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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.
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, 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.[1][2] 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 (–COO), 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 (–OH) 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 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.[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

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
Ethan Keilstrich.svg

Ethane
Alkene Alkenyl R2C=CR2
Alkene
alkenyl- -ene
ethylene

Ethylene
(Ethene)
Alkyne Alkynyl RC≡CR' alkynyl- -yne
Acetylene
(Ethyne)
Benzene derivative Phenyl RC6H5
RPh
Phenyl
phenyl- -benzene
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. 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 halo- alkyl halide
Chloroethane-skeletal.svg

Chloroethane
(Ethyl chloride)
fluoroalkane fluoro RF fluoro- alkyl fluoride
Fluoromethane.svg

Fluoromethane
(Methyl fluoride)
chloroalkane chloro RCl chloro- alkyl chloride
Chloromethane

Chloromethane
(Methyl chloride)
bromoalkane bromo RBr bromo- alkyl bromide
Methyl bromide.svg

Bromomethane
(Methyl bromide)
iodoalkane iodo RI iodo- alkyl iodide
Iodomethane

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
hydroxy- -ol
methanol

Methanol
Ketone Carbonyl RCOR'
Ketone
-oyl- (-COR')
or
oxo- (=O)
-one
Butanone

Butanone
(Methyl ethyl ketone)
Aldehyde Aldehyde RCHO
Aldehyde
formyl- (-COH)
or
oxo- (=O)
-al
acetaldehyde

Acetaldehyde
(Ethanal)
Acyl halide Haloformyl RCOX
Acyl halide
carbonofluoridoyl-
carbonochloridoyl-
carbonobromidoyl-
carbonoiodidoyl-
-oyl fluoride
-oyl chloride
-oyl bromide
-oyl iodide
Acetyl chloride

Acetyl chloride
(Ethanoyl chloride)
Carbonate Carbonate ester ROCOOR'
Carbonate
(alkoxycarbonyl)oxy- alkyl carbonate
triphosgene

Triphosgene
(bis(trichloromethyl) 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)
Ester Carboalkoxy RCOOR'
Ester
alkanoyloxy-
or
alkoxycarbonyl
alkyl alkanoate
Ethyl butyrate

Ethyl butyrate
(Ethyl butanoate)
Hydroperoxide Hydroperoxy ROOH
Hydroperoxy
hydroperoxy- alkyl hydroperoxide
tert-Butyl hydroperoxide

tert-Butyl hydroperoxide
Peroxide Peroxy ROOR'
Peroxy
peroxy- alkyl peroxide
Di-tert-butyl peroxide

Di-tert-butyl peroxide
Ether Ether ROR'
Ether
alkoxy- alkyl ether
Diethyl ether

Diethyl ether
(Ethoxyethane)
Hemiacetal Hemiacetal R2CH(OR1)(OH)
Hemiacetal
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) RC(OR")(OR‴)R'
Ketal
dialkoxy- -one dialkyl ketal
Orthoester Orthoester RC(OR')(OR")(OR‴)
Orthoester
trialkoxy-
Heterocycle
(if cyclic)
Methylenedioxy (–OCH2O–)

Methylenedioxy graphic (ChemDraw).png

methylenedioxy- -dioxole
1,3-Benzodioxole.png

1,2-Methylenedioxybenzene
(1,3-Benzodioxole)
Orthocarbonate ester Orthocarbonate ester C(OR)(OR')(OR")(OR‴)
Orthocarbonate ester
tetralkoxy- tetraalkyl orthocarbonate
Tetramethylorthocarbonat.svg

Tetramethoxymethane
Organic acid anhydride Carboxylic anhydride R1(CO)O(CO)R2
Carboxylic anhydride
anhydride
Butyric anhydride

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 RC(NR)NR2
Amidines.svg
amidino- -amidine
acetamidine

(acetimidamide)

Amines Primary amine RNH2
Primary amine
amino- -amine
methylamine

Methylamine
(Methanamine)
Secondary amine R'R"NH
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
Imine
imino- -imine
Primary aldimine RC(=NH)H
Imine
imino- -imine
Ethanimine

Ethanimine
Secondary aldimine RC(=NR')H
Imine
imino- -imine
Imide Imide (RCO)2NR'
Imide
imido- -imide
Succinimide

Succinimide
(Pyrrolidine-2,5-dione)
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
Methyl cyanate

Methyl cyanate
Isocyanate RNCO
Isocyanate
isocyanato- alkyl isocyanate
Methyl isocyanate

Methyl isocyanate
Nitrate Nitrate RONO2
Nitrate
nitrooxy-, nitroxy-

alkyl nitrate

Amyl nitrate

Amyl nitrate
(1-nitrooxypentane)
Nitrile Nitrile RCN cyano- alkanenitrile
alkyl cyanide
Benzonitrile

Benzonitrile
(Phenyl cyanide)
Isonitrile RNC isocyano- alkaneisonitrile
alkyl isocyanide

Methyl isocyanide
Nitrite Nitrosooxy RONO
Nitrite
nitrosooxy-

alkyl nitrite

Amyl nitrite

Isoamyl nitrite
(3-methyl-1-nitrosooxybutane)
Nitro compound Nitro RNO2
Nitro
nitro-  
Nitromethane

Nitromethane
Nitroso compound Nitroso RNO
Nitroso
nitroso- (Nitrosyl-)  
Nitrosobenzene

Nitrosobenzene
Oxime Oxime RCH=NOH
Oxime
  Oxime
Acetone 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
Carbamate
(-carbamoyl)oxy- -carbamate
Chlorpropham

Chlorpropham
(Isopropyl (3-chlorophenyl)carbamate)

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 Structural Formula Prefix Suffix Example
Thiol Sulfhydryl RSH
Sulfhydryl
sulfanyl-
(-SH)
-thiol
Ethanethiol

Ethanethiol
Sulfide
(Thioether)
Sulfide RSR'
Sulfide group
substituent sulfanyl-
(-SR')
di(substituentsulfide
Dimethyl sulfide


(Methylsulfanyl)methane (prefix) or
Dimethyl sulfide (suffix)
Disulfide Disulfide RSSR'
Disulfide
substituent disulfanyl-
(-SSR')
di(substituentdisulfide
Dimethyl disulfide


(Methyldisulfanyl)methane (prefix) or
Dimethyl disulfide (suffix)
Sulfoxide Sulfinyl RSOR'
Sulfinyl group
-sulfinyl-
(-SOR')
di(substituentsulfoxide
DMSO

(Methanesulfinyl)methane (prefix) or
Dimethyl sulfoxide (suffix)
Sulfone Sulfonyl RSO2R'
Sulfonyl group
-sulfonyl-
(-SO2R')
di(substituentsulfone
Dimethyl sulfone

(Methanesulfonyl)methane (prefix) or
Dimethyl sulfone (suffix)
Sulfinic acid Sulfino RSO2H
Sulfinic-acid-2D.svg
sulfino-
(-SO2H)
-sulfinic acid
Hypotaurine

2-Aminoethanesulfinic acid
Sulfonic acid Sulfo RSO3H
Sulfonyl group
sulfo-
(-SO3H)
-sulfonic acid
Benzenesulfonic acid

Benzenesulfonic acid
Sulfonate ester Sulfo RSO3R'
Sulfonic ester
(-sulfonyl)oxy-
or
alkoxysulfonyl-
R' R-sulfonate
Methyl trifluoromethanesulfonate

Methyl trifluoromethanesulfonate or
Methoxysulfonyl trifluoromethane (prefix)
Thiocyanate Thiocyanate RSCN
Thiocyanate
thiocyanato-
(-SCN)
substituent thiocyanate
Phenyl 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

Diphenylmethanethione
(Thiobenzophenone)
Thial Carbonothioyl RCSH
Thial
methanethioyl-
(-CSH)
or
sulfanylidene-
(=S)
-thial
Thiocarboxylic acid Carbothioic S-acid RC=OSH
Thioic S-acid
mercaptocarbonyl- -thioic S-acid
Thiobenzoic acid

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 their ability to form more bonds than nitrogen, their lighter analogues on the periodic table.

Chemical class Group Formula Structural Formula Prefix Suffix Example
Phosphine
(Phosphane)
Phosphino R3P
A tertiary phosphine
phosphanyl- -phosphane
Methylpropylphosphane

Methylpropylphosphane
Phosphonic acid Phosphono
Phosphono group
phosphono- substituent phosphonic acid
Benzylphosphonic acid

Benzylphosphonic acid
Phosphate Phosphate
Phosphate group
phosphonooxy-
or
O-phosphono- (phospho-)
substituent phosphate
Glyceraldehyde 3-phosphate

Glyceraldehyde 3-phosphate (suffix)
Phosphocholine

O-Phosphonocholine (prefix)
(Phosphocholine)
Phosphodiester Phosphate HOPO(OR)2
Phosphodiester
[(alkoxy)hydroxyphosphoryl]oxy-
or
O-[(alkoxy)hydroxyphosphoryl]-
di(substituent) hydrogen phosphate
or
phosphoric acid di(substituentester
DNA
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 Structural Formula Prefix Suffix Example
Boronic acid Borono RB(OH)2
Boronic-acid-2D.svg
Borono- substituent
boronic acid
Phenylboronic acid

Phenylboronic acid
Boronic ester Boronate RB(OR)2
Boronate-ester-2D.svg
O-[bis(alkoxy)alkylboronyl]- substituent
boronic acid
di(substituent) ester
Borinic acid Borino R2BOH
Borinic-acid-2D.svg
Hydroxyborino- di(substituent)
borinic acid
Borinic ester Borinate R2BOR
Borinate-ester-2D.svg
O-[alkoxydialkylboronyl]- di(substituent)
borinic acid
substituent ester
2-Aminoethoxydiphenyl borate

Diphenylborinic acid 2-aminoethyl ester
(2-Aminoethoxydiphenyl borate)

Groups containing metals

Chemical Class Structural Formula Prefix Suffix Example
Alkyllithium RLi (tri/di)alkyl- -lithium
Meli is.svg

methyllithium

Alkylmagnesium halide RMgX (X=Cl, Br, I)[note 1] -magnesium halide
Methylmagnesiumchloride.svg

methylmagnesium chloride

Alkylaluminium Al2R6 -aluminium
Trimethylaluminium-from-xtal-3D-bs-17.png

trimethylaluminium

Silyl ether R3SiOR -silyl ether
Trimethylsilyl triflate.svg

trimethylsilyl triflate

note 1 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").[4]

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 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),[5] carbyne for methylidyne, and trityl for triphenylmethyl.

Chemical class Group Formula Structural 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

See also

References

  1. ^ Compendium of Chemical Terminology (IUPAC "Gold Book") functional group
  2. ^ March, Jerry (1985), Advanced Organic Chemistry: Reactions, Mechanisms, and Structure (3rd ed.), New York: Wiley, ISBN 0-471-85472-7
  3. ^ Brown, Theodore (2002). Chemistry: the central science. Upper Saddle River, NJ: Prentice Hall. p. 1001. ISBN 0130669970.
  4. ^ 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.
  5. ^ "R-2. 5 Substituent Prefix Names Derived from Parent Hydrides". IUPAC. 1993. section P-56.2.1
  6. ^ "Revised Nomenclature for Radicals, Ions, Radical Ions and Related Species (IUPAC Recommendations 1993: RC-81.3. Multiple radical centers)". Archived from the original on 2017-06-11. Retrieved 2014-12-02.