Functional Groups in Organic Chemistry

Functional groups are parts of molecules responsible for characteristic reactions.
Functional groups are parts of molecules responsible for characteristic reactions. LAGUNA DESIGN / Getty Images

Functional groups are groups of atoms found within molecules that are involved in the chemical reactions characteristic of those molecules. Functional groups can pertain to any molecules, but you will usually hear about them in the context of organic chemistry. The symbol R and R' refer to an attached hydrogen or hydrocarbon side chain or sometimes to any group of atoms.

This is an alphabetical list of important functional groups:

Acyl Group

Acyl Group Chemical Structure
Functional Groups The acyl functional group is the part of the structure highlighted in green. Todd Helmenstine

An acyl group is a functional group with formula RCO- where R is bound to the carbon atom with a single bond.

Acyl Halide Functional Group

Acyl Halide Functional Group
Functional Groups This is the general structure of an aycl halide functional group where X is a halogen atom. Todd Helmenstine

An acyl halide is a functional group with formula R-COX where X is a halogen atom.

Aldehyde Functional Group

The aldehyde functional group has the formula RCHO.
The aldehyde functional group has the formula RCHO. It has the prefix aldo- and the suffix -al. Ben Mills

Alkenyl Functional Group

The alkenyl functional group is a type of hydrocarbon functional group based on an alkene.
The alkenyl functional group is a type of hydrocarbon functional group based on an alkene. It is characterized by its double bond. Ben Mills

Alkyl Functional Group

The isopropyl group is an example of an alkyl group.
The isopropyl group is an example of an alkyl group.  Su-no-G

Alkynyl Functional Group

The alkynyl functional group is a hydrocarbon functional group based on an alkyne.
The alkynyl functional group is a hydrocarbon functional group based on an alkyne. It is characterized by its triple bond. Ben Mills

Azide Functional Group

The formula for the azide functional group is RN3.

Azo or Diimide Functional Group

This is the structure of the azo or diimide functional group.
This is the structure of the azo or diimide functional group. Ben Mills

The formula for the azo or diimide functional group is RN2R'.

Benzyl Functional Group

The benzyl functional group is a hydrocarbon functional group derived from toluene.
The benzyl functional group is a hydrocarbon functional group derived from toluene. Ben Mills

Bromo Functional Group

The bromo functional group is a bromoalkane characterized by a carbon-bromine bond.
The bromo functional group is a bromoalkane characterized by a carbon-bromine bond. Ben Mills

Butyl Functional Group

This is the chemical structure of the butyl functional group.
This is the chemical structure of the butyl functional group. Todd Helmenstine

The molecular formula for the butyl functional group is R-C4H9.

Carbonate Functional Group

The carbonate ester functional group has the formula ROCOOR and derived from carbonate.
The carbonate ester functional group has the formula ROCOOR and derived from carbonate. Ben Mills

Carbonyl Functional Group

The carbonyl functional group is based on the ketone group. It has the formula RCOR'.
The carbonyl functional group is based on the ketone group. It has the formula RCOR'. The prefix for this group is keto- or oxo- or its suffix is -one. Ben Mills

Carboxamide Functional Group

The carboxamide functional group is an amide.
The carboxamide functional group is an amide. Ben Mills

The formula for a carboxamide group is RCONR2.

Carboxyl Functional Group

Vinyl acetate contains the carboxyl group.
Vinyl acetate contains the carboxyl group. Bacsica / Getty Images

 The formula for the carboxyl functional group is RCOOH. It is based on carboxylic acid.

Carboxylate Functional Group

The formula for the carboxylate functional group is RCOO−.
The formula for the carboxylate functional group is RCOO−. The carboxylate group is based on carboxylate and has the carboxy- prefix or -oate suffix. Ben Mills

Chloro Functional Group

The chloro functional group is a chloroalkane. It is characterized by a carbon-chlorine bond.
The chloro functional group is a chloroalkane. It is characterized by a carbon-chlorine bond. Ben Mills

Cyanate Functional Group

The formula of the cyanate functional group is ROCN.
The formula of the cyanate functional group is ROCN. Ben Mills

Disulfide Functional Group

The formula for the disulfide functional group is RSSR'.
The formula for the disulfide functional group is RSSR'. InfoCan, Wikipedia Commons
The formula for the ester functional group is RCOOR'.
The formula for the ester functional group is RCOOR'. Ben Mills

Ether Functional Group

The general formula for the ether functional group is ROR'.
The general formula for the ether functional group is ROR'. Ben Mills

Ethyl Functional Group

This is the chemical structure of the ethyl functional group.
Functional Groups This is the chemical structure of the ethyl functional group. Todd Helmenstine

The molecular formula for the ethyl functional group is C2H5.

Fluoro Functional Group

The fluoro functional group is a fluoroalkane. It contains a carbon-fluorine bond.
The fluoro functional group is a fluoroalkane. It contains a carbon-fluorine bond. Ben Mills

Halo Functional Group

The halo functional group contains a carbon-halogen bond.
The halo functional group refers to any haloalkane, or alkane containing an atom of a halogen, such as chlorine, bromine, or fluorine. The halo functional group contains a carbon-halogen bond. Ben Mills

Haloformyl Functional Group

The haloformyl functional group is an acyl halide.
The haloformyl functional group is an acyl halide characterized by a carbon-oxygen double bond and a carbon-halogen bond. Ben Mills

Heptyl Functional Group

This is the chemical structure of the heptyl functional group.
This is the chemical structure of the heptyl functional group. Todd Helmenstine

The molecular formula for the heptyl functional group is R-C7H15.

Hexyl Functional Group

This is the chemical structure of the hexyl functional group.
This is the chemical structure of the hexyl functional group. Todd Helmenstine

The molecular formula for the hexyl functional group is R-C6H13.

Hydrazone Functional Group

This is the general structure of the hydrazone functional group.
Functional Groups This is the general structure of the hydrazone functional group. Todd Helmenstine

The hydrazone functional group has the formula R1R2C=NNH2.

Hydroperoxy Functional Group

 The formula for the hydroperoxy functional group is ROOH. It is based on hydroperoxide.

Hydroxyl Functional Group

The hydroxyl functional group is an oxygen-containing group based on an alcohol or OH group.
The hydroxyl functional group is an oxygen-containing group based on an alcohol or OH group. Ben Mills

Imide Functional Group

The formula for the imide functional group is RC(=O)NC(=O)R'.
The formula for the imide functional group is RC(=O)NC(=O)R'. InfoCan, Wikipedia Commons

Iodo Functional Group

The iodo functional group is an iodoalkane with a carbon-iodine bond.
The iodo functional group is an iodoalkane with a carbon-iodine bond. Ben Mills

Isocyanate Functional Group

The formula for the isocyanate functional group is RNCO.
The formula for the isocyanate functional group is RNCO. Ben Mills

Isothiocyanate Group

The formula for the isothiocyanate group is RNCS.
The formula for the isothiocyanate group is RNCS. Ben Mills

Ketone Functional Group

This is the general structure of the ketone functional group.
This is the general structure of the ketone functional group. Todd Helmenstine

Ketone is a carbonyl group bonded to two carbon atoms where neither R1 nor R2 can be hydrogen atoms.

Methoxy Functional Group

This is the general chemical structure of the methoxy functional group.
Functional Groups This is the general chemical structure of the methoxy functional group. Todd Helmenstine

The methoxy group is the simplest alkoxy group. The methoxy group is commonly abbreviated -OMe in reactions.

Methyl Functional Group

This is the chemical structure of the methyl functional group.
This is the chemical structure of the methyl functional group. Todd Helmenstine

The molecular formula for the methyl functional group is R-CH3

Nitrate Functional Group

Nitric acid is the basis for the nitrate group.
Nitric acid is the basis for the nitrate group. MOLEKUUL/SCIENCE PHOTO LIBRARY / Getty Images

The general formula for a nitrate is RONO2.

Nitrile Functional Group

The formula for the nitrile functional group is RCN.
The formula for the nitrile functional group is RCN. Ben Mills

Nitro Functional Group

This is the two-dimensional structure of the nitro functional group.
This is the two-dimensional structure of the nitro functional group. Ben Mills

The formula of the nitro functional group is RNO2.

Nonyl Functional Group

This is the chemical structure of the nonyl functional group.
This is the chemical structure of the nonyl functional group. Todd Helmenstine

The molecular formula for the nonyl functional group is R-C9H19.

Octyl Functional Group

This is the chemical structure of the octyl functional group.
This is the chemical structure of the octyl functional group. Todd Helmenstine

The molecular formula for the octyl functional group is R-C8H17.

Pentyl Functional Group

This is the chemical structure of the pentyl functional group.
This is the chemical structure of the pentyl functional group. Todd Helmenstine

The molecular formula for pentyl functional group is R-C5H11.

Peroxy Functional Group

The formula for the peroxy functional group is ROOR. The peroxy group is based on peroxide.
The formula for the peroxy functional group is ROOR. The peroxy group is based on peroxide. Ben Mills

Phenyl Functional Group

The phenyl functional group is a hydrocarbon functional group derived from benzene.
The phenyl functional group is a hydrocarbon functional group derived from benzene. Ben Mills

Phosphate Functional Group

This is the two-dimensional structure of the phosphate functional group.
This is the two-dimensional structure of the phosphate functional group. Ben Mills

The formula for the phosphate functional group is ROP(=O)(OH)2.

Phosphine or Phosphino Functional Group

The formula for a phosphine is R3P.

Phosphodiester Group

The phosphodiester group is a type of phosphate.
The phosphodiester group is a type of phosphate. Ben Mills

The formula for the phosphodiester group is HOPO(OR)2.

Phosphonic Acid Group

This is the two-dimensional structure of the phosphonic acid or phosphono functional group.
This is the two-dimensional structure of the phosphonic acid or phosphono functional group. Ben Mills

The formula for the phosphonic acid functional group is RP(=O)(OH)2.

Primary Amine Group

A primary amine is one of the amine functional groups.
A primary amine is one of the amine functional groups. Ben Mills

The formula for a primary amine is RNH2.

Primary Ketimine Group

The formula of the primary ketimine group is RC(=NH)R'. This is a type of primary imine.
The formula of the primary ketimine group is RC(=NH)R'. This is a type of primary imine. Ben Mills

Propyl Functional Group

This is the chemical structure of the propyl functional group.
This is the chemical structure of the propyl functional group. Todd Helmenstine

The molecular formula for the propyl functional group is R-C3H7.

Pyridyl Functional Group

The pyridyl functional group is a derivative of pyridine.
The pyridyl functional group is a derivative of pyridine. Ben Mills

The formula for the pyridyl group is RC5H4N. The location of the nitrogen in the ring varies.

Secondary Aldimine Group

The secondary aldimine functional group has the formula RC(=NR')H. It is a type of imine.
The secondary aldimine functional group has the formula RC(=NR')H. It is a type of imine. Ben Mills

Secondary Amine Group

A secondary amine group is a type of amine.
A secondary amine group is a type of amine. Ben Mills

The formula for a secondary amine is R2NH.

Secondary Ketimine Group

The formula of the secondary ketimine functional group is RC(=NR)R'.
The formula of the secondary ketimine functional group is RC(=NR)R'. The secondary ketimine is a type of secondary imine. Ben Mills

Sulfide Group

 The formula for the sulfide or thioether functional group is RSR'.

Sulfone Functional Group

This is the two-dimensional structure of the sulfone or sulfonyl functional group.
This is the two-dimensional structure of the sulfone or sulfonyl functional group. Ben Mills

The formula for the sulfone functional group is RSO2R'.

Sulfonic Acid Functional Group

This is the two-dimensional structure of the sulfonic acid or sulfo functional group.
This is the two-dimensional structure of the sulfonic acid or sulfo functional group. Ben Mills

The formula for the sulfonic acid functional group is RSO3H.

Sulfoxide Functional Group

The formula for the sulfoxide or sulfinyl functional group is RSOR'.
The formula for the sulfoxide or sulfinyl functional group is RSOR'. Ben Mills

Tertiary Amine Group

A tertiary amine group is a type of amine.
A tertiary amine group is a type of amine. Ben Mills

The formula for a tertiary amine is R3N.

Thiocyanate Functional Group

The formula of the thiocyanate functional group is RSCN.
The formula of the thiocyanate functional group is RSCN. Ben Mills

Thiol Functional Group

The formula for the thiol or sulfhydryl functional group is RSH.
The formula for the thiol or sulfhydryl functional group is RSH. Ben Mills

Vinyl Functional Group

This is the chemical structure of the vinyl functional group.
Functional Groups This is the chemical structure of the vinyl or ethenyl functional group. Todd Helmenstine

The molecular formula for the vinyl functional group is C2H3. It is also known as the ethenyl functional group.