Functional group

Group of atoms giving a molecule characteristic properties From Wikipedia, the free encyclopedia

Functional group

In organic chemistry, a functional group is any 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.

Thumb
Example functional groups of benzyl acetate:
  Ester group
  Acetyl group
  Benzyloxy group

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 not 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

Summarize
Perspective

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.

More information , ...
Chemical class Group Formula Structural Formula Prefix Suffix Example
AlkaneAlkyl R(CH2)nH Thumb alkyl--ane Thumb
Ethane
AlkeneAlkenyl R2C=CR2 Thumb alkenyl--ene Thumb
Ethylene
(Ethene)
AlkyneAlkynyl RC≡CR′ alkynyl--yne
Acetylene
(Ethyne)
Benzene derivative Phenyl RC6H5
RPh
Thumb phenyl--benzene Thumb
Cumene
(Isopropylbenzene)
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There are also a large number of branched or ring alkanes that have specific names, e.g., tert-butyl, bornyl, cyclohexyl, etc. There are several functional groups that contain an alkene such as vinyl group, allyl group, or acrylic group. 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.

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Chemical class Group Formula Structural formula Prefix Suffix Example
haloalkanehalo RX halo-alkyl halide Thumb
Chloroethane
(Ethyl chloride)
fluoroalkanefluoro RF fluoro-alkyl fluoride Thumb
Fluoromethane
(Methyl fluoride)
chloroalkanechloro RCl chloro-alkyl chloride Thumb
Chloromethane
(Methyl chloride)
bromoalkanebromo RBr bromo-alkyl bromide Thumb
Bromomethane
(Methyl bromide)
iodoalkaneiodo RI iodo-alkyl iodide Thumb
Iodomethane
(Methyl iodide)
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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).

More information Chemical class, Group ...
Chemical class Group Formula Structural formula Prefix Suffix Example
Alcohol Hydroxyl ROH
Hydroxyl
Hydroxyl
hydroxy--ol Thumb
Methanol
KetoneKetone RCOR′ Thumb -oyl- (-COR′)
or
oxo- (=O)
-one Thumb
Butanone
(Methyl ethyl ketone)
AldehydeAldehyde RCHO Thumb formyl- (-COH)
or
oxo- (=O)
-al Thumb
Acetaldehyde
(Ethanal)
Acyl halideHaloformyl RCOX Thumb carbonofluoridoyl-
carbonochloridoyl-
carbonobromidoyl-
carbonoiodidoyl-
-oyl fluoride
-oyl chloride
-oyl bromide
-oyl iodide
Thumb
Acetyl chloride
(Ethanoyl chloride)
Carbonate Carbonate ester ROCOOR′ Thumb (alkoxycarbonyl)oxy- alkyl carbonate Thumb
Triphosgene
(bis(trichloromethyl) carbonate)
Carboxylate CarboxylateRCOO
Carboxylate
Carboxylate

Thumb
carboxylato--oate Thumb
Sodium acetate
(Sodium ethanoate)
Carboxylic acid CarboxylRCOOH Thumb carboxy--oic acid Thumb
Acetic acid
(Ethanoic acid)
EsterCarboalkoxy RCOOR′ Thumb alkanoyloxy-
or
alkoxycarbonyl
alkyl alkanoate Thumb
Ethyl butyrate
(Ethyl butanoate)
Hydroperoxide Hydroperoxy ROOH Thumb hydroperoxy- alkyl hydroperoxide Thumb
tert-Butyl hydroperoxide
Peroxide Peroxy ROOR′ Thumb peroxy- alkyl peroxide Thumb
Di-tert-butyl peroxide
EtherEther ROR′
Ether
Ether
alkoxy- alkyl ether Thumb
Diethyl ether
(Ethoxyethane)
HemiacetalHemiacetal R2CH(OR1)(OH) Thumb alkoxy -ol -al alkyl hemiacetal
HemiketalHemiketal RC(ORʺ)(OH)R′ Thumb alkoxy -ol -one alkyl hemiketal
AcetalAcetal RCH(OR′)(OR″) Thumb dialkoxy- -al dialkyl acetal
Ketal (or Acetal)Ketal (or Acetal) RC(OR″)(OR‴)R′ Thumb dialkoxy- -one dialkyl ketal
OrthoesterOrthoester RC(OR′)(OR″)(OR‴) Thumb trialkoxy-
Heterocycle
(if cyclic)
Methylenedioxy (–OCH2O–)

methylenedioxy- -dioxole Thumb
1,2-Methylenedioxybenzene
(1,3-Benzodioxole)
Orthocarbonate esterOrthocarbonate ester C(OR)(OR′)(OR″)(OR‴) Thumb tetralkoxy- tetraalkyl orthocarbonate Thumb
Tetramethoxymethane
Organic acid anhydrideCarboxylic anhydride R1(CO)O(CO)R2 Thumb anhydride Thumb
Butyric anhydride
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Groups containing nitrogen

Compounds that contain nitrogen in this category may contain C-O bonds, such as in the case of amides.

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Chemical class Group Formula Structural formula Prefix Suffix Example
AmideCarboxamide RCONR'R" Thumb carboxamido-
or
carbamoyl-
-amide Thumb
Acetamide
(Ethanamide)
Amidine Amidine R4C(NR1)(NR2R3) Thumb amidino- -amidine Thumbacetamidine

(acetimidamide)

Guanidine Guanidine RNC(NR2)2) Thumb Guanidin- -Guanidine ThumbGuanidinopropionic acid
Amines Primary amine RNH2 Thumb amino--amine Thumb
Methylamine
(Methanamine)
Secondary amine R'R"NH Thumb amino--amine Thumb
Dimethylamine
Tertiary amine R3N Thumb amino--amine Thumb
Trimethylamine
4° ammonium ion R4N+ Thumb ammonio--ammonium Thumb
Choline
Hydrazone R'R"CN2H2
Thumb
hydrazino- -hydrazine
Thumb
Benzophenone
Imine Primary ketimine RC(=NH)R' Thumb imino--imine
Secondary ketimine Thumb imino--imine
Primary aldimine RC(=NH)H Thumb imino--imine Thumb
Ethanimine
Secondary aldimine RC(=NR')H Thumb imino--imine
ImideImide (RCO)2NR' Thumb imido- -imide Thumb
Succinimide
(Pyrrolidine-2,5-dione)
Azide Azide RN3 Thumb azido-alkyl azide Thumb
Phenyl azide
(Azidobenzene)
Azo compound Azo
(Diimide)
RN2R' Thumb azo--diazene Thumb
Methyl orange
(p-dimethylamino-azobenzenesulfonic acid)
Cyanates CyanateROCN Thumb cyanato- alkyl cyanate Thumb
Methyl cyanate
IsocyanateRNCO Thumb isocyanato- alkyl isocyanate Thumb
Methyl isocyanate
NitrateNitrate RONO2 Thumb nitrooxy-, nitroxy-

alkyl nitrate

Thumb
Amyl nitrate
(1-nitrooxypentane)
Nitrile Nitrile RCN cyano- alkanenitrile
alkyl cyanide
Thumb
Benzonitrile
(Phenyl cyanide)
IsonitrileRNC
Thumb
isocyano- alkaneisonitrile
alkyl isocyanide

Methyl isocyanide
NitriteNitrosooxy RONO Thumb nitrosooxy-

alkyl nitrite

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

Thumb
Thumb
Thumb

4-pyridyl
(pyridin-4-yl)

3-pyridyl
(pyridin-3-yl)

2-pyridyl
(pyridin-2-yl)

-pyridine Thumb
Nicotine
Carbamate ester CarbamateRO(C=O)NR2 Thumb (-carbamoyl)oxy--carbamate Thumb
Chlorpropham
(Isopropyl (3-chlorophenyl)carbamate)
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Groups containing sulfur

Compounds that contain sulfur exhibit unique chemistry due to sulfur's ability to form more bonds than oxygen, its 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.

More information Chemical class, Group ...
Chemical class Group Formula Structural formula Prefix Suffix Example
Thiol Sulfhydryl RSH Thumb sulfanyl-
(-SH)
-thiol Thumb
Ethanethiol
Sulfide
(Thioether)
Sulfide RSR' Thumb substituent sulfanyl-
(-SR')
di(substituent) sulfide
Thumb

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

(Methyldisulfanyl)methane (prefix) or
Dimethyl disulfide (suffix)
Sulfoxide Sulfinyl RSOR' Thumb -sulfinyl-
(-SOR')
di(substituent) sulfoxide Thumb
(Methanesulfinyl)methane (prefix) or
Dimethyl sulfoxide (suffix)
Sulfone Sulfonyl RSO2R' Thumb -sulfonyl-
(-SO2R')
di(substituent) sulfone Thumb
(Methanesulfonyl)methane (prefix) or
Dimethyl sulfone (suffix)
Sulfinic acidSulfino RSO2H Thumb sulfino-
(-SO2H)
-sulfinic acid Thumb
2-Aminoethanesulfinic acid
Sulfonic acidSulfo RSO3H Thumb sulfo-
(-SO3H)
-sulfonic acid Thumb
Benzenesulfonic acid
Sulfonate esterSulfo RSO3R' Thumb (-sulfonyl)oxy-
or
alkoxysulfonyl-
R' R-sulfonate Thumb
Methyl trifluoromethanesulfonate or
Methoxysulfonyl trifluoromethane (prefix)
Thiocyanate ThiocyanateRSCN Thumb thiocyanato-
(-SCN)
substituent thiocyanate Thumb
Phenyl thiocyanate
IsothiocyanateRNCS Thumb isothiocyanato-
(-NCS)
substituent isothiocyanate Thumb
Allyl isothiocyanate
Thioketone Carbonothioyl RCSR' Thione -thioyl-
(-CSR')
or
sulfanylidene-
(=S)
-thione Thumb
Diphenylmethanethione
(Thiobenzophenone)
Thial Carbonothioyl RCSH Thial methanethioyl-
(-CSH)
or
sulfanylidene-
(=S)
-thial
Thiocarboxylic acid Carbothioic S-acid RC=OSH
Thioic S-acid
Thioic S-acid
mercaptocarbonyl- -thioic S-acid Thumb
Thiobenzoic acid
(benzothioic S-acid)
Carbothioic O-acid RC=SOH
Thioic O-acid
Thioic O-acid
hydroxy(thiocarbonyl)- -thioic O-acid
Thioester Thiolester RC=OSR' Thumb S-alkyl-alkane-thioate Thumb
S-methyl thioacrylate
(S-methyl prop-2-enethioate)
Thionoester RC=SOR' Thumb O-alkyl-alkane-thioate
Dithiocarboxylic acid Carbodithioic acid RCS2H
Dithiocarboxylic acid
Dithiocarboxylic acid
dithiocarboxy- -dithioic acid Thumb
Dithiobenzoic acid
(Benzenecarbodithioic acid)
Dithiocarboxylic acid ester Carbodithio RC=SSR' Thumb -dithioate
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Groups containing phosphorus

Compounds that contain phosphorus exhibit unique chemistry due to the ability of phosphorus to form more bonds than nitrogen, its lighter analogue on the periodic table.

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Chemical class Group Formula Structural formula Prefix Suffix Example
Phosphine
(Phosphane)
Phosphino R3P Thumb phosphanyl--phosphane Thumb
Methylpropylphosphane
Phosphonic acid Phosphono Thumb phosphono- substituent phosphonic acid Thumb
Benzylphosphonic acid
Phosphate Phosphate Thumb phosphonooxy-
or
O-phosphono- (phospho-)
substituent phosphate Thumb
Glyceraldehyde 3-phosphate (suffix)
Thumb
O-Phosphonocholine (prefix)
(Phosphocholine)
Phosphodiester Phosphate HOPO(OR)2 Thumb [(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)
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Groups containing boron

Compounds containing boron exhibit unique chemistry due to their having partially filled octets and therefore acting as Lewis acids.

More information Chemical class, Group ...
Chemical classGroupFormulaStructural formulaPrefixSuffixExample
Boronic acidBoronoRB(OH)2
Thumb
Borono-substituent
boronic acid
Boronic esterBoronateRB(OR)2
Thumb
O-[bis(alkoxy)alkylboronyl]-substituent
boronic acid
di(substituent) ester
Borinic acidBorinoR2BOH
Thumb
Hydroxyborino-di(substituent)
borinic acid
Borinic esterBorinateR2BOR
Thumb
O-[alkoxydialkylboronyl]-di(substituent)
borinic acid
substituent ester
Thumb
Diphenylborinic acid 2-aminoethyl ester
(2-Aminoethoxydiphenyl borate)
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Groups containing metals

More information Chemical class, Structural formula ...
Chemical class Structural formula Prefix Suffix Example
Alkyllithium RLi (tri/di)alkyl- -lithium Thumb

methyllithium

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

methylmagnesium chloride

Alkylaluminium Al2R6 -aluminium Thumb

trimethylaluminium

Silyl ether R3SiOR -silyl ether Thumb

trimethylsilyl triflate

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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 methylidene 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.

More information Chemical class, Group ...
Chemical classGroupFormulaStructural formulaPrefixSuffixExample
Single bondR•Ylo-[6]-yl
Double bondR: ?-ylidene
Triple bondR⫶ ?-ylidyne
Carboxylic acyl radicalAcylR−C(=O)• ?-oyl
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See also

References

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