ACD/Name

Specific Classes of Compounds

R-5.8.1 Radicals

R-5.8.1.1 Monovalent radicals. A radical formally derived by the removal of one hydrogen atom from any of the mononuclear parent hydrides of the carbon family of elements, or from a terminal atom of a saturated unbranched acyclic hydrocarbon, or from any position of a monocyclic hydrocarbon ring is named by replacing the "-ane" ending of the systematic name of the parent hydride by "-yl".

Examples to R-5.8.1.1

A radical formally derived by the removal of one hydrogen atom from any position of any other parent hydride, is named by adding the suffix "-yl" to the name of the parent hydride, eliding the final "e" of the name of the parent hydride, if present.

Examples to R-5.8.1.1

Note: As exceptions, the names of the radicals and are "hydroxyl" and "hydroperoxyl", respectively.

R-5.8.1.2 Divalent and trivalent radicals. Divalent radical centres formally derived by removal of two hydrogen atoms from the mononuclear parent hydrides CH4, NH3, and SiH4 may be named respectively "methylene" or "carbene"; "azanylidene", "nitrene", or "aminylene"; an "silylene". Derivatives of these parent hydride radicals are named substitutively.

Note: The use of these names does not imply a specific electronic configuration. If needed, such a distinction should be made by using a separate word or descriptive phrase, such as singlet and triplet.

Examples to R-5.8.1.2

Other bivalent radical centres and trivalent radicals centres formally derived by removal of two or three hydrigen atoms from the same skeletal atom of a parent hydride may be described by adding a suffix "-ylidene" or "-ylidyne" following the procedure prescribed above for the suffix "-yl" (see R-5.8.1.1).

Examples to R-5.8.1.2

Polyradicals containing two or more radical centres, formally derived by the removal of two or more hydrogen atoms from each of two or more different skeletal atoms of a parent hydride, are named by adding to the name of the parent hydride combinations of the suffixes "-yl" for a monovalent radical centre, "-ylidene" for a divalent radical centre, and "-ylidyne" for a trivalent radical centre, together with the appropriate numerical prefixes indicating the number of each kind of radical centre. The final "e" of the name of the parent hydride, if present, is elided when followed by the letter "y".

Examples to R-5.8.1.2

The presence of a radical centre in a substituent to be cited as a prefix is expressed by the prefix "ylo-" denoting the removal of a hydrogen atom.

Example to R-5.8.1.2

R-5.8.1.3 Radical centres on characteristic groups. Acyl radicals, i.e., radicals with at least one chalcogen or nitrogen atom attached to the radical centre by a (formal) double bond, which may be considered to be formally derived by the loss of the hydroxy group from acid characteristic groups, are named by replacing the "-ic acid" or "-carboxylic acid" ending of the name with "-yl" (occasionally "-oyl") or "-carbonyl". Alternatively, acyl radicals may be named on the basis of an appropriate parent hydride using prefixes such as "oxo-", "thioxo-", "imino-", etc.

Examples to R-5.8.1.3

A radical derived formally by the removal of one or two hydrogen atoms from an amine, imine, or amide characteristic group may be named by adding a suffix "-aminyl", "-iminyl", or "-amidyl", to the name of the parent hydride for monovalent radicals and as a substituted nitrene for bivalent radicals. Alternatively, such radicals may be named substitutively on the basis of the parent hydride "azane".

Examples to R-5.8.1.3

Polyradicals with radical centres identically derived located on two or more amine, imine, or amide characteristic groups are named by applying the principles for nomenclature of assemblies of identical units using the multiplicative prefixes "bis-", "tris-", etc.

Examples to R-5.8.1.3

A radical derived formally by the removal of the hydrogen atom from the hydroxy group of an acid or hydroxy characteristic group is named on the basis of a composite parent radical name formed by combining the appropriate prefix derived from the parent hydride or acid residue attached to the chalcogen atom with the term "oxyl", "peroxyl". etc.

Examples to R-5.8.1.3

Chalcogen analogues are named on the basis of parent radicals, such as "sulfanyl" and "selanyl".

Examples to R-5.8.1.3

Next:
R-5.8.2 Cations
R-5.8.3 Anions
R-5.8.4 Cationic and anionic centres in a single structure
R-5.8.5 Radical ions

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This HTML reproduction is as close as possible to the published version [see IUPAC, Commission on Nomenclature of Organic Chemistry. A Guide to IUPAC Nomenclature of Organic Compounds (Recommendations 1993), 1993, Blackwell Scientific publications, Copyright 1993 IUPAC]. If you need to cite these rules please quote this reference as their source.

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