Functional group

File:Benzyl acetate - functional groups and moieties.svg

Example functional groups of benzyl acetate: Template:Legend-line Template:Legend-line Template:Legend-line

In organic chemistry, a functional group is a substituent or moiety in a molecule that causes the molecule's characteristic chemical reactions. The same functional group will undergo the same or similar chemical reactions regardless of the rest of the molecule's composition. This enables systematic prediction of chemical reactions and behavior of chemical compounds and the design of chemical synthesis. The reactivity of a functional group can be modified by other functional groups nearby. Functional group interconversion can be used in retrosynthetic analysis to plan organic synthesis.

A functional group is a group of atoms in a molecule with distinctive chemical properties, regardless of the other atoms in the molecule. The atoms in a functional group are linked to each other and to the rest of the molecule by covalent bonds. For repeating units of polymers, functional groups attach to their nonpolar core of carbon atoms and thus add chemical character to carbon chains. Functional groups can also be charged, e.g. in carboxylate salts (Template:Chem2), which turns the molecule into a polyatomic ion or a complex ion. Functional groups binding to a central atom in a coordination complex are called ligands. Complexation and solvation are also caused by specific interactions of functional groups. In the common rule of thumb "like dissolves like", it is the shared or mutually well-interacting functional groups which give rise to solubility. For example, sugar dissolves in water because both share the hydroxyl functional group (Template:Chem2) and hydroxyls interact strongly with each other. Plus, when functional groups are more electronegative than atoms they attach to, the functional groups will become polar, and the otherwise nonpolar molecules containing these functional groups become polar and so become soluble in some aqueous environment.

Combining the names of functional groups with the names of the parent alkanes generates what is termed a systematic nomenclature for naming organic compounds. In traditional nomenclature, 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-aminobutyric acid is on the third carbon of the carbon chain attached to the carboxylic acid group. IUPAC conventions call for numeric labeling of the position, e.g. 4-aminobutanoic acid. In traditional names various qualifiers are used to label isomers, for example, isopropanol (IUPAC name: propan-2-ol) is an isomer of n-propanol (propan-1-ol). The term moiety has some overlap with the term "functional group". However, a moiety is an entire "half" of a molecule, which can be not only a single functional group, but also a larger unit consisting of multiple functional groups. For example, an "aryl moiety" may be any group containing an aromatic ring, regardless of how many functional groups the said aryl has.

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

Hydrocarbons are a class of molecule that is defined by functional groups called hydrocarbyls 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 Formula	Prefix	Suffix	Example
Alkane	Alkyl	R(CH2)nH	Alkyl	alkyl-	-ane	Error creating thumbnail: Ethane
Alkene	Alkenyl	R2C=CR2	Alkene	alkenyl-	-ene	Ethylene (Ethene)
Alkyne	Alkynyl	RC≡CR'	$\mathrm{R}-\mathrm{C}\equiv \mathrm{C}-\mathrm{R}{\phantom{A}}^{\prime }$	alkynyl-	-yne	$\mathrm{H}-\mathrm{C}\equiv \mathrm{C}-\mathrm{H}$ Acetylene (Ethyne)
Benzene derivative	Phenyl	RC6H5 RPh	Error creating thumbnail:	phenyl-	-benzene	File:Cumene-skeletal.svg Cumene (Isopropylbenzene)

There are also a large number of branched or ring alkanes that have specific names, e.g., tert-butyl, bornyl, cyclohexyl, etc. There are several functional groups that contain an alkene such as vinyl group, allyl group, or acrylic group. 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 halogen

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	$\mathrm{R}-\mathrm{X}$	halo-	alkyl halide	File:Chloroethane-skeletal.svg Chloroethane (Ethyl chloride)
fluoroalkane	fluoro	RF	$\mathrm{R}-\mathrm{F}$	fluoro-	alkyl fluoride	File:Fluoromethane.svg Fluoromethane (Methyl fluoride)
chloroalkane	chloro	RCl	$\mathrm{R}-\mathrm{C}\mathrm{l}$	chloro-	alkyl chloride	Chloromethane Chloromethane (Methyl chloride)
bromoalkane	bromo	RBr	$\mathrm{R}-\mathrm{B}\mathrm{r}$	bromo-	alkyl bromide	File:Methyl bromide.svg Bromomethane (Methyl bromide)
iodoalkane	iodo	RI	$\mathrm{R}-\mathrm{I}$	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	Structural formula	Prefix	Suffix	Example
Alcohol	Hydroxyl	ROH	Hydroxyl Hydroxyl	hydroxy-	-ol	Methanol
Ketone	Ketone	RCOR'	Ketone	-oyl- (-COR') or oxo- (=O)	-one	Butanone Butanone (Methyl ethyl ketone)
Aldehyde	Aldehyde	RCHO	Error creating thumbnail:	formyl- (-COH) or oxo- (=O)	-al	Error creating thumbnail: Acetaldehyde (Ethanal)
Acyl halide	Haloformyl	RCOX	Acyl halide	carbonofluoridoyl- carbonochloridoyl- carbonobromidoyl- carbonoiodidoyl-	-oyl fluoride -oyl chloride -oyl bromide -oyl iodide	Error creating thumbnail: Acetyl chloride (Ethanoyl chloride)
Carbonate	Carbonate ester	ROCOOR'	Carbonate	(alkoxycarbonyl)oxy-	alkyl carbonate	triphosgene Triphosgene (bis(trichloromethyl) carbonate)
Carboxylate	Carboxylate	RCOO−	Carboxylate Carboxylate	carboxylato-	-oate	Sodium acetate Sodium acetate (Sodium ethanoate)
Carboxylic acid	Carboxyl	RCOOH	Carboxylic acid	carboxy-	-oic acid	Acetic acid Acetic acid (Ethanoic acid)
Ester	Carboalkoxy	RCOOR'	Error creating thumbnail:	alkanoyloxy- or alkoxycarbonyl	alkyl alkanoate	Error creating thumbnail: Ethyl butyrate (Ethyl butanoate)
Hydroperoxide	Hydroperoxy	ROOH	Error creating thumbnail:	hydroperoxy-	alkyl hydroperoxide	tert-Butyl hydroperoxide
Peroxide	Peroxy	ROOR'	Peroxy	peroxy-	alkyl peroxide	Di-tert-butyl peroxide Di-tert-butyl peroxide
Ether	Ether	ROR'	Ether Ether	alkoxy-	alkyl ether	Diethyl ether (Ethoxyethane)
Hemiacetal	Hemiacetal	R2CH(OR1)(OH)	Error creating thumbnail:	alkoxy -ol	-al alkyl hemiacetal
Hemiketal	Hemiketal	RC(ORʺ)(OH)R'	Hemiketal	alkoxy -ol	-one alkyl hemiketal
Acetal	Acetal	RCH(OR')(OR")	Acetal	dialkoxy-	-al dialkyl acetal
Ketal (or Acetal)	Ketal (or Acetal)	Template:Nowrap	Ketal	dialkoxy-	-one dialkyl ketal
Orthoester	Orthoester	Template:Nowrap	Orthoester	trialkoxy-
Heterocycle (if cyclic)	Methylenedioxy	Template:Nowrap	File:Methylenedioxy graphic (ChemDraw).png	methylenedioxy-	-dioxole	File:Benzo(d)(1,3)dioxole 200.svg 1,2-Methylenedioxybenzene (1,3-Benzodioxole)
Orthocarbonate ester	Orthocarbonate ester	Template:Nowrap	Error creating thumbnail:	tetralkoxy-	tetraalkyl orthocarbonate	File:Tetramethylorthocarbonat.svg Tetramethoxymethane
Organic acid anhydride	Carboxylic anhydride	Template:Nowrap	Carboxylic anhydride		anhydride	Error creating thumbnail: Butyric anhydride

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	RCONR'R"	Amide	carboxamido- or carbamoyl-	-amide	acetamide Acetamide (Ethanamide)
Amidine	Amidine	R4C(NR1)(NR2R3)	File:Amidines.svg	amidino-	-amidine	File:Acetamidine-2D-skeletal.pngacetamidine (acetimidamide)
Guanidine	Guanidine	RNC(NR2)2)	File:Guanidine-group-2D-skeletal.svg	Guanidin-	-Guanidine	File:Guanidinopropionic acid.pngGuanidinopropionic acid
Amines	Primary amine	RNH2	Primary amine	amino-	-amine	Error creating thumbnail: Methylamine (Methanamine)
	Secondary amine	R'R"NH	Secondary amine	amino-	-amine	dimethylamine Dimethylamine
	Tertiary amine	R3N	Tertiary amine	amino-	-amine	Error creating thumbnail: Trimethylamine
	4° ammonium ion	R4N+	Error creating thumbnail:	ammonio-	-ammonium	Error creating thumbnail: Choline
	Hydrazone	R'R"CN2H2		hydrazino-	-hydrazine	Error creating thumbnail: Benzophenone
Imine	Primary ketimine	RC(=NH)R'	Imine	imino-	-imine
	Secondary ketimine	$\mathrm{R}\mathrm{C}(=\mathrm{N}\mathrm{R}{\phantom{A}}^{\prime \prime })\mathrm{R}{\phantom{A}}^{\prime }$	Imine	imino-	-imine
	Primary aldimine	RC(=NH)H	Imine	imino-	-imine	Error creating thumbnail: Ethanimine
	Secondary aldimine	RC(=NR')H		imino-	-imine
Imide	Imide	(RCO)2NR'	Imide	imido-	-imide	Error creating thumbnail: Succinimide (Pyrrolidine-2,5-dione)
Azide	Azide	RN3		azido-	alkyl azide	Phenyl azide Phenyl azide (Azidobenzene)
Azo compound	Azo (Diimide)	RN2R'	Error creating thumbnail:	azo-	-diazene	Methyl orange Methyl orange (p-dimethylamino-azobenzenesulfonic acid)
Cyanates	Cyanate	ROCN	Cyanate	cyanato-	alkyl cyanate	Methyl cyanate Methyl cyanate
	Isocyanate	RNCO		isocyanato-	alkyl isocyanate	Error creating thumbnail: Methyl isocyanate
Nitrate	Nitrate	RONO2	Nitrate	nitrooxy-, nitroxy-	alkyl nitrate	Amyl nitrate (1-nitrooxypentane)
Nitrile	Nitrile	RCN	$\mathrm{R}-\equiv \mathrm{N}$	cyano-	alkanenitrile alkyl cyanide	Benzonitrile Benzonitrile (Phenyl cyanide)
	Isonitrile	RNC	File:Isonitrile structural formula.svg	isocyano-	alkaneisonitrile alkyl isocyanide	$\mathrm{H}{\phantom{A}}_3\mathrm{C}-\stackrel{+}{\mathrm{N}}\equiv \mathrm{C}{\phantom{A}}^{-}$ Methyl isocyanide
Nitrite	Nitrosooxy	RONO	Nitrite	nitrosooxy-	alkyl nitrite	Amyl nitrite Isoamyl nitrite (3-methyl-1-nitrosooxybutane)
Nitro compound	Nitro	RNO2	Error creating thumbnail:	nitro-		Nitromethane Nitromethane
Nitroso compound	Nitroso	RNO	Nitroso	nitroso- (Nitrosyl-)		Nitrosobenzene Nitrosobenzene
Oxime	Oxime	RCH=NOH			Oxime	Acetone oxime (2-Propanone oxime)
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
Carbamate ester	Carbamate	RO(C=O)NR2	Error creating thumbnail:	(-carbamoyl)oxy-	-carbamate	Chlorpropham Chlorpropham (Isopropyl (3-chlorophenyl)carbamate)

Groups containing sulfur

Compounds that contain sulfur exhibit unique chemistry due to sulfur's ability to form more bonds than oxygen, its 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	Structural formula	Prefix	Suffix	Example
Thiol	Sulfhydryl	RSH	Error creating thumbnail:	sulfanyl- (-SH)	-thiol	Ethanethiol Ethanethiol
Sulfide (Thioether)	Sulfide	RSR'	Sulfide group	substituent sulfanyl- (-SR')	di(substituent) sulfide	(Methylsulfanyl)methane (prefix) or Dimethyl sulfide (suffix)
Disulfide	Disulfide	RSSR'		substituent disulfanyl- (-SSR')	di(substituent) disulfide	Dimethyl disulfide (Methyldisulfanyl)methane (prefix) or Dimethyl disulfide (suffix)
Sulfoxide	Sulfinyl	RSOR'	Error creating thumbnail:	-sulfinyl- (-SOR')	di(substituent) sulfoxide	DMSO (Methanesulfinyl)methane (prefix) or Dimethyl sulfoxide (suffix)
Sulfone	Sulfonyl	RSO2R'	Error creating thumbnail:	-sulfonyl- (-SO2R')	di(substituent) sulfone	Dimethyl sulfone (Methanesulfonyl)methane (prefix) or Dimethyl sulfone (suffix)
Sulfinic acid	Sulfino	RSO2H	Error creating thumbnail:	sulfino- (-SO2H)	-sulfinic acid	2-Aminoethanesulfinic acid
Sulfonic acid	Sulfo	RSO3H	Sulfonyl group	sulfo- (-SO3H)	-sulfonic acid	Benzenesulfonic acid
Sulfonate ester	Sulfo	RSO3R'	Error creating thumbnail:	(-sulfonyl)oxy- or alkoxysulfonyl-	R' R-sulfonate	Methyl trifluoromethanesulfonate Methyl trifluoromethanesulfonate or Methoxysulfonyl trifluoromethane (prefix)
Thiocyanate	Thiocyanate	RSCN		thiocyanato- (-SCN)	substituent thiocyanate	Phenyl thiocyanate
	Isothiocyanate	RNCS	Isothiocyanate	isothiocyanato- (-NCS)	substituent isothiocyanate	Allyl isothiocyanate Allyl isothiocyanate
Thioketone	Carbonothioyl	RCSR'	Thione	-thioyl- (-CSR') or sulfanylidene- (=S)	-thione	Diphenylmethanethione (Thiobenzophenone)
Thial	Carbonothioyl	RCSH	Thial	methanethioyl- (-CSH) or sulfanylidene- (=S)	-thial
Thiocarboxylic acid	Carbothioic S-acid	RC=OSH	Error creating thumbnail: Thioic S-acid	mercaptocarbonyl-	-thioic S-acid	Error creating thumbnail: Thiobenzoic acid (benzothioic S-acid)
	Carbothioic O-acid	RC=SOH	Thioic O-acid	hydroxy(thiocarbonyl)-	-thioic O-acid
Thioester	Thiolester	RC=OSR'	Thiolester		S-alkyl-alkane-thioate	S-methyl thioacrylate S-methyl thioacrylate (S-methyl prop-2-enethioate)
	Thionoester	RC=SOR'	Thionoester		O-alkyl-alkane-thioate
Dithiocarboxylic acid	Carbodithioic acid	RCS2H	Dithiocarboxylic acid	dithiocarboxy-	-dithioic acid	Dithiobenzoic acid Dithiobenzoic acid (Benzenecarbodithioic acid)
Dithiocarboxylic acid ester	Carbodithio	RC=SSR'	Dithioate		-dithioate

Groups containing phosphorus

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

Chemical class	Group	Formula	Structural formula	Prefix	Suffix	Example
Phosphine (Phosphane)	Phosphino	R3P	Error creating thumbnail:	phosphanyl-	-phosphane	Error creating thumbnail: Methylpropylphosphane
Phosphonic acid	Phosphono	$\mathrm{R}\mathrm{P}(=\mathrm{O})(\mathrm{O}\mathrm{H}){\phantom{A}}_2$	Phosphono group	phosphono-	substituent phosphonic acid	Benzylphosphonic acid Benzylphosphonic acid
Phosphate	Phosphate	$\mathrm{R}\mathrm{O}\mathrm{P}(=\mathrm{O})(\mathrm{O}\mathrm{H}){\phantom{A}}_2$	Phosphate group	phosphonooxy- or O-phosphono- (phospho-)	substituent phosphate	Glyceraldehyde 3-phosphate Glyceraldehyde 3-phosphate (suffix)
						O-Phosphonocholine (prefix) (Phosphocholine)
Phosphodiester	Phosphate	HOPO(OR)2	Error creating thumbnail:	[(alkoxy)hydroxyphosphoryl]oxy- or O-[(alkoxy)hydroxyphosphoryl]-	di(substituent) hydrogen phosphate or phosphoric acid di(substituent) ester	DNA
						O‑[(2‑Guanidinoethoxy)hydroxyphosphoryl]‑Template:Smallcaps‑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	Structural formula	Prefix	Suffix	Example
Boronic acid	Borono	RB(OH)2	Error creating thumbnail:	Borono-	substituent boronic acid	Template:Center
Boronic ester	Boronate	RB(OR)2	File:Boronate-ester-2D.svg	O-[bis(alkoxy)alkylboronyl]-	substituent boronic acid di(substituent) ester
Borinic acid	Borino	R2BOH	File:Borinic-acid-2D.svg	Hydroxyborino-	di(substituent) borinic acid
Borinic ester	Borinate	R2BOR	Error creating thumbnail:	O-[alkoxydialkylboronyl]-	di(substituent) borinic acid substituent ester	Template:Center

Groups containing metals

Chemical class	Structural formula	Prefix	Suffix	Example
Alkyllithium	RLi	(tri/di)alkyl-	-lithium	File:Meli is.svg methyllithium
Alkylmagnesium halide	RMgX (X=Cl, Br, I)Template:Ref label		-magnesium halide	methylmagnesium chloride
Alkylaluminium	Al2R6		-aluminium	File:Trimethylaluminium-from-xtal-3D-bs-17.png trimethylaluminium
Silyl ether	R3SiOR		-silyl ether	trimethylsilyl triflate

Template:Note label Fluorine is too electronegative to be bonded to magnesium; it becomes an ionic salt instead.

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").

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 methylidene 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 double 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), carbyne for methylidyne, and trityl for triphenylmethyl.

Chemical class	Group	Formula	Structural formula	Prefix	Suffix	Example
Single bond		R•		Ylo-	-yl	Template:Center
Double bond		R:		?	-ylidene	Template:Center
Triple bond		R⫶		?	-ylidyne	Template:Center
Carboxylic acyl radical	Acyl	R−C(=O)•		?	-oyl	Template:Center

See also

• Category:Functional groups
• Group contribution method

External links

• IUPAC Blue Book (organic nomenclature)
• Template:Cite web
• Functional group video