Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Overview

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

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List of terms related to Functional group

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	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	phenyl-	-benzene	Cumene (2-phenylpropane)
Toluene derivative	Benzyl	RCH₂C₆H₅ RBn	benzyl-	1-(substituent)toluene	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	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 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	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
Carboxylate	Carboxylate	RCOO⁻	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)
Ester	Ester	RCOOR'		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 which contain Nitrogen in this category may contain C-O bonds, such as in the case of amides.

Chemical class	Group	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
Cyanates	Isocyanide	RNC	isocyano-	alkyl isocyanide
Isocyanates	Isocyanate	RNCO	isocyanato-	alkyl isocyanate	Methyl isocyanate
Isocyanates	Isothiocyanate	RNCS	isothiocyanato-	alkyl isothiocyanate	Allyl isothiocyanate
Nitrate	Nitrate	RONO₂	nitrooxy-, nitroxy-	alkyl nitrate	Amyl nitrate (1-nitrooxypentane)
Nitrile	Nitrile	RCN	cyano-	alkanenitrile alkyl cyanide	Benzonitrile (Phenyl cyanide)
Nitrite	Nitrosooxy	RONO	nitrosooxy-	alkyl nitrite	Amyl 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)	-pyridine	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	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-		Glyceraldehyde 3-phosphate
Sulfide or thioether		RSR'		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
Disulfide	Disulfide	RSSR'		alkyl alkyl disulfide	Diphenyl disulfide 1,2-diphenyldisulfane