Functional group

For other uses, see Functional group (disambiguation).


Benzyl acetate has an ester functional group (in red), an acetyl moiety (circled with green) and an benzyl alcohol moiety (circled with orange).

In organic chemistry, functional groups are specific groups of atoms 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. However, its relative reactivity can be modified by nearby functional groups.

The word moiety is often used synonymously to “functional group”, but according to the IUPAC definition, a moiety is a half of a molecule including substructures of functional groups. For example, an ester is divided into an alcohol and an acyl moiety, but has an ester functional group. The use of the word “moiety” to mean a functional group in the chemistry sense is actually fairly recent. While it has commonly been used in the archeology field to mean the half of a tribal family, it wasn’t until a chance encounter between Elizabeth Bollwerk, an archeology graduate student, and a drug research scientist that the term made the cross-over.

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

The non-hydrogen atoms of functional groups are always associated with each other and with the rest of the molecule by covalent bonds. When the group of atoms is associated with the rest of the molecule primarily by ionic forces, the group is referred to more properly as a polyatomic ion or complex ion. And all of these are called radicals, by a meaning of the term radical that predates the free radical.

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.

Functional groups are attached to the carbon backbone of organic molecules. They determine the characteristics and chemical reactivity of molecules. Functional groups are far less stable than the carbon backbone and are likely to participate in chemical reactions.

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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

Functional groups that vary based upon the number and order of π bonds impart different chemistry. Each listing below contains C-H bonds, but each one differs in type (and scope) of reactivity.

Chemical class
Group
Formula
Structural Formula
Prefix
Suffix
Example

Alkane
Alkyl
RH

alkyl-
-ane

Ethane

Alkene
Alkenyl
R2C=CR2

alkenyl-
-ene

Ethylene
(Ethene)

Alkyne
Alkynyl
RC≡CR’

alkynyl-
-yne

Acetylene
(Ethyne)

Benzene derivative
Phenyl
RC6H5
RPh

phenyl-
-benzene

Cumene
(2-phenylpropane)

Toluene derivative
Benzyl
RCH2C6H5
RBn

benzyl-
1-(substituent)toluene

Benzyl bromide
(1-Bromotoluene)

There are also a large number of branched or ring alkanes that have specific names, e.g. tert-butyl, bornyl, cyclohexyl, etc.

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

halo-
alkyl halide

Chloroethane
(Ethyl chloride)

fluoroalkane
fluoro
RF

fluoro-
alkyl fluoride

Fluoromethane
(Methyl fluoride)

chloroalkane
chloro
RCl

chloro-
alkyl chloride

Chloromethane
(Methyl chloride)

bromoalkane
bromo
RBr

bromo-
alkyl bromide

Bromomethane
(Methyl bromide)

iodoalkane
iodo
RI

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 sp² hybridized oxygen and the donating effects of sp³ hybridized oxygen.

Chemical class
Group
Formula
Structural Formula
Prefix
Suffix
Example

Acyl halide
Haloformyl
RCOX

haloformyl-
-oyl halide

Acetyl chloride
(Ethanoyl chloride)

Alcohol
Hydroxyl
ROH

hydroxy-
-ol

Methanol

Ketone
Carbonyl
RCOR’

keto-, oxo-
-one

Methyl ethyl ketone
(Butanone)

Aldehyde
Aldehyde
RCHO

aldo-
-al

Acetaldehyde
(Ethanal)

Carbonate
Carbonate ester
ROCOOR

alkyl carbonate

Carboxylate
Carboxylate
RCOO−

carboxy-
-oate

Sodium acetate
(Sodium ethanoate)

Carboxylic acid
Carboxyl
RCOOH

carboxy-
-oic acid

Acetic acid
(Ethanoic acid)

Ether
Ether
ROR’

alkoxy-
alkyl alkyl ether

Diethyl ether
(Ethoxyethane)

Ester
Ester
RCOOR’

alkyl alkanoate

Ethyl butyrate
(Ethyl butanoate)

Hydroperoxide
Hydroperoxy
ROOH

hydroperoxy-
alkyl hydroperoxide

Methyl ethyl ketone peroxide

Peroxide
Peroxy
ROOR

peroxy-
alkyl peroxide

Di-tert-butyl peroxide

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-
-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
RC(=NR)R’

imino-
-imine

Primary aldimine
RC(=NH)H

imino-
-imine

Secondary aldimine
RC(=NR’)H

imino-
-imine

Imide
Imide
RC(=O)NC(=O)R’

imido-
-imide

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

Isocyanide
RNC

isocyano-
alkyl isocyanide

Isocyanates
Isocyanate
RNCO

isocyanato-
alkyl isocyanate

Methyl isocyanate

Isothiocyanate
RNCS

isothiocyanato-
alkyl isothiocyanate

Allyl isothiocyanate

Nitrate
Nitrate
RONO2

nitrooxy-, nitroxy-

alkyl nitrate


Amyl nitrate
(1-nitrooxypentane)

Nitrile
Nitrile
RCN

cyano-

alkanenitrile
alkyl cyanide


Benzonitrile
(Phenyl cyanide)

Nitrite
Nitrosooxy
RONO

nitrosooxy-

alkyl nitrite


Isoamyl nitrite
(3-methyl-1-nitrosooxybutane)

Nitro compound
Nitro
RNO2

nitro-
 

Nitromethane

Nitroso compound
Nitroso
RNO

nitroso-
 

Nitrosobenzene

Pyridine derivative
Pyridyl
RC5H4N



4-pyridyl
(pyridin-4-yl)

3-pyridyl
(pyridin-3-yl)

2-pyridyl
(pyridin-2-yl)

-pyridine

Nicotine

Groups containing phosphorus and sulfur

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

Chemical class
Group
Formula
Structural Formula
Prefix
Suffix
Example

Phosphine
Phosphino
R3P

phosphino-
-phosphane

Methylpropylphosphane

Phosphodiester
Phosphate
HOPO(OR)2

phosphoric acid di(substituent) ester
di(substituent) hydrogenphosphate
DNA

Phosphonic acid
Phosphono
RP(=O)(OH)2

phosphono-
substituent phosphonic acid

Benzylphosphonic acid

Phosphate
Phosphate
ROP(=O)(OH)2

phospho-


Glyceraldehyde 3-phosphate

Sulfide or thioether

RSR’

di(substituent) sulfide

Dimethyl sulfide

Sulfone
Sulfonyl
RSO2R’

sulfonyl-
di(substituent) sulfone

Dimethyl sulfone
(Methylsulfonylmethane)

Sulfonic acid
Sulfo
RSO3H

sulfo-
substituent sulfonic acid

Benzenesulfonic acid

Sulfoxide
Sulfinyl
RSOR’

sulfinyl-
di(substituent) sulfoxide

Diphenyl sulfoxide

Thiol
Sulfhydryl
RSH

mercapto-, sulfanyl-
-thiol

Ethanethiol
(Ethyl mercaptan)

Thiocyanate
Thiocyanate
RSCN

thiocyanato-
alkyl thiocyanate

Disulfide
Disulfide
RSSR’

alkyl alkyl disulfide

Diphenyl disulfide
1,2-diphenyldisulfane

Other

  • For a list of all functional groups: Category:Functional groups

References

  1. ^ Compendium of Chemical Terminology (IUPAC “Gold Book”) http://goldbook.iupac.org/F02555.html
  2. ^ March, Jerry (1985). Advanced Organic Chemistry, Reactions, Mechanisms and Structure, third Edition, John Wiley & Sons. ISBN 0-471-85472-7
  3. ^ Schleselmann, L. (2004), Pharmacy Times, “Pharmacological History Notes”, http://www.pharmacytimes.com/issues/articles/2004-06_121.asp accessed 5/1/08

External links

  • IUPAC Blue Book (organic nomenclature)
  • IUPAC ligand abbreviations (pdf)
  • Organic Chemistry Help: Functional Groups Flashcards

v • d • e

Functional groups

Chemical class: Alcohol • Aldehyde • Alkane • Alkene • Alkyne • Amide • Amine • Azo compound • Benzene derivative • Carboxylic acid • Cyanate • Disulfide • Ester • Ether • Haloalkane • Hydrazone • Imine • Isocyanide • Isocyanate • Ketone • Oxime • Nitrile • Nitro compound • Nitroso compound • Peroxide • Phosphoric acid • Pyridine derivative • Sulfone • Sulfonic acid • Sulfoxide • Thioester • Thioether • Thiol

v • d • e

Concepts in organic chemistry

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

Retrieved from “http://en.wikipedia.org/wiki/Functional_group
Categories: Functional groups | Organic compounds

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