Editing Functional group (section)

{{Short description|Group of atoms giving a molecule characteristic properties}}
{{Other uses}}
{{More citations needed|date=August 2016}}
[[File:Benzyl acetate - functional groups and moieties.svg|thumb|150px|Example functional groups of [[benzyl acetate]]:
{{legend-line|solid red|[[Ester]] group}}
{{legend-line|dashed green|[[Acetyl]] group}} {{legend-line|dashed orange|[[Benzyl alcohol|Benzyloxy]] group}}
]]
In [[organic chemistry]], a '''functional group''' is any [[substituent]] or [[moiety (chemistry)|moiety]] in a [[molecule]] that causes the molecule's characteristic [[chemical reaction]]s. The same functional group will undergo the same or similar chemical reactions regardless of the rest of the molecule's composition.<ref>[[Compendium of Chemical Terminology]] (IUPAC "Gold Book") [http://goldbook.iupac.org/html/F/F02555.html functional group] {{Webarchive|url=https://web.archive.org/web/20190516163117/http://goldbook.iupac.org/html/F/F02555.html |date=2019-05-16 }}</ref><ref>{{March3rd}}</ref> This enables systematic prediction of chemical reactions and behavior of [[chemical compound]]s and the design of [[chemical synthesis]]. The [[Reactivity (chemistry)|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]].

A functional group is a group of atoms in a molecule with distinctive [[Chemical property|chemical properties]], regardless of the other [[atom]]s in the molecule. The atoms in a functional group are linked to each other and to the rest of the molecule by [[covalent bond]]s. For repeating units of [[polymer]]s, functional groups attach to their [[Chemical polarity|nonpolar]] core of [[carbon]] atoms and thus add chemical character to carbon chains. Functional groups can also be [[Ionization|charged]], e.g. in [[carboxylate]] salts ({{chem2|\sCOO-}}), which turns the molecule into a [[polyatomic ion]] or a [[coordination complex|complex ion]]. Functional groups binding to a central atom in a [[coordination complex]] are called ''[[ligand]]s''. 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 [[Hydroxy group|hydroxyl]] functional group ({{chem2|\sOH}}) and hydroxyls interact strongly with each other. Plus, when functional groups are more [[Electronegativity|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 solution|aqueous]] environment.

Combining the names of functional groups with the names of the parent [[alkane]]s generates what is termed a [[systematic name|systematic nomenclature]] for naming [[organic compound]]s. 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 nomenclature of organic chemistry|IUPAC convention]]s call for numeric labeling of the position, e.g. 4-aminobutanoic acid. In traditional names various qualifiers are used to label [[isomer]]s, for example, isopropanol (IUPAC name: propan-2-ol) is an isomer of n-propanol (propan-1-ol). The term [[Moiety (chemistry)|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 [[Aromaticity|aromatic ring]], regardless of how many functional groups the said aryl has.