Carbonyl group#Carbonyl compounds

{{see also|α,β-Unsaturated carbonyl compound}}

In organic chemistry, a carbonyl group characterizes the following types of compounds:

File:Carbon dioxide.svg

Other organic carbonyls are urea and the carbamates, the derivatives of acyl chlorides, chloroformates and phosgene, carbonate esters, thioesters, lactones, lactams, hydroxamates, and isocyanates. 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.

For organic compounds, the length of the C–O bond does not vary widely from 120 picometers. Inorganic carbonyls have shorter C–O distances: CO, 113; CO₂, 116; and COCl₂, 116 pm.{{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}}

The carbonyl carbon is typically electrophilic. A qualitative order of electrophilicity is RCHO (aldehydes) > R₂CO (ketones) > RCO₂R' (esters) > RCONH₂ (amides). A variety of nucleophiles attack, breaking the carbon-oxygen double bond.

Interactions between carbonyl groups and other substituents were found in a study of collagen.{{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}} Substituents can affect carbonyl groups by addition or subtraction of electron density by means of a sigma bond.{{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}} ΔHσ values are much greater when the substituents on the carbonyl group are more electronegative than carbon.

File:Carbonylgruppe.svg

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 double bond, and leading to 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.{{Cite journal |last1=Lienhard |first1=Gustav E. |last2=Jencks |first2=William P. |date=September 1966 |title=Thiol Addition to the Carbonyl Group. Equilibria and Kinetics¹ |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}} The pK_a values of acetaldehyde and acetone are 16.7 and 19 respectively,Ouellette, R.J. and Rawn, J.D. "Organic Chemistry" 1st Ed. Prentice-Hall, Inc., 1996: New Jersey. {{ISBN|0-02-390171-3}}

• Infrared spectroscopy: the C=O double bond absorbs infrared light at wavenumbers between approximately 1600–1900 cm⁻¹(5263 nm to 6250 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.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}}. In addition, the ultraviolet-visible spectra of propanone in water gives an absorption of carbonyl at 257 nm.{{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 }}
• Nuclear magnetic resonance: the C=O double-bond exhibits different resonances depending on surrounding atoms, generally a downfield shift. The ¹³C NMR of a carbonyl carbon is in the range of 160–220 ppm.{{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}}

• Carbon–oxygen bond
• Organic chemistry
• Functional group
• Bridging carbonyl
• Electrophilic addition

{{reflist}}

{{Commons category|Carbonyl group}}

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• 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:Functional groups