic chemistry|organometallic reaction]]s, [[polymerization reaction]]s.
*[[List of publications in chemistry#Organic chemistry|Important publications in organic chemistry]]

==References==
{{reflist|30em}}

==External links==
*[http://www.synarchive.com/named-reactions/ Organic reactions @ Synarchive.com]
*[https://web.archive.org/web/20041210052445/http://www.chemistry.ohio-state.edu/organic/flashcards/ Organic reaction flashcards from OSU]
*[http://arquivo.pt/wayback/20091011112359/http://orgchem.chem.uconn.edu/namereact/named.html list of named reactions from UConn]
*[https://web.archive.org/web/20061107085444/http://www.organicworldwide.net/reaction/ organic reactions]
*[http://www.study-organic-chemistry.com Study-Organic-Chemistry.com]

{{Organic reactions}}
{{Organic chemistry}}
{{ChemicalBondsToCarbon}}
{{Branches of chemistry}}
{{Authority control}}

{{DEFAULTSORT:Organic Reaction}}
[[Category:Organic chemistry]]
[[Category:Organic reactions| ]]