Editing Addition reaction

{{Short description|Organic reaction in which 2+ molecules combine to form a larger one}}

In [[organic chemistry]], an '''addition reaction''' is an [[organic reaction]] in which two or more [[molecule]]s combine to form a larger molecule called the ''[[adduct]]''.<ref>{{cite book |last1=Morrison |first1=R. T. |last2=Boyd |first2=R. N. |title=Organic Chemistry |edition=4th |location=Boston |publisher=Allyn and Bacon |year=1983 |isbn=0-205-05838-8 |url-access=registration |url=https://archive.org/details/organicchemistry04morr }}</ref><ref>{{JerryMarch}}.</ref>
 
An addition reaction is limited to chemical compounds that have [[bond order|multiple bond]]s. Examples include a molecule with a carbon–carbon [[double bond]] (an [[alkene]]) or a [[triple bond]] (an [[alkyne]]). Another example is a compound that has [[Ring (chemistry)|rings]] (which are also considered points of [[Degree of unsaturation|unsaturation]]). A molecule that has carbon—[[heteroatom]] double bonds, such as a [[carbonyl group]] ({{chem2|C\dO}}) or [[imine|imine group]] ({{chem2|C\dN}}), can undergo an addition reaction because its double-bond.

An addition reaction is the reverse of an [[elimination reaction]], in which one molecule divides into two or more molecules. For instance, the [[hydration reaction|hydration]] of an [[alkene]] to an [[Alcohol (chemistry)|alcohol]] is reversed by [[dehydration reaction|dehydration]]. 

There are two main types of [[Chemical polarity|polar]] addition reactions: [[electrophilic addition]] and [[nucleophilic addition]]. Two non-polar addition reactions exist as well, called [[free-radical addition]] and [[cycloaddition]]s.  Addition reactions are also encountered in polymerizations and called [[addition polymerization]].  

[[File:Addition reactions general overview.svg|frame|center|General overview of addition reactions. Top to bottom: electrophilic addition to alkene, nucleophilic addition of nucleophile to carbonyl and free-radical addition of halide to alkene]]

Depending on the product structure, it could promptly react further to eject a [[leaving group]] to give the [[addition–elimination reaction]] sequence.

Addition reactions are useful in [[analytic chemistry]], as they can identify the existence and number of double bonds in a molecule.  For example, bromine addition will consume a bromine solution, resulting in a color change: 

:<chem display=block>RR'C=CR''R''' + Br2(orange-brown) ->[{}\atop\ce{CCl4}] RR'CBr-BrCR''R'''(typically\ colorless)</chem>  

Likewise [[hydrogenation|hydrogen addition]] often proceeds on all double-bonds of a molecule, and thus gives a count of the number of a double and triple bonds through [[stoichiometry]]:
:<chem display=block>{(H2C=CH)2} + 2H2 ->[{}\atop\ce{Pt}/\ce{Pd}] (H3C-CH2)2</chem>

==References==
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==External links==
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{{Reaction mechanisms}}
{{Organic reactions}}

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[[Category:Addition reactions| ]]
[[Category:Reaction mechanisms]]