Editing Carbonyl group (section)

==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>