Functional group (C=O)
For
organic chemistry
, a
carbonyl group
is a
functional group
with the formula
C=O
, composed of a
carbon
atom
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 acids
), as part of many larger functional groups. A compound containing a carbonyl group is often referred to as a carbonyl compound.
[1]
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
[
edit
]
In organic chemistry, a carbonyl group characterizes the following types of compounds:
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
]
A special group of carbonyl compounds are
dicarbonyl
compounds, which can exhibit special properties.
Structure and reactivity
[
edit
]
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;
CO
2
, 116; and
COCl
2
, 116 pm.
[2]
The carbonyl carbon is typically
electrophilic
. A qualitative order of electrophilicity is RCHO (aldehydes) > R
2
CO (ketones) > RCO
2
R' (esters) > RCONH
2
(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
.
[3]
Substituents can affect carbonyl groups by addition or subtraction of electron density by means of a
sigma bond
.
[4]
Δ
H
σ values are much greater when the substituents on the carbonyl group are more electronegative than carbon.
[4]
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
. Nucleophiliic reactivity is often proportional to the basicity of the nucleophile and as nucleophilicity increases, the stability within a carbonyl compound decreases.
[5]
The
pK
a
values of
acetaldehyde
and
acetone
are 16.7 and 19 respectively,
[6]
Spectroscopy
[
edit
]
- 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.
[7]
In addition, the ultraviolet-visible spectra of propanone in water gives an absorption of carbonyl at 257 nm.
[8]
- Nuclear magnetic resonance
: the C=O double-bond exhibits different resonances depending on surrounding atoms, generally a downfield shift. The
13
C NMR of a carbonyl carbon is in the range of 160?220 ppm.
[9]
See also
[
edit
]
References
[
edit
]
- ^
Saul Patai, ed. (1966).
The Carbonyl Group
. PATAI'S Chemistry of Functional Groups. Vol. 1. John Wiley & Sons.
doi
:
10.1002/9780470771051
.
ISBN
9780470771051
.
Jacob Zabicky, ed. (1970).
The Carbonyl Group
. PATAI'S Chemistry of Functional Groups. Vol. 2. John Wiley & Sons.
doi
:
10.1002/9780470771228
.
ISBN
9780470771228
.
- ^
G. Berthier, J. Serre (1966). "General and Theoretical Aspects of the Carbonyl Group". In Saul Patai (ed.).
The Carbonyl Group
. PATAI'S Chemistry of Functional Groups. Vol. 1. John Wiley & Sons. pp. 1?77.
doi
:
10.1002/9780470771051.ch1
.
ISBN
9780470771051
.
- ^
Newberry, Robert W.; Raines, Ronald T. (2017-08-15).
"The n→π* Interaction"
.
Accounts of Chemical Research
.
50
(8): 1838?1846.
doi
:
10.1021/acs.accounts.7b00121
.
ISSN
0001-4842
.
PMC
5559721
.
PMID
28735540
.
- ^
a
b
Wiberg, Kenneth B. (1999-11-01).
"The Interaction of Carbonyl Groups with Substituents"
.
Accounts of Chemical Research
.
32
(11): 922?929.
doi
:
10.1021/ar990008h
.
ISSN
0001-4842
.
- ^
Lienhard, Gustav E.; Jencks, William P. (September 1966).
"Thiol Addition to the Carbonyl Group. Equilibria and Kinetics
1
"
.
Journal of the American Chemical Society
.
88
(17): 3982?3995.
doi
:
10.1021/ja00969a017
.
ISSN
0002-7863
.
PMID
5915153
.
- ^
Ouellette, R.J. and Rawn, J.D. "Organic Chemistry" 1st Ed. Prentice-Hall, Inc., 1996: New Jersey.
ISBN
0-02-390171-3
- ^
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
.
- ^
"Archived copy"
(PDF)
. Archived from
the original
(PDF)
on 2015-08-24
. Retrieved
2015-07-11
.
{{
cite web
}}
: CS1 maint: archived copy as title (
link
)
- ^
"NMR Spectroscopy. 13C NMR"
.
organicchemistrydata.org
. 20 October 2021. Archived from
the original
on 6 January 2024
. Retrieved
6 January
2024
.
Further reading
[
edit
]
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Hydrocarbons
(only C and H)
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Only
carbon
,
hydrogen
,
and
oxygen
(only C, H and O)
| |
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Only one
element,
not being
carbon,
hydrogen,
or oxygen
(one element,
not C, H or O)
| |
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Other
| |
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|