Aminoxyl denotes a
radical
Radical may refer to:
Politics and ideology Politics
*Radical politics, the political intent of fundamental societal change
*Radicalism (historical), the Radical Movement that began in late 18th century Britain and spread to continental Europe and ...
functional group with general structure R
2N–O
•. It is commonly known as a nitroxyl radical or a nitroxide, however
IUPAC discourages the use of these terms, as they erroneously suggest the presence of a
nitro group. Aminoxyls are structurally related to
hydroxylamines
Hydroxylamine is an inorganic compound with the formula . The material is a white crystalline, hygroscopic compound.Greenwood and Earnshaw. ''Chemistry of the Elements.'' 2nd Edition. Reed Educational and Professional Publishing Ltd. pp. 431–43 ...
and
''N''-oxoammonium salts, with which they can interconvert via a series of
redox steps.
Aminoxyl radical.svg, The general structure of the aminoxyl radical
2,2,6,6-Tetramethylpiperidinyloxyl.svg, TEMPO, a commonly encountered organic aminoxyl radical
Kaliumnitrosodisulfonat.svg, Fremy's salt, an inorganic aminoxyl radical
Sterically unhindered aminoxyls baring α-hydrogens are unstable and undergo rapid
disproportionation to
nitrone
In organic chemistry, a nitrone is a functional group consisting of an ''N''-oxide of an imine. The general structure is , where R’ is not a hydrogen. A nitrone is a 1,3-dipole, and is used in 1,3-dipolar cycloadditions. Other reactions of ...
s and
hydroxylamines. Sterically hindered aminoxyls without α-hydrogens, such
TEMPO and
TEMPOL, and are persistent (stable) radicals and find use in a range of applications, both on the laboratory scale and in industry. Their ability to reversibly bind to other radical compounds makes them important as both
spin labels and
spin traps. They are used to selectively oxidise carbonyl groups via
oxoammonium-catalyzed oxidations. They are also used as
polymer stabilizers such as
hindered amine light stabilizers or as transient reactive species in
''p''-phenylenediamine based
antiozonants.
They are used both to form polymers via
nitroxide-mediated radical polymerization and prevent their formation as
polymerization inhibitors. Various other reagents, such as
''N''-hydroxyphthalimide can also be converted into aminoxyl radicals as part of their chemistry.
See also
*
Nitrone
In organic chemistry, a nitrone is a functional group consisting of an ''N''-oxide of an imine. The general structure is , where R’ is not a hydrogen. A nitrone is a 1,3-dipole, and is used in 1,3-dipolar cycloadditions. Other reactions of ...
— structurally related, an ''N''-oxide of an imine
References
{{Reflist
Functional groups
Free radicals