Editing Carbonyl group

{{Short description|1=Functional group (C=O)}}
{{for multi|carboxyl as a ligand|Metal carbonyl|the web browser|Carbonyl (web browser)}}
[[File:Ketone-general.svg|thumb|right|A ketone compound containing a carbonyl group (C=O)]]
In [[organic chemistry]], a '''carbonyl group''' is a [[functional group]] with the formula {{chem2|C\dO}}, composed of a [[carbon]] [[atom]] [[double bond|double-bonded]] to an [[oxygen]] atom, and it is [[divalent]] at the C atom. It is common to several classes of organic compounds (such as [[aldehydes]], [[ketones]] and [[carboxylic acid]]), as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound.<ref>{{cite book |title=The Carbonyl Group |year=1966 |editor=Saul Patai |isbn=9780470771051 |doi=10.1002/9780470771051|publisher=John Wiley & Sons|series=PATAI'S Chemistry of Functional Groups|volume=1}}{{cite book |title=The Carbonyl Group|year=1970 |editor=Jacob Zabicky |isbn=9780470771228 |doi=10.1002/9780470771228 |publisher=John Wiley & Sons|series=PATAI'S Chemistry of Functional Groups|volume=2}}</ref>

The term carbonyl can also refer to [[carbon monoxide]] as a [[ligand]] in an [[inorganic]] or [[organometallic]] complex (a [[metal carbonyl]], e.g. [[nickel carbonyl]]).

The remainder of this article concerns itself with the organic chemistry definition of carbonyl, such that carbon and oxygen share a double bond.

==Carbonyl compounds==
{{see also|α,β-Unsaturated carbonyl compound}}
In organic chemistry, a carbonyl group characterizes the following types of compounds:

{|class=wikitable
! align="center" |'''Compound'''
|[[Aldehyde]]||[[Ketone]]||[[Carboxylic acid]]||[[Ester|Carboxylate ester]]||[[Amide]]
|-
! align="center" |'''Structure'''
|[[File:Aldehyd - Aldehyde.svg|60px|Aldehyde]]||[[File:Ketone-general.svg|60px|Ketone]]||[[File:Carboxylic-acid.svg|60px|Carboxylic acid]]||[[File:Ester.svg|60px|Ester]]||[[File:Amide-(tertiary).svg|80px|Amide]]
|-
! align="center" |'''General formula'''
|RCHO||RCOR'||RCOOH||RCOOR'|||<nowiki>RCONR'R''</nowiki>
|}

{|class=wikitable
! align="center" |'''Compound'''
|[[Alpha-beta Unsaturated carbonyl compounds#Enones|Enone]]||[[Acyl halide]]||[[Acid anhydride]]||[[Imide]]
|-
! align="center" |'''Structure'''
|[[File:Enone-general.png|90px|Enone]]||[[File:Acyl-halide.svg|60px|Acyl chloride]]||[[File:Acid anhydride general.svg|95px|Acid anhydride]]||[[File:Imide-general.png|95px|Imide]]
|-
! align="center" |'''General formula'''
|<nowiki>RC(O)C(R')CR''R'''</nowiki>||RCOX||(RCO)<sub>2</sub>O||<nowiki>RC(O)N(R')C(O)R''</nowiki>
|}

[[File:Carbon dioxide.svg|thumb|upright=0.8|Carbon dioxide]]
Other organic carbonyls are [[urea]] and the [[carbamate]]s, the derivatives of [[acyl chloride]]s, [[chloroformate]]s and [[phosgene]], [[carbonate ester]]s, [[thioester]]s, [[lactone]]s, [[lactam]]s, [[Hydroxamic acid|hydroxamates]], and [[isocyanate]]s. Examples of inorganic carbonyl compounds are [[carbon dioxide]] and [[carbonyl sulfide]].{{Citation needed|date=January 2021}}

A special group of carbonyl compounds are [[dicarbonyl]] compounds, which can exhibit special properties.

==Structure and reactivity==
For organic compounds, the length of the C–O bond does not vary widely from 120 [[picometer]]s. Inorganic carbonyls have shorter C–O distances: [[carbon monoxide|CO]], 113; [[carbon dioxide|CO<sub>2</sub>]], 116; and [[phosgene|COCl<sub>2</sub>]], 116 pm.<ref>{{cite book |title=The Carbonyl Group|chapter=General and Theoretical Aspects of the Carbonyl Group|author=G. Berthier, J. Serre |year=1966 |editor=Saul Patai |doi=10.1002/9780470771051.ch1|publisher=John Wiley & Sons|series=PATAI'S Chemistry of Functional Groups|volume=1|pages=1–77|isbn=9780470771051}}</ref>

The carbonyl carbon is typically [[electrophile|electrophilic]].  A qualitative order of electrophilicity is RCHO (aldehydes) > R<sub>2</sub>CO (ketones) > RCO<sub>2</sub>R' (esters) > RCONH<sub>2</sub> (amides).   A variety of nucleophiles attack, breaking the carbon-oxygen [[Pi bond|double bond]].

Interactions between carbonyl groups and other substituents were found in a study of [[collagen]].<ref>{{Cite journal |last1=Newberry |first1=Robert W. |last2=Raines |first2=Ronald T. |date=2017-08-15 |title=The n→π* Interaction |journal=Accounts of Chemical Research |volume=50 |issue=8 |pages=1838–1846 |doi=10.1021/acs.accounts.7b00121 |issn=0001-4842 |pmc=5559721 |pmid=28735540}}</ref> Substituents can affect carbonyl groups by addition or subtraction of electron density by means of a [[sigma bond]].<ref name=":0">{{Cite journal |last=Wiberg |first=Kenneth B. |date=1999-11-01 |title=The Interaction of Carbonyl Groups with Substituents |url=https://pubs.acs.org/doi/10.1021/ar990008h |journal=Accounts of Chemical Research |language=en |volume=32 |issue=11 |pages=922–929 |doi=10.1021/ar990008h |issn=0001-4842}}</ref> Δ''H''σ values are much greater when the substituents on the carbonyl group are more electronegative than carbon.<ref name=":0" />

[[File:Carbonylgruppe.svg|thumb|A carbonyl compound]]

The polarity of C=O bond also enhances the acidity of any adjacent C-H bonds.  Due to the positive charge on carbon and the negative charge on oxygen, carbonyl groups are subject to additions and/or nucleophilic attacks. A variety of nucleophiles attack, breaking the carbon-oxygen [[Pi bond|double bond]], and leading to [[Addition–elimination reaction|addition-elimination reactions]]. Nucleophilic reactivity is often proportional to the basicity of the nucleophile and as nucleophilicity increases, the stability within a carbonyl compound decreases.<ref>{{Cite journal |last1=Lienhard |first1=Gustav E. |last2=Jencks |first2=William P. |date=September 1966 |title=Thiol Addition to the Carbonyl Group. Equilibria and Kinetics<sup>1</sup> |url=http://dx.doi.org/10.1021/ja00969a017 |journal=Journal of the American Chemical Society |volume=88 |issue=17 |pages=3982–3995 |doi=10.1021/ja00969a017 |pmid=5915153 |issn=0002-7863}}</ref> The [[Acid dissociation constant|pK<sub>a</sub>]] values of [[acetaldehyde]] and [[acetone]] are 16.7 and 19 respectively,<ref>Ouellette, R.J. and Rawn, J.D. "Organic Chemistry" 1st Ed.  Prentice-Hall, Inc., 1996: New Jersey.  {{ISBN|0-02-390171-3}}</ref>

==Spectroscopy==

* [[Infrared spectroscopy]]: the C=O double bond absorbs [[infrared]] light at [[wavenumber]]s between approximately 1600&ndash;1900&nbsp;cm<sup>−1</sup>(5263&nbsp;nm to 6250&nbsp;nm). The exact location of the absorption is well understood with respect to the geometry of the molecule. This absorption is known as the "carbonyl stretch" when displayed on an infrared absorption spectrum.<ref>Mayo D.W., Miller F.A and Hannah R.W “Course Notes On The Interpretation of Infrared and Raman Spectra” 1st Ed.  John Wiley & Sons Inc, 2004: New Jersey.  {{ISBN|0-471-24823-1}}.</ref> In addition, the ultraviolet-visible spectra of propanone in water gives an absorption of carbonyl at 257&nbsp;nm.<ref>{{cite web |url=http://media.rsc.org/Modern%20chemical%20techniques/MCT4%20UV%20and%20visible%20spec.pdf |title=Archived copy |access-date=2015-07-11 |url-status=dead |archive-url=https://web.archive.org/web/20150824053622/http://media.rsc.org/Modern%20chemical%20techniques/MCT4%20UV%20and%20visible%20spec.pdf |archive-date=2015-08-24 }}</ref>
* [[Nuclear magnetic resonance]]: the C=O double-bond exhibits different resonances depending on surrounding atoms, generally a downfield shift.  The <sup>13</sup>C NMR of a carbonyl carbon is in the range of 160–220 ppm.<ref>{{cite web |title=NMR Spectroscopy. 13C NMR |url=https://organicchemistrydata.org/hansreich/resources/nmr/?index=nmr_index%2F13C_shift |website=organicchemistrydata.org |access-date=6 January 2024 |archive-url=https://web.archive.org/web/20240106080835/https://organicchemistrydata.org/hansreich/resources/nmr/?index=nmr_index%2F13C_shift |archive-date=6 January 2024 |date=20 October 2021}}</ref>

==See also==
* [[Carbon–oxygen bond]]
* [[Organic chemistry]]
* [[Functional group]]
* [[Bridging carbonyl]]
* [[Electrophilic addition]]

==References==
{{reflist}}

==Further reading==
{{Commons category|Carbonyl group}}
{{wikiquote}}
* L.G. Wade, Jr. ''Organic Chemistry, 5th ed.'' [[Prentice Hall]], 2002. {{ISBN|0-13-033832-X}}
* The [[Frostburg State University]] Chemistry Department. [http://www.chemhelper.com/ Organic Chemistry Help] (2000).
* Advanced Chemistry Development, Inc. [http://www.acdlabs.com/iupac/nomenclature IUPAC Nomenclature of Organic Chemistry] (1997).
* William Reusch. tara [https://web.archive.org/web/20071029211245/http://www.cem.msu.edu/~reusch/VirtualText/intro1.htm VirtualText of Organic Chemistry] (2004).
* Purdue Chemistry Department [http://chemed.chem.purdue.edu/genchem/topicreview/bp/2organic/carbonyl.html] (retrieved Sep 2006).  Includes water solubility data.
* William Reusch. (2004) [https://web.archive.org/web/20020917024512/http://www.cem.msu.edu/~reusch/VirtualText/aldket1.htm Aldehydes and Ketones] Retrieved 23 May 2005.
* ILPI. (2005) [https://web.archive.org/web/20150402093646/http://www.ilpi.com/msds/ref/anhydride.html The MSDS Hyperglossary- Anhydride].
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[[Category:Carbonyl compounds| ]]
[[Category:Functional groups]]