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{{Short description|Addition reaction of carbonyl compounds and cyanide}}
{{Use dmy dates|date=May 2013}}
{{Use dmy dates|date=January 2024}}
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A '''cyanohydrin reaction''' is an [[organic reaction|organic chemical reaction]] by an [[aldehyde]] or [[ketone]] with a [[cyanide]] [[anion]] or a [[nitrile]] to form a [[cyanohydrin]]. This [[nucleophilic addition]] is a [[reversible reaction]] but with [[aliphatic]] [[carbonyl]] compounds equilibrium is in favor of the reaction products. The cyanide source can be potassium cyanide, [[sodium cyanide]] or [[trimethylsilyl cyanide]]. With aromatic aldehydes such as [[benzaldehyde]], the [[benzoin condensation]] is a competing reaction. The reaction is used in [[carbohydrate chemistry]] as a chain extension method for example that of D-[[xylose]].
{{Reactionbox
| Name = Cyanohydrin reaction
| Type = Addition reaction
| NamedAfter = Friedrich Urech
}}

In [[organic chemistry]], a '''cyanohydrin reaction''' is an [[organic reaction]] in which an [[aldehyde]] ({{chem2|\sCH\dO}}) or [[ketone]] ({{chem2|>C\dO}}) reacts with a [[cyanide]] [[anion]] ({{chem2|N\tC-}}) or a [[nitrile]] ({{chem2|\sC\tN}}) to form a [[cyanohydrin]] ({{chem2|>C(OH)C\tN}}). For example:

<math chem display=block>
\ce{R}{\color{red} \ce{CH=O}} + \ce{R}{\color{purple} \ce{C#N}} \longrightarrow \ce{R2}{\color{red} \ce{C(OH)}}{\color{purple} \ce{C#N}}
</math>

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This [[nucleophilic addition]] is a [[reversible reaction]] but with [[aliphatic]] [[carbonyl]] compounds equilibrium is in favor of the reaction products. The cyanide source can be [[potassium cyanide]] (KCN), [[sodium cyanide]] (NaCN) or [[trimethylsilyl cyanide]] ({{chem2|(CH3)3SiCN}}). With aromatic aldehydes such as [[benzaldehyde]], the [[benzoin condensation]] is a competing reaction. The reaction is used in [[carbohydrate chemistry]] as a chain extension method for example that of D-[[xylose]].


== Examples ==
== Examples ==
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[[Image:Benzoquinone cyanohydrin reaction.svg|thumb|600px|center|Reaction of [[benzoquinone]] with trimethylsilylcyanide, catalyst KCN is introduced as a 1:1 complex with the [[Crown ether]] 18-crown-6]]
[[Image:Benzoquinone cyanohydrin reaction.svg|thumb|600px|center|Reaction of [[benzoquinone]] with trimethylsilylcyanide, catalyst KCN is introduced as a 1:1 complex with the [[Crown ether]] 18-crown-6]]


[[Image:Xylose cyanohydrin reaction.svg|thumb|800px|center|chain extension of D-[[xylose]] in equilibrium with its [[hemiacetal]] with KCN to the cyclic [[ester]]]]


== Reaction mechanism ==
== Reaction mechanism ==
<center>[[Image:Cyanohydrin-mechanism-2D.png|400px|Mechanism of the cyanohydrin reaction]]</center>
[[Image:Cyanohydrin-mechanism-2D.png|400px|center|Mechanism of the cyanohydrin reaction]]


== Asymmetric synthesis ==
== Asymmetric synthesis ==
The [[asymmetric synthesis|asymmetric]] cyanohydrin reaction of [[benzaldehyde]] with trimethylsilylcyanide is made possible by employment of (R)-[[Binol]]<ref>''Chiral Lithium Binaphtholate Aqua Complex as a Highly Effective Asymmetric Catalyst for Cyanohydrin Synthesis'' Manabu Hatano, Takumi Ikeno, Takashi Miyamoto, and Kazuaki Ishihara [[J. Am. Chem. Soc.]]; '''2005'''; 127(31) pp 10776–77 [http://pubs.acs.org/cgi-bin/abstract.cgi/jacsat/2005/127/i31/abs/ja051125c.html Abstract] [http://pubs.acs.org/subscribe/journals/jacsat/suppinfo/ja051125c/ja051125csi20050627_072816.pdf Support info plus proposed transition state]</ref> at 1–10% [[catalyst]] loading. This [[ligand]] firsts reacts with a lithium alkoxy compound to form a lithium binaphtholate Complex.
The [[asymmetric synthesis|asymmetric]] cyanohydrin reaction of [[benzaldehyde]] with trimethylsilylcyanide is made possible by employment of (R)-[[Binol]]<ref>{{cite journal |title=Chiral Lithium Binaphtholate Aqua Complex as a Highly Effective Asymmetric Catalyst for Cyanohydrin Synthesis |first1=Manabu |last1=Hatano |first2=Takumi |last2=Ikeno |first3=Takashi |last3=Miyamoto |first4=Kazuaki |last4=Ishihara |journal=[[J. Am. Chem. Soc.]] |year=2005 |volume=127 |issue=31 |pages=10776–77 |doi=10.1021/ja051125c|pmid=16076152 }}</ref> at 1–10% [[catalyst]] loading. This [[ligand]] firsts reacts with a lithium alkoxy compound to form a lithium binaphtholate Complex.


[[Image:Asymetric cyanohydrin reaction.gif|center|Asymmetric reaction of benzaldehyde with (R)–[[Binol]]–lithium(i-propyloxy) gives (S)-cyanohydrin with 98% [[Enantiomer|ee]]]]
[[Image:Asym cyanohydrin reaction.svg|center|Asymmetric reaction of benzaldehyde with (R)–[[Binol]]–lithium(i-propyloxy) gives (S)-acetonitrile with 98% [[Enantiomer|ee]]]]


<center><small>Asymmetric reaction of benzaldehyde with (R)–[[Binol]]–lithium(i-propyloxy) gives (S)-cyanohydrin with 98% [[Enantiomer|ee]] </small> </center>
{{center|<small>Asymmetric reaction of benzaldehyde with (R)–[[Binol]]–lithium(i-propyloxy) gives (S)-acetonitrile with 98% [[Enantiomer|ee]] </small>}}


The chemist Urech in 1872 was the first to synthesize cyanohydrins from ketones with alkali cyanides and acetic acid<ref>Urech, Ann. 164, 256 ('''1872''')</ref> and therefore this reaction also goes by the name of '''Urech cyanohydrin method'''. With HCN in acidic conditions – i.e. the cyanohydrin is the functional group CN–C–OH
The chemist Urech in 1872 was the first to synthesize cyanohydrins from ketones with alkali cyanides and acetic acid<ref>{{ cite journal| last1=Urech |first1=Friedrich |title=Ueber einige Cyanderivate des Acetons |journal=[[Liebigs Ann.]] |volume=164 |page=255 |year=1872 |issue=2 |doi=10.1002/jlac.18721640207|url=https://zenodo.org/record/1427311 }}</ref> and therefore this reaction also goes by the name of '''Urech cyanohydrin method'''.

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== External links ==
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* Cyanohydrin reaction of [[formaldehyde]] to hydroxyacetonitrile or glycolonitrile with sodium cyanide in [[Organic Syntheses]] Coll. Vol. 2, p.&nbsp;387; Vol. 13, p.&nbsp;56 [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv2p0387 Article]
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* Cyanohydrin reaction of [[formaldehyde]] with potassium cyanide [[Organic Syntheses]] Coll. Vol. 3, p.&nbsp;436; Vol. 27, p.&nbsp;41 [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0436 Article]
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* Cyanohydrin reaction of [[acetophenone]] with potassium cyanide [[Organic Syntheses]] Coll. Vol. 4, p.&nbsp;58; Vol. 33, p.&nbsp;7 [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0058 Article]
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* Cyanohydrin reaction of D-[[xylose]] with potassium cyanide [[Organic Syntheses]] Coll. Vol. 4, p.&nbsp;506; Vol. 36, p.&nbsp;38 [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0506 Article]
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* Cyanohydrin reaction of [[acetone]] with potassium cyanide [[Organic Syntheses]] Coll. Vol. 2, p.&nbsp;7; Vol. 15, p.&nbsp;1 [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv2p0007 Article]
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* Cyanohydrin reaction of [[benzoquinone]] with trimethylsilylcyanide [[Organic Syntheses]] Coll. Vol. 7, p.&nbsp;517; Vol. 60, p.&nbsp;126 [http://www.orgsyn.org/orgsyn/prep.asp?prep=cv7p0517 Article]


== References ==
== References ==
{{reflist}}
{{reflist}}
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== External links ==

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* Cyanohydrin reaction of [[formaldehyde]] to hydroxyacetonitrile or glycolonitrile with sodium cyanide in [[Organic Syntheses]] Coll. Vol. 2, p.&nbsp;387; Vol. 13, p.&nbsp;56 [https://web.archive.org/web/20120329051302/http://www.orgsyn.org/orgsyn/prep.asp?prep=cv2p0387 Article]
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[[Category:Addition reactions]]
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* Cyanohydrin reaction of [[formaldehyde]] with potassium cyanide [[Organic Syntheses]] Coll. Vol. 3, p.&nbsp;436; Vol. 27, p.&nbsp;41 [https://web.archive.org/web/20120329051307/http://www.orgsyn.org/orgsyn/prep.asp?prep=cv3p0436 Article]
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* Cyanohydrin reaction of [[acetophenone]] with potassium cyanide [[Organic Syntheses]] Coll. Vol. 4, p.&nbsp;58; Vol. 33, p.&nbsp;7 [https://web.archive.org/web/20120329051310/http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0058 Article]
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* Cyanohydrin reaction of D-[[xylose]] with potassium cyanide [[Organic Syntheses]] Coll. Vol. 4, p.&nbsp;506; Vol. 36, p.&nbsp;38 [https://web.archive.org/web/20120329051316/http://www.orgsyn.org/orgsyn/prep.asp?prep=cv4p0506 Article]
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* Cyanohydrin reaction of [[acetone]] with potassium cyanide [[Organic Syntheses]] Coll. Vol. 2, p.&nbsp;7; Vol. 15, p.&nbsp;1 [https://web.archive.org/web/20121022154058/http://www.orgsyn.org/orgsyn/prep.asp?prep=cv2p0007 Article]
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* Cyanohydrin reaction of [[benzoquinone]] with trimethylsilylcyanide [[Organic Syntheses]] Coll. Vol. 7, p.&nbsp;517; Vol. 60, p.&nbsp;126 [https://web.archive.org/web/20120329051335/http://www.orgsyn.org/orgsyn/prep.asp?prep=cv7p0517 Article]
{{Organic reactions}}
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[[Category:Nucleophilic addition reactions]]
[[Category:Carbohydrate chemistry]]
[[Category:Carbohydrate chemistry]]
[[Category:Cyanohydrins]]
[[Category:Cyanohydrins]]

Latest revision as of 10:00, 24 October 2024

Cyanohydrin reaction
Named after Friedrich Urech
Reaction type Addition reaction

In organic chemistry, a cyanohydrin reaction is an organic reaction in which an aldehyde (−CH=O) or ketone (>C=O) reacts with a cyanide anion (N≡C−) or a nitrile (−C≡N) to form a cyanohydrin (>C(OH)C≡N). For example:

This nucleophilic addition is a reversible reaction but with aliphatic carbonyl compounds equilibrium is in favor of the reaction products. The cyanide source can be potassium cyanide (KCN), sodium cyanide (NaCN) or trimethylsilyl cyanide ((CH3)3SiCN). With aromatic aldehydes such as benzaldehyde, the benzoin condensation is a competing reaction. The reaction is used in carbohydrate chemistry as a chain extension method for example that of D-xylose.

Examples

[edit]
Reaction of acetone with sodium cyanide to hydroxyacetonitrile
Reaction of benzoquinone with trimethylsilylcyanide, catalyst KCN is introduced as a 1:1 complex with the Crown ether 18-crown-6


Reaction mechanism

[edit]
Mechanism of the cyanohydrin reaction
Mechanism of the cyanohydrin reaction

Asymmetric synthesis

[edit]

The asymmetric cyanohydrin reaction of benzaldehyde with trimethylsilylcyanide is made possible by employment of (R)-Binol[1] at 1–10% catalyst loading. This ligand firsts reacts with a lithium alkoxy compound to form a lithium binaphtholate Complex.

Asymmetric reaction of benzaldehyde with (R)–Binol–lithium(i-propyloxy) gives (S)-acetonitrile with 98% ee
Asymmetric reaction of benzaldehyde with (R)–Binol–lithium(i-propyloxy) gives (S)-acetonitrile with 98% ee
Asymmetric reaction of benzaldehyde with (R)–Binol–lithium(i-propyloxy) gives (S)-acetonitrile with 98% ee

The chemist Urech in 1872 was the first to synthesize cyanohydrins from ketones with alkali cyanides and acetic acid[2] and therefore this reaction also goes by the name of Urech cyanohydrin method.

References

[edit]
  1. ^ Hatano, Manabu; Ikeno, Takumi; Miyamoto, Takashi; Ishihara, Kazuaki (2005). "Chiral Lithium Binaphtholate Aqua Complex as a Highly Effective Asymmetric Catalyst for Cyanohydrin Synthesis". J. Am. Chem. Soc. 127 (31): 10776–77. doi:10.1021/ja051125c. PMID 16076152.
  2. ^ Urech, Friedrich (1872). "Ueber einige Cyanderivate des Acetons". Liebigs Ann. 164 (2): 255. doi:10.1002/jlac.18721640207.
[edit]
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