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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.

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. 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 is 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.

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).


Table of common functional groupsEdit

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.


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  
Alkene Alkenyl R2C=CR2   alkenyl- -ene  
Alkyne Alkynyl RC≡CR'   alkynyl- -yne  
Benzene derivative Phenyl RC6H5
  phenyl- -benzene  

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 halogenEdit

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  
(Ethyl chloride)
fluoroalkane fluoro RF   fluoro- alkyl fluoride  
(Methyl fluoride)
chloroalkane chloro RCl   chloro- alkyl chloride  
(Methyl chloride)
bromoalkane bromo RBr   bromo- alkyl bromide  
(Methyl bromide)
iodoalkane iodo RI   iodo- alkyl iodide  
(Methyl iodide)

Groups containing oxygenEdit

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   hydroxy- -ol  
Ketone Carbonyl RCOR'   -oyl- (-COR')
oxo- (=O)
(Methyl ethyl ketone)
Aldehyde Aldehyde RCHO   formyl- (-COH)
oxo- (=O)
Acyl halide Haloformyl RCOX   carbonofluoridoyl-
-oyl halide  
Acetyl chloride
(Ethanoyl chloride)
Carbonate Carbonate ester ROCOOR'   (alkoxycarbonyl)oxy- alkyl carbonate  
(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-
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
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  
Orthocarbonate ester Orthocarbonate ester C(OR)(OR')(ORʺ)(OR″) tetralkoxy- tetraalkyl orthocarbonate

Groups containing nitrogenEdit

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-
Amines Primary amine RNH2   amino- -amine  
Secondary amine R2NH   amino- -amine  
Tertiary amine R3N   amino- -amine  
4° ammonium ion R4N+   ammonio- -ammonium  
Imine Primary ketimine RC(=NH)R'   imino- -imine
Secondary ketimine     imino- -imine
Primary aldimine RC(=NH)H   imino- -imine  
Secondary aldimine RC(=NR')H   imino- -imine
Imide Imide (RCO)2NR'   imido- -imide  
Azide Azide RN3   azido- alkyl azide  
Phenyl azide
Azo compound Azo
RN2R'   azo- -diazene  
Methyl orange
(p-dimethylamino-azobenzenesulfonic acid)
Cyanates Cyanate ROCN   cyanato- alkyl cyanate  
Methyl cyanate
Isocyanate RNCO   isocyanato- alkyl isocyanate  
Methyl isocyanate
Nitrate Nitrate RONO2   nitrooxy-, nitroxy-

alkyl nitrate

Amyl nitrate
Nitrile Nitrile RCN   cyano- alkanenitrile
alkyl cyanide
(Phenyl cyanide)
Isonitrile RNC   isocyano- alkaneisonitrile
alkyl isocyanide
Methyl isocyanide
Nitrite Nitrosooxy RONO   nitrosooxy-

alkyl nitrite

Isoamyl nitrite
Nitro compound Nitro RNO2   nitro-    
Nitroso compound Nitroso RNO   nitroso- (Nitrosyl-)    
Oxime Oxime RCH=NOH     Oxime  
Acetone oxime
(2-Propanone oxime)
Pyridine derivative Pyridyl RC5H4N






Groups containing sulfurEdit

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   sulfanyl-
Sulfide RSR'   substituent sulfanyl-

(Methylsulfanyl)methane (prefix) or
Dimethyl sulfide (suffix)
Disulfide Disulfide RSSR'   substituent disulfanyl-

(Methyldisulfanyl)methane (prefix) or
Dimethyl disulfide (suffix)
Sulfoxide Sulfinyl RSOR'   -sulfinyl-
(Methanesulfinyl)methane (prefix) or
Dimethyl sulfoxide (suffix)
Sulfone Sulfonyl RSO2R'   -sulfonyl-
(Methanesulfonyl)methane (prefix) or
Dimethyl sulfone (suffix)
Sulfinic acid Sulfino RSO2H   sulfino-
-sulfinic acid  
2-Aminoethanesulfinic acid
Sulfonic acid Sulfo RSO3H   sulfo-
-sulfonic acid  
Benzenesulfonic acid
Thiocyanate Thiocyanate RSCN   thiocyanato-
substituent thiocyanate  
Phenyl thiocyanate
Isothiocyanate RNCS   isothiocyanato-
substituent isothiocyanate  
Allyl isothiocyanate
Thioketone Carbonothioyl RCSR'   -thioyl-
Thial Carbonothioyl RCSH   methanethioyl-
carbodithioic acid

Groups containing phosphorusEdit

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
Phosphino R3P   phosphanyl- -phosphane  
Phosphonic acid Phosphono     phosphono- substituent phosphonic acid  
Benzylphosphonic acid
Phosphate Phosphate     phosphonooxy-
O-phosphono- (phospho-)
substituent phosphate  
Glyceraldehyde 3-phosphate (suffix)
O-Phosphonocholine (prefix)
Phosphodiester Phosphate HOPO(OR)2   [(alkoxy)hydroxyphosphoryl]oxy-
di(substituent) hydrogen phosphate
phosphoric acid di(substituentester
O‑[(2‑Guanidinoethoxy)hydroxyphosphoryl]‑l‑serine (prefix)

Groups containing boronEdit

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   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 moietiesEdit

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

See alsoEdit


  1. ^ Compendium of Chemical Terminology (IUPAC "Gold Book")
  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)". 

External linksEdit