ACD/Name

Free Radicals, Ions, and Radical Ions

Cations Rule C-82

82.1 - If the positive charge of a parent organic cation is derived by fixation of a proton on a hetero atom that does not form part of a ring, the ion is named as a substitution product of the parent cation named in Table C-V. When a halogen cation is present as a ring member, the remainder of the ring may be named as a bivalent substituent therein.

Examples to Rule C-82.1

Tetramethylammonium
Dimethyloxonium
Diphenyliodonium
Ethylenebromonium

Exceptions: Names of the type benzenediazonium (Rule C-931), uronium (Rule C-973), and thiouronium (Rule C-974) are used as laid down in the Rules cited.

82.2 - If the positive charge of an organic cation is derived by fixation of a proton on a hetero atom of a parent compound whose name does not end in amine, the name of the ion is formed by adding "-ium" to the name of the organic parent compound, with elision of a terminal "e" (if present). When there is more than one hetero atom able to fix the proton, the point of attachment of the proton may be shown by the "indicated hydrogen" method.

Examples to Rule C-82.2

Anilinium
Guanidinium
2-Phenylhydrazinium
1-Methylhydrazinium

(for numbering see Rule C-921.5)
Acetonium
1,4-Dioxanium
1-Methylpyridinium
Imidazolium
Glycinium
Prolinium
1,4-Dithian-2-iminium
9aH-Quinolizinium

82.3 - When replacement ("a") nomenclature is used (see Rule B-6) the ending "-a" of an affix oxa, thia, aza, etc., is changed to "-onia".

Example to Rule C-82.3

82.4 - An organic cation formed by addition of a proton to an unsaturated hydrocarbon is named by adding "-ium" to the name of the hydrocarbon, with elision of terminal "e" if present. If desired the point of attachment of the proton is shown by the "indicated hydrogen" method. If a -complex is to be specified, the prefix is used. If the position of the charge is to be specified, the appropriate locant is placed before the ending "-ium".

Examples to Rule C-82.4

Ethenium
Benzenium
Allenium
(position of unknown)
Heptamethylbenzenium
6H-Azulenium

See Recommendations'93 R-5.8.2

Next:
Cations
Rule C-83
Anions
Rule C-84
Two or More Kinds of Ionic Centre with the Same Kind of Charge in a Single Structure>
Rule C-85
Rule C-86
Positive and Negative Ionic Centres in a Single Structure
Rule C-87

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This HTML reproduction of Sections A, B and C of IUPAC "Blue Book" is as close as possible to the published version [see Nomenclature of Organic Chemistry, Sections A, B, C, D, E, F, and H, Pergamon Press, Oxford, 1979. Copyright 1979 IUPAC.] If you need to cite these rules please quote this reference as their source.

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