Functional group
For other uses, see Functional group (disambiguation).
Benzyl acetate has an ester functional group (in red), an acetyl moiety (circled with green) and an benzyl alcohol moiety (circled with orange).
In organic chemistry, functional groups are specific groups of atoms within molecules that are responsible for the characteristic chemical reactions of those molecules. The same functional group will undergo the same or similar chemical reaction(s) regardless of the size of the molecule it is a part of. However, its relative reactivity can be modified by nearby functional groups.
The word moiety is often used synonymously to “functional group”, but according to the IUPAC definition, a moiety is a half of a molecule including substructures of functional groups. For example, an ester is divided into an alcohol and an acyl moiety, but has an ester functional group. The use of the word “moiety” to mean a functional group in the chemistry sense is actually fairly recent. While it has commonly been used in the archeology field to mean the half of a tribal family, it wasn’t until a chance encounter between Elizabeth Bollwerk, an archeology graduate student, and a drug research scientist that the term made the cross-over.
Combining the names of functional groups with the names of the parent alkanes generates a powerful systematic nomenclature for naming organic compounds.
The non-hydrogen atoms of functional groups are always associated with each other and with the rest of the molecule by covalent bonds. When the group of atoms is associated with the rest of the molecule primarily by ionic forces, the group is referred to more properly as a polyatomic ion or complex ion. And all of these are called radicals, by a meaning of the term radical that predates the free radical.
The first carbon atom after the carbon that attaches to the functional group is called the alpha carbon; the second, beta carbon, the third, gamma carbon, etc. If there is another functional group at a carbon, it may be named with the Greek letter, e.g. the gamma-amine in gamma-aminobutanoic acid is on the third carbon of the carbon chain attached to the carboxylic acid group.
Functional groups are attached to the carbon backbone of organic molecules. They determine the characteristics and chemical reactivity of molecules. Functional groups are far less stable than the carbon backbone and are likely to participate in chemical reactions.
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Table of common functional groups
The following is a list of common functional groups. In the formulas, the symbols R and R’ usually denote an attached hydrogen, or a hydrocarbon side chain of any length, but may sometimes refer to any group of atoms.
Hydrocarbons
Functional groups that vary based upon the number and order of π bonds impart different chemistry. Each listing below contains C-H bonds, but each one differs in type (and scope) of reactivity.
Chemical class
Group
Formula
Structural Formula
Prefix
Suffix
Example
Alkane
Alkyl
RH
alkyl-
-ane
Ethane
Alkene
Alkenyl
R2C=CR2
alkenyl-
-ene
Ethylene
(Ethene)
Alkyne
Alkynyl
RC≡CR’
alkynyl-
-yne
Acetylene
(Ethyne)
Benzene derivative
Phenyl
RC6H5
RPh
phenyl-
-benzene
Cumene
(2-phenylpropane)
Toluene derivative
Benzyl
RCH2C6H5
RBn
benzyl-
1-(substituent)toluene
Benzyl bromide
(1-Bromotoluene)
There are also a large number of branched or ring alkanes that have specific names, e.g. tert-butyl, bornyl, cyclohexyl, etc.
Groups containing halogens
Haloalkanes are a class of molecule that is defined by a carbon-halogen bond. This bond can be relatively weak (in the case of an iodoalkane) or quite stable (as in the case of a fluoroalkane). In general, with the exception of fluorinated compounds, haloalkanes readily undergo nucleophilic substitution reactions or elimination reactions. The substitution on the carbon, the acidity of an adjacent proton, the solvent conditions, etc. all can influence the outcome of the reactivity.
Chemical class
Group
Formula
Structural Formula
Prefix
Suffix
Example
haloalkane
halo
RX
halo-
alkyl halide
Chloroethane
(Ethyl chloride)
fluoroalkane
fluoro
RF
fluoro-
alkyl fluoride
Fluoromethane
(Methyl fluoride)
chloroalkane
chloro
RCl
chloro-
alkyl chloride
Chloromethane
(Methyl chloride)
bromoalkane
bromo
RBr
bromo-
alkyl bromide
Bromomethane
(Methyl bromide)
iodoalkane
iodo
RI
iodo-
alkyl iodide
Iodomethane
(Methyl iodide)
Groups containing oxygen
Compounds that contain C-O bonds each possess differing reactivity based upon the location and hybridization of the C-O bond, owing to the electron-withdrawing effect of sp² hybridized oxygen and the donating effects of sp³ hybridized oxygen.
Chemical class
Group
Formula
Structural Formula
Prefix
Suffix
Example
Acyl halide
Haloformyl
RCOX
haloformyl-
-oyl halide
Acetyl chloride
(Ethanoyl chloride)
Alcohol
Hydroxyl
ROH
hydroxy-
-ol
Methanol
Ketone
Carbonyl
RCOR’
keto-, oxo-
-one
Methyl ethyl ketone
(Butanone)
Aldehyde
Aldehyde
RCHO
aldo-
-al
Acetaldehyde
(Ethanal)
Carbonate
Carbonate ester
ROCOOR
alkyl carbonate
carboxy-
-oate
Sodium acetate
(Sodium ethanoate)
Carboxylic acid
Carboxyl
RCOOH
carboxy-
-oic acid
Acetic acid
(Ethanoic acid)
Ether
Ether
ROR’
alkoxy-
alkyl alkyl ether
Diethyl ether
(Ethoxyethane)
alkyl alkanoate
Ethyl butyrate
(Ethyl butanoate)
Hydroperoxide
Hydroperoxy
ROOH
hydroperoxy-
alkyl hydroperoxide
Methyl ethyl ketone peroxide
Peroxide
Peroxy
ROOR
peroxy-
alkyl peroxide
Di-tert-butyl peroxide
Groups containing nitrogen
Compounds that contain Nitrogen in this category may contain C-O bonds, such as in the case of amides.
Chemical class
Group
Formula
Structural Formula
Prefix
Suffix
Example
Amide
Carboxamide
RCONR2
carboxamido-
-amide
Acetamide
(Ethanamide)
Amines
Primary amine
RNH2
amino-
-amine
Methylamine
(Methanamine)
Secondary amine
R2NH
amino-
-amine
Dimethylamine
Tertiary amine
R3N
amino-
-amine
Trimethylamine
4° ammonium ion
R4N+
ammonio-
-ammonium
Choline
Imine
Primary ketimine
RC(=NH)R’
imino-
-imine
Secondary ketimine
RC(=NR)R’
imino-
-imine
Primary aldimine
RC(=NH)H
imino-
-imine
Secondary aldimine
RC(=NR’)H
imino-
-imine
Imide
Imide
RC(=O)NC(=O)R’
imido-
-imide
Azide
Azide
RN3
azido-
alkyl azide
Phenyl azide
(Azidobenzene)
Azo compound
Azo
(Diimide)
RN2R’
azo-
-diazene
Methyl orange
(p-dimethylamino-azobenzenesulfonic acid)
Cyanates
Cyanate
ROCN
cyanato-
alkyl cyanate
Isocyanide
RNC
isocyano-
alkyl isocyanide
Isocyanates
Isocyanate
RNCO
isocyanato-
alkyl isocyanate
Methyl isocyanate
Isothiocyanate
RNCS
isothiocyanato-
alkyl isothiocyanate
Allyl isothiocyanate
Nitrate
Nitrate
RONO2
nitrooxy-, nitroxy-
alkyl nitrate
Amyl nitrate
(1-nitrooxypentane)
alkanenitrile
alkyl cyanide
Nitrite
Nitrosooxy
RONO
nitrosooxy-
alkyl nitrite
Isoamyl nitrite
(3-methyl-1-nitrosooxybutane)
Nitro compound
Nitro
RNO2
nitro-
Nitromethane
Nitroso compound
Nitroso
RNO
nitroso-
Nitrosobenzene
Pyridine derivative
Pyridyl
RC5H4N
4-pyridyl
(pyridin-4-yl)
3-pyridyl
(pyridin-3-yl)
2-pyridyl
(pyridin-2-yl)
Groups containing phosphorus and sulfur
Compounds that contain sulfur and phosphorus exhibit unique chemistry due to their ability to form more bonds than nitrogen and oxygen, their lighter analogues on the periodic table.
Chemical class
Group
Formula
Structural Formula
Prefix
Suffix
Example
Phosphine
Phosphino
R3P
phosphino-
-phosphane
Methylpropylphosphane
Phosphodiester
Phosphate
HOPO(OR)2
phosphoric acid di(substituent) ester
di(substituent) hydrogenphosphate
DNA
Phosphonic acid
Phosphono
RP(=O)(OH)2
phosphono-
substituent phosphonic acid
Benzylphosphonic acid
Phosphate
Phosphate
ROP(=O)(OH)2
phospho-
Sulfide or thioether
di(substituent) sulfide
Dimethyl sulfide
Sulfone
Sulfonyl
RSO2R’
sulfonyl-
di(substituent) sulfone
Dimethyl sulfone
(Methylsulfonylmethane)
Sulfonic acid
Sulfo
RSO3H
sulfo-
substituent sulfonic acid
Benzenesulfonic acid
Sulfoxide
Sulfinyl
RSOR’
sulfinyl-
di(substituent) sulfoxide
Diphenyl sulfoxide
Thiol
Sulfhydryl
RSH
mercapto-, sulfanyl-
-thiol
Ethanethiol
(Ethyl mercaptan)
Thiocyanate
Thiocyanate
RSCN
thiocyanato-
alkyl thiocyanate
alkyl alkyl disulfide
Diphenyl disulfide
1,2-diphenyldisulfane
Other
- For a list of all functional groups: Category:Functional groups
References
- ^ Compendium of Chemical Terminology (IUPAC “Gold Book”) http://goldbook.iupac.org/F02555.html
- ^ March, Jerry (1985). Advanced Organic Chemistry, Reactions, Mechanisms and Structure, third Edition, John Wiley & Sons. ISBN 0-471-85472-7.
- ^ Schleselmann, L. (2004), Pharmacy Times, “Pharmacological History Notes”, http://www.pharmacytimes.com/issues/articles/2004-06_121.asp accessed 5/1/08
External links
- IUPAC Blue Book (organic nomenclature)
- IUPAC ligand abbreviations (pdf)
- Organic Chemistry Help: Functional Groups Flashcards
Functional groups
Chemical class: Alcohol • Aldehyde • Alkane • Alkene • Alkyne • Amide • Amine • Azo compound • Benzene derivative • Carboxylic acid • Cyanate • Disulfide • Ester • Ether • Haloalkane • Hydrazone • Imine • Isocyanide • Isocyanate • Ketone • Oxime • Nitrile • Nitro compound • Nitroso compound • Peroxide • Phosphoric acid • Pyridine derivative • Sulfone • Sulfonic acid • Sulfoxide • Thioester • Thioether • Thiol
Concepts in organic chemistry
Aromaticity, Covalent bonding, Functional groups, Nomenclature, Organic compounds, Organic reactions, Organic synthesis, Publications, Spectroscopy, Stereochemistry, List of organic compounds
Retrieved from “http://en.wikipedia.org/wiki/Functional_group”
Categories: Functional groups | Organic compounds