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Dictionary:

functional group


n.

An atom or group of atoms, such as a carboxyl group, that replaces hydrogen in an organic compound and that defines the structure of a family of compounds and determines the properties of the family.


 
 

In molecules, any of numerous combinations of atoms that undergo characteristic chemical reactions themselves and in many cases influence the reactivity of the rest of the molecule. Organic compounds are often classified according to the functional groups they contain. Common functional groups include hydroxyl (-OH), in alcohols and phenols; carboxyl (-COOH), in carboxylic acids; carbonyl (-C=O), in aldehydes, ketones, amides, carboxylic acids, esters, and quinones; and nitro (-NO2) and amino (-NH2), in certain organic nitrogen compounds.

For more information on functional group, visit Britannica.com.

 
Columbia Encyclopedia: functional group,
in organic chemistry, group of atoms within a molecule that is responsible for certain properties of the molecule and reactions in which it takes part. Organic compounds are frequently classified according to the functional group or groups they contain. For example, methanol, ethanol, and isopropanol are all classified as alcohols since each contains a functional hydroxyl group.


 
Medical Dictionary: functional group

n.

An atom or group of atoms, that replaces hydrogen in an organic compound and that defines the structure of a family of compounds and determines the properties of the family.

 
Wikipedia: functional group


In organic chemistry, functional groups (or moieties) 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.

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.

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.

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 which 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 alkyl- -ane methane
Methane
Alkene Alkenyl R2C=CR2 Alkene alkenyl- -ene ethylene
Ethylene
(Ethene)
Alkyne Alkynyl RC≡CR' Alkyne alkynyl- -yne acetylene
Acetylene
(Ethyne)
Benzene derivative Phenyl RC6H5 Phenyl phenyl- -benzene Cumene
Cumene
(2-phenylpropane)
Toluene derivative Benzyl RCH2C6H5
RBn
Benzyl benzyl- 1-(substituent)toluene Benzyl bromide
Benzyl bromide
(1-Bromotoluene)

Groups containing halogens

Haloalkanes are a class of molecule which 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 Halide group halo- alkyl halide Chloroethane
Chloroethane
(Ethyl chloride)
fluoroalkane fluoro RF Fluoro group fluoro- alkyl fluoride Fluoromethane
Fluoromethane
(Methyl fluoride)
chloroalkane chloro RCl Chloro group chloro- alkyl chloride Chloromethane
Chloromethane
(Methyl chloride)
bromoalkane bromo RBr Bromo group bromo- alkyl bromide Bromomethane
Bromomethane
(Methyl bromide)
iodoalkane iodo RI Iodo group iodo- alkyl iodide Iodomethane
Iodomethane
(Methyl iodide)

Groups containing oxygen

Compounds which 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 Acyl halide haloformyl- -oyl halide Acetyl chloride
Acetyl chloride
(Ethanoyl chloride)
Alcohol Hydroxyl ROH Hydroxyl hydroxy- -ol methanol
Methanol
Ketone Carbonyl RCOR' Ketone keto-, oxo- -one Butanone
Methyl ethyl ketone
(Butanone)
Aldehyde Aldehyde RCHO Aldehyde aldo- -al acetaldehyde
Acetaldehyde
(Ethanal)
Carbonate Carbonate ester ROCOOR Carbonate alkyl carbonate
Carboxylate Carboxylate RCOO Carboxylate

Carboxylate

carboxy- -oate Sodium acetate
Sodium acetate
(Sodium ethanoate)
Carboxylic acid Carboxyl RCOOH Carboxylic acid carboxy- -oic acid Acetic acid
Acetic acid
(Ethanoic acid)
Ether Ether ROR' Ether alkoxy- alkyl alkyl ether Diethyl ether
Diethyl ether
(Ethoxyethane)
Ester Ester RCOOR' Ester alkyl alkanoate Ethyl butyrate
Ethyl butyrate
(Ethyl butanoate)
Hydroperoxide Hydroperoxy ROOH Hydroperoxy hydroperoxy- alkyl hydroperoxide Methyl ethyl ketone peroxide
Methyl ethyl ketone peroxide
Peroxide Peroxy ROOR Peroxy peroxy- alkyl peroxide Di-tert-butyl peroxide
Di-tert-butyl peroxide

Groups containing nitrogen

Compounds which 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 Amide carboxamido- -amide acetamide
Acetamide
(Ethanamide)
Amines Primary amine RNH2 Primary amine amino- -amine methylamine
Methylamine
(Methanamine)
Secondary amine R2NH Secondary amine amino- -amine dimethylamine
Dimethylamine
Tertiary amine R3N Tertiary amine amino- -amine trimethylamine
Trimethylamine
4° ammonium ion R4N+ Quaternary ammonium cation ammonio- -ammonium choline
Choline
Imine Primary ketimine RC(=NH)R' Imine imino- -imine
Secondary ketimine RC(=NR)R' Imine imino- -imine
Primary aldimine RC(=NH)H Imine imino- -imine
Secondary aldimine RC(=NR')H Imine imino- -imine
Imide Imide RC(=O)NC(=O)R' Imide imido- -imide
Azide Azide RN3 Organoazide azido- alkyl azide Phenyl azide
Phenyl azide
(Azidobenzene)
Azo compound Azo
(Diimide)
RN2R' Azo.pngl azo- -diazene Methyl orange
Methyl orange
(p-dimethylamino-azobenzenesulfonic acid)
Cyanates Cyanate ROCN Cyanate cyanato- alkyl cyanate
Isocyanide RNC Isocyanide isocyano- alkyl isocyanide
Isocyanates Isocyanate RNCO Isocyanate isocyanato- alkyl isocyanate Methyl isocyanate
Methyl isocyanate
Isothiocyanate RNCS Isothiocyanate isothiocyanato- alkyl isothiocyanate Allyl isothiocyanate
Allyl isothiocyanate
Nitrate Nitrate RONO2 Nitrate nitrooxy-, nitroxy-

alkyl nitrate

Amyl nitrate
Amyl nitrate
(1-nitrooxypentane)
Nitrile Nitrile RCN Nitrile cyano-

alkanenitrile
alkyl cyanide

Benzonitrile
Benzonitrile
(Phenyl cyanide)
Nitrite Nitrosooxy RONO Nitrite nitrosooxy-

alkyl nitrite

Amyl nitrite
Amyl nitrite
(3-methyl-1-nitrosooxybutane)
Nitro compound Nitro RNO2 Nitro nitro-   Nitromethane
Nitromethane
Nitroso compound Nitroso RNO Nitroso nitroso-   Nitrosobenzene
Nitrosobenzene
Pyridine derivative Pyridyl RC5H4N

4-pyridyl group
3-pyridyl group
2-pyridyl group

4-pyridyl
(pyridin-4-yl)

3-pyridyl
(pyridin-3-yl)

2-pyridyl
(pyridin-2-yl)

-pyridine Nicotine
Nicotine

Groups containing phosphorus and sulfur

Compounds which 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 A tertiary phosphine phosphino- -phosphane Methylpropylphosphane
Methylpropylphosphane
Phosphodiester Phosphate HOPO(OR)2 Phosphodiester phosphoric acid di(substituent) ester di(substituent) hydrogenphosphate DNA
Phosphonic acid Phosphono RP(=O)(OH)2 Phosphono group phosphono- substituent phosphonic acid Benzylphosphonic acid
Benzylphosphonic acid
Phosphate Phosphate ROP(=O)(OH)2 Phosphate group phospho- Glyceraldehyde 3-phosphate
Glyceraldehyde 3-phosphate
Sulfide or thioether RSR' Sulfide group di(substituent) sulfide Dimethyl sulfide
Dimethyl sulfide
Sulfone Sulfonyl RSO2R' Sulfonyl group sulfonyl- di(substituent) sulfone Dimethyl sulfone
Dimethyl sulfone
(Methylsulfonylmethane)
Sulfonic acid Sulfo RSO3H Sulfonyl group sulfo- substituent sulfonic acid Benzenesulfonic acid
Benzenesulfonic acid
Sulfoxide Sulfinyl RSOR' Sulfinyl group sulfinyl- di(substituent) sulfoxide Diphenyl sulfoxide
Diphenyl sulfoxide
Thiol Sulfhydryl RSH Sulfhydryl mercapto-, sulfanyl- -thiol Ethanethiol
Ethanethiol
(Ethyl mercaptan)
Thiocyanate Thiocyanate RSCN Thiocyanate thiocyanato- alkyl thiocyanate
Disulfide Disulfide RSSR' Disulfide alkyl alkyl disulfide Diphenyl disulfide
Diphenyl disulfide
1,2-diphenyldisulfane

Other

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Copyrights:

Dictionary. The American Heritage® Dictionary of the English Language, Fourth Edition Copyright © 2007, 2000 by Houghton Mifflin Company. Updated in 2007. Published by Houghton Mifflin Company. All rights reserved.  Read more
Britannica Concise Encyclopedia. Britannica Concise Encyclopedia. © 2006 Encyclopædia Britannica, Inc. All rights reserved.  Read more
Columbia Encyclopedia. The Columbia Electronic Encyclopedia, Sixth Edition Copyright © 2003, Columbia University Press. Licensed from Columbia University Press. All rights reserved. www.cc.columbia.edu/cu/cup/  Read more
Medical Dictionary. The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company Read more
Wikipedia. This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article "Functional group" Read more

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