Functional group

For other uses, see Functional group (disambiguation).

Benzyl acetate has an ester functional group (in red), an acetyl moiety (circled with dark green) and a benzyloxy moiety (circled with light orange). Other divisions can be made.

In organic chemistry, functional groups are specific groups (moieties) of atoms or bonds 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.^[1]^[2] However, its relative reactivity can be modified by other functional groups nearby. The atoms of functional groups are linked to each other and to the rest of the molecule by covalent bonds. When the group of covalently bound atoms bears a net charge, the group is referred to more properly as a polyatomic ion or a complex ion. Any subgroup of atoms of a compound also may be called a radical, and if a covalent bond is broken homolytically, the resulting fragment radicals are referred as free radicals.

Combining the names of functional groups with the names of the parent alkanes generates what is termed a systematic nomenclature for naming organic compounds. 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.

Table of common functional groups

The following is a list of common functional groups.^[3] 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, called hydrocarbyl, that contain only carbon and hydrogen, but vary in the number and order of double bonds. Each one differs in type (and scope) of reactivity.

Chemical class	Group	Formula	Structural Formulae	Prefix	Suffix	Example
Alkane	Alkyl	R(CH₂)_nH		alkyl-	-ane	Ethane
Alkene	Alkenyl	R₂C=CR₂		alkenyl-	-ene	Ethylene (Ethene)
Alkyne	Alkynyl	RC≡CR'	${\ce {R-C{\equiv }C-R'}}$	alkynyl-	-yne	${\ce {H-C{\equiv }C-H}}$ Acetylene (Ethyne)
Benzene derivative	Phenyl	RC₆H₅ RPh		phenyl-	-benzene	Cumene (Isopropylbenzene)

There are also a large number of branched or ring alkanes that have specific names, e.g., tert-butyl, bornyl, cyclohexyl, etc. Hydrocarbons may form charged structures: positively charged carbocations or negative carbanions. Carbocations are often named -um. Examples are tropylium and triphenylmethyl cations and the cyclopentadienyl anion.

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	${\ce {R-X}}$	halo-	alkyl halide	Chloroethane (Ethyl chloride)
fluoroalkane	fluoro	RF	${\ce {R-F}}$	fluoro-	alkyl fluoride	Fluoromethane (Methyl fluoride)
chloroalkane	chloro	RCl	${\ce {R-Cl}}$	chloro-	alkyl chloride	Chloromethane (Methyl chloride)
bromoalkane	bromo	RBr	${\ce {R-Br}}$	bromo-	alkyl bromide	Bromomethane (Methyl bromide)
iodoalkane	iodo	RI	${\ce {R-I}}$	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 sp-hybridized oxygen (carbonyl groups) and the donating effects of sp²-hybridized oxygen (alcohol groups).

Chemical class	Group	Formula	Prefix	Suffix	Example
Alcohol	Hydroxyl	ROH	hydroxy-	-ol	Methanol
Ketone	Carbonyl	RCOR'	-oyl- (-COR') or oxo- (=O)	-one	Butanone (Methyl ethyl ketone)
Aldehyde	Aldehyde	RCHO	formyl- (-COH) or oxo- (=O)	-al	Acetaldehyde (Ethanal)
Acyl halide	Haloformyl	RCOX	carbonofluoridoyl- carbonochloridoyl- carbonobromidoyl- carbonoiodidoyl-	-oyl halide	Acetyl chloride (Ethanoyl chloride)
Carbonate	Carbonate ester	ROCOOR	(alkoxycarbonyl)oxy-	alkyl carbonate	Triphosgene (bis(trichloromethyl) carbonate)
Carboxylate	Carboxylate	RCOO⁻	carboxy-	-oate	Sodium acetate (Sodium ethanoate)
Carboxylic acid	Carboxyl	RCOOH	carboxy-	-oic acid	Acetic acid (Ethanoic acid)
Ester	Ester	RCOOR'	alkanoyloxy- or alkoxycarbonyl	alkyl alkanoate	Ethyl butyrate (Ethyl butanoate)
Methoxy	Methoxy	ROCH₃	methoxy-
Hydroperoxide	Hydroperoxy	ROOH	hydroperoxy-	alkyl hydroperoxide	tert-Butyl hydroperoxide
Peroxide	Peroxy	ROOR	peroxy-	alkyl peroxide	Di-tert-butyl peroxide
Ether	Ether	ROR'	alkoxy-	alkyl ether	Diethyl ether (Ethoxyethane)
Hemiacetal	Hemiacetal	RCH(OR')(OH)	alkoxy -ol	-al alkyl hemiacetal
Hemiketal	Hemiketal	RC(ORʺ)(OH)R'	alkoxy -ol	-one alkyl hemiketal
Acetal	Acetal	RCH(OR')(OR")	dialkoxy-	-al dialkyl acetal
Ketal (or Acetal)	Ketal (or Acetal)	RC(ORʺ)(OR‴)R'	dialkoxy-	-one dialkyl ketal
Orthoester	Orthoester	RC(OR')(ORʺ)(OR‴)	trialkoxy-
Heterocycle	Methylenedioxy	PhOCOPh	methylenedioxy-	-dioxole	1,2-Methylenedioxybenzene (1,3-Benzodioxole)
Orthocarbonate ester	Orthocarbonate ester	C(OR)(OR')(ORʺ)(OR″)	tetralkoxy-	tetraalkyl orthocarbonate

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- or carbamoyl-	-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	${\ce {RC(=NR'')R'}}$		imino-	-imine
	Primary aldimine	RC(=NH)H		imino-	-imine	Ethanimine
	Secondary aldimine	RC(=NR')H		imino-	-imine
Imide	Imide	(RCO)₂NR'		imido-	-imide	Succinimide (Pyrrolidine-2,5-dione)
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	Methyl cyanate
Cyanates	Isocyanate	RNCO		isocyanato-	alkyl isocyanate	Methyl isocyanate
Nitrate	Nitrate	RONO₂		nitrooxy-, nitroxy-	alkyl nitrate	Amyl nitrate (1-nitrooxypentane)
Nitrile	Nitrile	RCN	${\ce {R-\!{\equiv }N}}$	cyano-	alkanenitrile alkyl cyanide	Benzonitrile (Phenyl cyanide)
Nitrile	Isonitrile	RNC	${\ce {R-{\overset {+}{N}}{\equiv }C^{-}}}$	isocyano-	alkaneisonitrile alkyl isocyanide	${\ce {H3C-{\overset {+}{N}}{\equiv }C^{-}}}$ Methyl isocyanide
Nitrite	Nitrosooxy	RONO		nitrosooxy-	alkyl nitrite	Isoamyl nitrite (3-methyl-1-nitrosooxybutane)
Nitro compound	Nitro	RNO₂		nitro-		Nitromethane
Nitroso compound	Nitroso	RNO		nitroso- (Nitrosyl-)		Nitrosobenzene
Oxime	Oxime	RCH=NOH			Oxime	Acetone oxime (2-Propanone oxime)
Pyridine derivative	Pyridyl	RC₅H₄N		4-pyridyl (pyridin-4-yl) 3-pyridyl (pyridin-3-yl) 2-pyridyl (pyridin-2-yl)	-pyridine	Nicotine

Groups containing sulfur

Compounds that contain sulfur exhibit unique chemistry due to their ability to form more bonds than oxygen, their lighter analogue on the periodic table. Substitutive nomenclature (marked as prefix in table) is preferred over functional class nomenclature (marked as suffix in table) for sulfides, disulfides, sulfoxides and sulfones.

Chemical class	Group	Formula	Prefix	Suffix	Example
Thiol	Sulfhydryl	RSH	sulfanyl- (-SH)	-thiol	Ethanethiol
Sulfide (Thioether)	Sulfide	RSR'	substituent sulfanyl- (-SR')	di(substituent) sulfide	(Methylsulfanyl)methane (prefix) or Dimethyl sulfide (suffix)
Disulfide	Disulfide	RSSR'	substituent disulfanyl- (-SSR')	di(substituent) disulfide	(Methyldisulfanyl)methane (prefix) or Dimethyl disulfide (suffix)
Sulfoxide	Sulfinyl	RSOR'	-sulfinyl- (-SOR')	di(substituent) sulfoxide	(Methanesulfinyl)methane (prefix) or Dimethyl sulfoxide (suffix)
Sulfone	Sulfonyl	RSO₂R'	-sulfonyl- (-SO₂R')	di(substituent) sulfone	(Methanesulfonyl)methane (prefix) or Dimethyl sulfone (suffix)
Sulfinic acid	Sulfino	RSO₂H	sulfino- (-SO₂H)	-sulfinic acid	2-Aminoethanesulfinic acid
Sulfonic acid	Sulfo	RSO₃H	sulfo- (-SO₃H)	-sulfonic acid	Benzenesulfonic acid
Thiocyanate	Thiocyanate	RSCN	thiocyanato- (-SCN)	substituent thiocyanate	Phenyl thiocyanate
Thiocyanate	Isothiocyanate	RNCS	isothiocyanato- (-NCS)	substituent isothiocyanate	Allyl isothiocyanate
Thione	Carbonothioyl	RCSR'	-thioyl- (-CSR') or sulfanylidene- (=S)	-thione	Diphenylmethanethione (Thiobenzophenone)
Thial	Carbonothioyl	RCSH	methanethioyl- (-CSH) or sulfanylidene- (=S)	-thial
Thioester
carbodithioic acid

Groups containing phosphorus

Compounds that contain phosphorus exhibit unique chemistry due to their ability to form more bonds than nitrogen, their lighter analogues on the periodic table.

Chemical class	Group	Formula	Prefix	Suffix	Example
Phosphine (Phosphane)	Phosphino	R₃P	phosphanyl-	-phosphane	Methylpropylphosphane
Phosphonic acid	Phosphono	${\ce {RP(=O)(OH)2}}$	phosphono-	substituent phosphonic acid	Benzylphosphonic acid
Phosphate	Phosphate	${\ce {ROP(=O)(OH)2}}$	phosphonooxy- or O-phosphono- (phospho-)	substituent phosphate	Glyceraldehyde 3-phosphate (suffix)
Phosphate	Phosphate	${\ce {ROP(=O)(OH)2}}$	phosphonooxy- or O-phosphono- (phospho-)	substituent phosphate	O-Phosphonocholine (prefix) (Phosphocholine)
Phosphodiester	Phosphate	HOPO(OR)₂	[(alkoxy)hydroxyphosphoryl]oxy- or O-[(alkoxy)hydroxyphosphoryl]-	di(substituent) hydrogen phosphate or phosphoric acid di(substituent) ester	DNA
Phosphodiester	Phosphate	HOPO(OR)₂			O‑[(2‑Guanidinoethoxy)hydroxyphosphoryl]‑l‑serine (prefix) (Lombricine)

Groups containing boron

Compounds containing boron exhibit unique chemistry due to their having partially filled octets and therefore acting as Lewis acids.

Chemical class	Group	Formula	Prefix	Suffix	Example
Boronic acid	Borono	RB(OH)₂	Borono-	substituent boronic acid	Phenylboronic acid
Boronic ester	Boronate	RB(OR)₂	O-[bis(alkoxy)alkylboronyl]-	substituent boronic acid di(substituent) ester
Borinic acid	Borino	R₂BOH	Hydroxyborino-	di(substituent) borinic acid
Borinic ester	Borinate	R₂BOR	O-[alkoxydialkylboronyl]-	di(substituent) borinic acid substituent ester	Diphenylborinic acid 2-aminoethyl ester (2-Aminoethoxydiphenyl borate)

Names of radicals or moieties

These names are used to refer to the moieties themselves or to radical species, and also to form the names of halides and substituents in larger molecules.

When the parent hydrocarbon is unsaturated, the suffix ("-yl", "-ylidene", or "-ylidyne") replaces "-ane" (e.g. "ethane" becomes "ethyl"); otherwise, the suffix replaces only the final "-e" (e.g. "ethyne" becomes "ethynyl").^[4]

Note that when used to refer to moieties, multiple single bonds differ from a single multiple bond. For example, a methylene bridge (methanediyl) has two single bonds, whereas a methylene group (methylidene) has one double bond. Suffixes can be combined, as in methylidyne (triple bond) vs. methylylidene (single bond and double bond) vs. methanetriyl (three single bonds).

There are some retained names, such as methylene for methanediyl, 1,x-phenylene for phenyl-1,x-diyl (where x is 2, 3, or 4),^[5] carbyne for methylidyne, and trityl for triphenylmethyl.

Chemical class	Group	Formula	Prefix	Suffix	Example
Single bond		R•	Ylo-^[6]	-yl	Methyl group Methyl radical
Double bond		R:	?	-ylidene	Methylidene
Triple bond		R⫶	?	-ylidyne	Methylidyne
Carboxylic acyl radical	Acyl	R−C(=O)•	?	-oyl	Acetyl

References

↑ Compendium of Chemical Terminology (IUPAC "Gold Book") http://goldbook.iupac.org/F02555.html
↑ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
↑ Brown, Theodore (2002). Chemistry : the central science. Upper Saddle River, NJ: Prentice Hall. p. 1001. ISBN 0130669970.
↑ Moss, G. P.; W.H. Powell. "RC-81.1.1. Monovalent radical centers in saturated acyclic and monocyclic hydrocarbons, and the mononuclear EH4 parent hydrides of the carbon family". IUPAC Recommendations 1993. Department of Chemistry, Queen Mary University of London. Archived from the original on 9 February 2015. Retrieved 25 February 2015.
↑ "R-2. 5 Substituent Prefix Names Derived from Parent Hydrides". IUPAC. 1993. section P-56.2.1
↑ "Revised Nomenclature for Radicals, Ions, Radical Ions and Related Species (IUPAC Recommendations 1993: RC-81.3. Multiple radical centers)".

External links

IUPAC Blue Book (organic nomenclature)
"IUPAC ligand abbreviations" (PDF). IUPAC. 2 April 2004. Archived from the original (PDF) on 27 September 2007. Retrieved 25 February 2015.
_chemical_formula_moiety in CIF dictionary
Functional group synthesis from organic-reaction.com

Functional groups

Only carbon,
hydrogen
and oxygen

Hydrocarbons	Allene Alkene (Allyl, Vinyl) Alkyl (Methyl, Ethyl, Propyl, Butyl, Pentyl) Alkyne Benzyl Carbene Cumulene Methylene bridge Methylene group Methine Phenyl

Other	Acetoxy Acetyl Acryloyl Acyl Aldehyde Alkoxy (Methoxy) Benzoyl Carbonyl Carboxyl Dioxirane Epoxide Ester Ether Ethylenedioxy Hydroxy Ketone Methylenedioxy Peroxide (Organic)

Only one
element
apart from
C, H, O

Nitrogen	Amine Azo compound Cyanate Hydrazone Imide Imine Isocyanate Isonitrile Nitrene Nitrile Nitro compound Nitroso compound Organic amide Oxime

Phosphorus	Phosphonate Phosphonous

Sulfur	Disulfide Sulfone Sulfonic acid Sulfoxide Thial Thioester Thioether Thioketone Thiol

Selenium	Selenol Selenonic acid

Tellurium	Tellurol

Other

See also chemical classification, chemical nomenclature (inorganic, organic)

Concepts in organic chemistry

Aromaticity Covalent bonding Functional groups Nomenclature Organic compounds Organic reactions Organic synthesis Publications Spectroscopy Stereochemistry List of organic compounds

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