SN2 reaction: Difference between revisions

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== S<sub>N</sub>2-Substitution of chloride and methanol ==
==S<sub>N</sub>2-substitution of chloride and methanol==
<StructureSection load='' size='340' side='right' caption='' scene='54/542286/Side_view/2'>
SN2 reaction is a basic reaction type in organic chemistry. The letter S<sub>N</sub> stand for nulceophilic Substitution, the number 2 stands for bimolecular. This means that both reactions partners are involved in the reaction rate determining step. It also exists an S<sub>N</sub>1 reaction; here, only one reaction partner is involved in this step.


On the other side, SN2 reactions are characterised for exchanging substituents. The substituent that leaves the molecule is called leaving group.
<jmol><jmolApplet>
<float>right</float>
<color>gainsboro</color>
<uploadedFileContents>Sn2_for_Veronika.xyz</uploadedFileContents>
<script>dots off; wireframe 30; spacefill 90; label off;</script>


<script>rotate 90; zoom 0; zoom 95.; spacefill on; dots on; spacefill 25%; set antialiasDisplay ON</script>


Typically, alkanes with a substituent in primary position undergo S<sub>N</sub>2 reactions. In contrast to a S<sub>N</sub>1 reaction, no stable carbo cation can be formed. Therefore, another way will be taken.
<caption>SN2 - Substitution of Cl&lt;sup>-&lt;/sup> and Methanol</caption>
The S<sub>N</sub>2 <jmol><jmolLink><script>anim mode once; frame range 1 10; delay 0.5; frame play</script><text>reaction starts</text></jmolLink></jmol> by establishing a so called intermediate state.  This means that both educts come close to each other. By this, the bond of the leaving group is partly broken, and the bond to the new group is partly formed. The formation of this intermediate state is the rate determining step of the reaction.
<controls>spin quality popup labels</controls>
In the <jmol><jmolLink><script>anim mode once; frame range 11 20; delay 0.5; frame play</script><text>second step</text></jmolLink></jmol>, the bond of the leaving group is completely broken, and at the same time the bond to the new substituent is completely formed.
</jmolApplet></jmol>


[[Image:reaction_scheme_sn2.jpg|500px]]
SN2 reaction is a basic reaction type in organic chemistry. The letter S<sub>N</sub> stands for nulceophilic Substitution, the number 2 stands for bimolecular, with both reactions partners are involved in the reaction rate determining step. It also exists an S<sub>N</sub>1 reaction; here, only one reaction partner is involved in this step. On the other side, SN2 reactions are characterized by exchanging substituents. The substituent that leaves the molecule is called leaving group.


The S<sub>N</sub>2 reaction has a very interesting stereochemistry.
Typically, alkanes with a substituent in primary position undergo S<sub>N</sub>2 reactions. In contrast to a S<sub>N</sub>1 reaction, no stable carbo cation can be formed, therefore, another way is taken.
inversion of the stereocenter...
The S<sub>N</sub>2 <jmol><jmolLink><script>anim mode once; frame range 1 10; delay 0.5; frame play</script><text>reaction starts</text></jmolLink></jmol> by establishing a so called ''intermediate'' state, with both educts comeing close to each other. By this, the bond of the leaving group is partly broken, and the bond to the new group is partly formed. The formation of this intermediate state is the rate determining step of the reaction.
In the <jmol><jmolLink><script>anim mode once; frame range 11 20; delay 0.5; frame play</script><text>second step</text></jmolLink></jmol>, the bond of the leaving group is completely broken, and at the same time the bond to the new substituent is completely formed.
[[Image:reaction_scheme_sn2.jpg|450px]] <br>
The S<sub>N</sub>2 reaction has a very interesting stereochemistry inversion of the stereocenter<ref>PMID: 27505286 </ref> with an animated example of the substitution of chloride and methanol shown. Please click on the buttons below to '''animate''' the reaction with different representations. Use the '''popup''' button to enlarge the view and the '''quality''' button to turn on anti-aliasing.


<jmol>
<jmol>
<jmolButton><script>frame 1</script><text>First</text></jmolButton>
<jmolButton><script>frame 1</script><text>First</text></jmolButton>
<jmolButton><script>frame prev</script><text>Previous</text></jmolButton>
<jmolButton><script>frame prev</script><text>Previous</text></jmolButton>
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</jmol>
</jmol>


This demo was adapted from http://www.chemieunterricht-interaktiv.de/en/animations/sn2_substitution/sn2_substitution_3d.html by Dr. V. Pietzner, part of the ChiLe project
<jmol>
<jmolButton><script>spacefill 90; dots on; wireframe 30;</script><text>translucent atoms</text></jmolButton>
<jmolButton><script>spacefill on; dots off;</script><text>spacefilling atoms</text></jmolButton>
<jmolButton><script>spacefill 90; dots off; wireframe 30;</script><text>backbone</text></jmolButton>
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The animation was originally done by [[User:Verena Pietzner | Prof. Dr. Verena Pietzner]]; for details, see her web site ChiLe<ref>[http://www.chemieunterricht-interaktiv.de/en/index.html ChiLe Web Site]</ref>. The implementation into Proteopedia was done by [[User:Jaime Prilusky | Prof. Jaime Prilusky]], [[User:Joel L. Sussman | Prof. Joel L. Sussman ]] 
and [[User:Veronika Pelekhov | Veronika Pelekhov]].


===See also===
===See also===
[[SN1_reaction|S<sub>N</sub>1 reaction: Substitution of Cl<sup>&minus;</sup> and ''tert''-Butanol ]]
[[SN1_reaction|S<sub>N</sub>1 reaction: Substitution of Cl<sup>&minus;</sup> and ''tert''-Butanol ]]<br>
</StructureSection>
[[Esterification|Esterification]]<br>
[[Ozonolysis|Ozonolysis - a type of cycloaddition]]
 
== References ==
== References ==
<references/>
<references/>
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