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	:[[File:Walden inversion.png\|alt=Walden cycle\|center\|500x500px]]		:[[File:Walden inversion.png\|alt=Walden cycle\|center\|500x500px]]

	In this reaction, the silver oxide in the first step acts as a [[hydroxide]] donor while the silver ion plays no role in the reaction. The intermediates are the carboxyl dianion '''A''' which gives an [[Intramolecular reaction\|intramolecular]] [[nucleophilic substitution]] by the β-carboxylate anion to produce a four-membered β-[[lactone]] ring '''B'''. The α-carboxyl group is also reactive but [[in silico]] data suggests that the [[transition state]] for the formation of the three-membered α-lactone is very high. A hydroxyde ion ring-opens the lactone to form the alcohol '''C''' and the net effect of two counts of inversion is retention of configuration.<ref name="Buchanan Diggle Ruggiero Williams 2006 p=1106">{{cite journal \| ~~last~~=Buchanan \| ~~first~~=J. Grant \| last2=Diggle \| first2=Richard A. \| last3=Ruggiero \| first3=Giuseppe D. \| last4=Williams \| first4=Ian H. \| title=The Walden cycle revisited: a computational study of competitive ring closure to α- and β-lactones \| journal=Chemical Communications \| publisher=Royal Society of Chemistry (RSC) \| issue=10 \| year=2006 \| issn=1359-7345 \| doi=10.1039/b517461a \| ~~page~~=~~1106~~}}</ref>		In this reaction, the silver oxide in the first step acts as a [[hydroxide]] donor while the silver ion plays no role in the reaction. The intermediates are the carboxyl dianion '''A''' which gives an [[Intramolecular reaction\|intramolecular]] [[nucleophilic substitution]] by the β-carboxylate anion to produce a four-membered β-[[lactone]] ring '''B'''. The α-carboxyl group is also reactive but [[in silico]] data suggests that the [[transition state]] for the formation of the three-membered α-lactone is very high. A hydroxyde ion ring-opens the lactone to form the alcohol '''C''' and the net effect of two counts of inversion is retention of configuration.<ref name="Buchanan Diggle Ruggiero Williams 2006 p=1106">{{cite journal \| last1=Buchanan \| first1=J. Grant \| last2=Diggle \| first2=Richard A. \| last3=Ruggiero \| first3=Giuseppe D. \| last4=Williams \| first4=Ian H. \| title=The Walden cycle revisited: a computational study of competitive ring closure to α- and β-lactones \| journal=Chemical Communications \| publisher=Royal Society of Chemistry (RSC) \| issue=10 \| year=2006 \| pages=1106–1108 \| issn=1359-7345 \| doi=10.1039/b517461a \| pmid=16514454 }}</ref>

	== See also ==		== See also ==

imported>Mykhal: chem. typo(gr.)

2025-05-16T17:33:26Z

chem. typo(gr.)

New page

{{short description|Chemical reaction mechanism}}
[[Image:Walden-inversion-3D-balls.png|thumb|right|200px|Montage, using [[ball-and-stick model]]s, of the three steps in an [[SN2 reaction|SN2 reaction]]. The nucleophile is green, the leaving group is red and the three substituents are orange.]]

[[Image:SN2-Walden-before-and-after-horizontal-3D-balls.png|thumb|right|200px|The SN2 reaction causes inversion of stereochemical configuration, known as Walden inversion.]]

'''Walden inversion''' is the inversion of a [[stereocenter|stereogenic]] center in a [[chirality (chemistry)|chiral]] [[molecule]] in a [[chemical reaction]]. Since a molecule can form two [[enantiomer]]s around a stereogenic center, the Walden inversion converts the configuration of the molecule from one enantiomeric form to the other. For example, in an [[SN2 reaction|SN2 reaction]], Walden inversion occurs at a tetrahedral carbon atom. It can be visualized by imagining an [[umbrella]] turned inside-out in a [[gale]]. In the Walden inversion, the backside attack by the nucleophile in an SN2 reaction gives rise to a product whose configuration is opposite to the reactant. Therefore, during SN2 reaction, 100% inversion of product takes place. This is known as Walden inversion.

It was first observed by chemist [[Paul Walden]] in 1896. He was able to convert one enantiomer of a chemical compound into the other enantiomer and back again in a so-called '''Walden cycle''' which went like this: (+)-[[chlorosuccinic acid]] ('''1''' in the illustration) was converted to (+)-[[malic acid]] '''2''' by action of [[silver oxide]] in water with retention of configuration. In the next step the [[hydroxyl]] group was replaced by [[chlorine]] to the other isomer of chlorosuccinic acid '''3''' by reaction with [[phosphorus pentachloride]]. A reaction with silver oxide yielded (−)-malic acid '''4''' and finally a reaction with PCl5 returned the cycle to its starting point.<ref>{{cite journal
| title = Ueber die gegenseitige Umwandlung optischer Antipoden
| author = P. Walden
| journal = [[Berichte der deutschen chemischen Gesellschaft]]
| volume = 29
| issue = 1
| pages = 133–138
| year = 1896
| url = https://zenodo.org/record/1425826
| doi = 10.1002/cber.18960290127 }}</ref>

:[[File:Walden inversion.png|alt=Walden cycle|center|500x500px]]

In this reaction, the silver oxide in the first step acts as a [[hydroxide]] donor while the silver ion plays no role in the reaction. The intermediates are the carboxyl dianion '''A''' which gives an [[Intramolecular reaction|intramolecular]] [[nucleophilic substitution]] by the β-carboxylate anion to produce a four-membered β-[[lactone]] ring '''B'''. The α-carboxyl group is also reactive but [[in silico]] data suggests that the [[transition state]] for the formation of the three-membered α-lactone is very high. A hydroxyde ion ring-opens the lactone to form the alcohol '''C''' and the net effect of two counts of inversion is retention of configuration.<ref name="Buchanan Diggle Ruggiero Williams 2006 p=1106">{{cite journal | last=Buchanan | first=J. Grant | last2=Diggle | first2=Richard A. | last3=Ruggiero | first3=Giuseppe D. | last4=Williams | first4=Ian H. | title=The Walden cycle revisited: a computational study of competitive ring closure to α- and β-lactones | journal=Chemical Communications | publisher=Royal Society of Chemistry (RSC) | issue=10 | year=2006 | issn=1359-7345 | doi=10.1039/b517461a | page=1106}}</ref>

== See also ==
* Another demonstration of the Walden cycle in the [[Brook rearrangement]].

== References ==
{{Reflist}}

{{Authority control}}

[[Category:Substitution reactions]]
[[Category:Reaction mechanisms]]

Walden inversion - Revision history

imported>Fabvill: Add: pmid, pages, authors 1-1. Removed parameters. Some additions/deletions were parameter name changes. | Use this tool. Report bugs. | #UCB_Gadget

imported>Mykhal: chem. typo(gr.)