Functional group

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. When the group of covalently bound atoms bears a net charge, the group is referred to more properly as a polyatomic ion or a complex ion. Any subgroup of atoms of a compound also may be called a radical, and if a covalent bond is broken homolytically, the resulting fragment radicals are referred as free radicals.

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

Synthetic chemistry

An aldol reaction of acetone with another ketone is inefficient, because it can self-condense as well. The problem can be circumvented by replacing the ketone with the corresponding silyl enol ether in a Mukaiyama aldol addition. The silicon is then removed.

Organic reactions are facilitated and controlled by the functional groups of the reactants. In general, alkyls are unreactive and difficult to get to react selectively at the desired positions, with few exceptions. In contrast, unsaturated carbon functional groups, and carbon-oxygen and carbon-nitrogen functional groups have a more diverse array of reactions that are also selective. It may be necessary to create a functional group in the molecule to make it react. For example, to synthesize iso-octane (the 8-carbon ideal gasoline) from the unfunctionalized alkane isobutane (a 4-carbon gas), isobutane is first dehydrogenated into isobutene. This contains the alkene functional group and can now dimerize with another isobutene to give iso-octene, which is then catalytically hydrogenated to iso-octane using pressured hydrogen gas.

Functionalization

Functionalization is the addition of functional groups onto the surface of a material by chemical synthesis methods. The functional group added can be subjected to ordinary synthesis methods to attach virtually any kind of organic compound onto the surface. Functionalization is employed for surface modification of industrial materials in order to achieve desired surface properties such as water repellent coatings for automobile windshields and non-biofouling, hydrophilic coatings for contact lenses. In addition, functional groups are used to covalently link functional molecules to the surface of chemical and biochemical devices such as microarrays and microelectromechanical systems. Catalysts can be attached to a material that has been functionalized. For example, silica is functionalized with an alkyl silicone, wherein the alkyl contains an amine functional group. A ligand such as an EDTA fragment is synthesized onto the amine, and a metal cation is complexed into the EDTA fragment. The EDTA is not adsorbed onto the surface, but connected by a permanent chemical bond. Functional groups are also used to covalently link molecules such as fluorescent dyes, nanoparticles, proteins, DNA, and other compounds of interest for a variety of applications such as sensing and basic chemical research.

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, 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
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)

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 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 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
Methanol
Ketone Carbonyl RCOR' -oyl- (-COR')
or
oxo- (=O)
-one
Butanone
(Methyl ethyl ketone)
Aldehyde Aldehyde RCHO formyl- (-COH)
or
oxo- (=O)
-al
Acetaldehyde
(Ethanal)
Acyl halide Haloformyl RCOX carbonofluoridoyl-
carbonochloridoyl-
carbonobromidoyl-
carbonoiodidoyl-
-oyl halide
Acetyl chloride
(Ethanoyl chloride)
Carbonate Carbonate ester ROCOOR (alkoxycarbonyl)oxy- alkyl carbonate
Triphosgene
(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-
or
alkoxycarbonyl
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
(Ethoxyethane)
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
1,2-Methylenedioxybenzene
(1,3-Benzodioxole)
Orthocarbonate ester Orthocarbonate ester C(OR)(OR')(ORʺ)(OR) tetralkoxy- tetraalkyl orthocarbonate

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-
or
carbamoyl-
-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
Ethanimine
Secondary aldimine RC(=NR')H imino- -imine
Imide Imide (RCO)2NR' imido- -imide
Succinimide
(Pyrrolidine-2,5-dione)
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
Methyl cyanate
Isocyanate RNCO isocyanato- alkyl isocyanate
Methyl isocyanate
Nitrate Nitrate RONO2 nitrooxy-, nitroxy-

alkyl nitrate


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

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

Methyl isocyanide
Nitrite Nitrosooxy RONO nitrosooxy-

alkyl nitrite


Isoamyl nitrite
(3-methyl-1-nitrosooxybutane)
Nitro compound Nitro RNO2 nitro-  
Nitromethane
Nitroso compound Nitroso RNO nitroso- (Nitrosyl-)  
Nitrosobenzene
Oxime Oxime RCH=NOH   Oxime
Acetone oxime
(2-Propanone oxime)
Pyridine derivative Pyridyl RC5H4N




4-pyridyl
(pyridin-4-yl)

3-pyridyl
(pyridin-3-yl)

2-pyridyl
(pyridin-2-yl)

-pyridine
Nicotine

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 sulfanyl-
(-SH)
-thiol
Ethanethiol
Sulfide
(Thioether)
Sulfide RSR' substituent sulfanyl-
(-SR')
di(substituent) sulfide


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


(Methyldisulfanyl)methane (prefix) or
Dimethyl disulfide (suffix)
Sulfoxide Sulfinyl RSOR' -sulfinyl-
(-SOR')
di(substituent) sulfoxide
(Methanesulfinyl)methane (prefix) or
Dimethyl sulfoxide (suffix)
Sulfone Sulfonyl RSO2R' -sulfonyl-
(-SO2R')
di(substituent) sulfone
(Methanesulfonyl)methane (prefix) or
Dimethyl sulfone (suffix)
Sulfinic acid Sulfino RSO2H sulfino-
(-SO2H)
-sulfinic acid
2-Aminoethanesulfinic acid
Sulfonic acid Sulfo RSO3H sulfo-
(-SO3H)
-sulfonic acid
Benzenesulfonic acid
Thiocyanate Thiocyanate RSCN thiocyanato-
(-SCN)
substituent thiocyanate
Phenyl thiocyanate
Isothiocyanate RNCS isothiocyanato-
(-NCS)
substituent isothiocyanate
Allyl isothiocyanate
Thione Carbonothioyl RCSR' -thioyl-
(-CSR')
or
sulfanylidene-
(=S)
-thione
Diphenylmethanethione
(Thiobenzophenone)
Thial Carbonothioyl RCSH methanethioyl-
(-CSH)
or
sulfanylidene-
(=S)
-thial

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 phosphanyl- -phosphane
Methylpropylphosphane
Phosphonic acid Phosphono RP(=O)(OH)2 phosphono- substituent phosphonic acid
Benzylphosphonic acid
Phosphate Phosphate ROP(=O)(OH)2 phosphonooxy-
or
O-phosphono- (phospho-)
substituent phosphate
Glyceraldehyde 3-phosphate (suffix)

O-Phosphonocholine (prefix)
(Phosphocholine)
Phosphodiester Phosphate HOPO(OR)2 [(alkoxy)hydroxyphosphoryl]oxy-
or
O-[(alkoxy)hydroxyphosphoryl]-
di(substituent) hydrogen phosphate
or
phosphoric acid di(substituent) ester
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 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 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").[3]

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

Chemical class Group Formula Structural Formula Prefix Suffix Example
Single bond R• Ylo-[5] -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

External links

This article is issued from Wikipedia - version of the Wednesday, May 04, 2016. The text is available under the Creative Commons Attribution/Share Alike but additional terms may apply for the media files.