Names of ions and radicals

The charges of the atoms need not be specified in a stoichiometric name. In many cases, however, atoms or groups of atoms are known to carry a particular charge. Within compositional nomenclature, the name of a compound can include the names of individual ions constructed as stoichiometric names or according to other principles, as described below. 

A cation is a monoatomic or polyatomic species having one or more positive charges. The charge on a cation can be indicated in names by using the charge number or, in the case of additively named cations, by the oxidation number(s) of the central atom or atoms. Oxidation and charge numbers are discussed in Section IR-5.4.2.2. 

The name of a monoatomic cation is that of the element with an appropriate charge number appended in parentheses. Unpaired electrons in monoatomic cations may be indicated using a radical dot, i.e. a centred dot placed in front of the charge, preceded by a number if necessary. 

Homopolyatomic cations are named by adding the charge number to the stoichiometric name of the corresponding neutral species, i.e. the element name with the appropriate multiplicative prefix. Radical dots may be added to indicate the presence of unpaired electrons. 

---

IR-5.2 Stoichiometric names of elements and binary compounds IR-5.3 Names of ions and radicals IR-5.3.1 General IR-5.3.2 Cations IR-5.3.2.1 General IR-5.3.2.2 Monoatomic cations IR-5.3.2.3 Homopolyatomic cations IR-5.3.2.4 Heteropolyatomic cations IR-5.3.3 Anions IR-5.3.3.1 Overview IR-5.3.3.2 Monoatomic anions IR-5.3.3.3 Homopolyatomic anions IR-5.3.3.4 Heteropolyatomic anions IR-5.4 Generalized stoichiometric names... 

IR-6.2.4.1 Heteronuclear acyclic parent hydrides in general IR-6.2.4.2 Hydrides consisting of chains of alternating skeletal atoms IR-6.2.4.3 Heteronuclear monocyclic parent hydrides Hantzsch-Widman nomenclature IR-6.2.4.4 Skeletal replacement in boron hydrides IR-6.2.4.5 Heteronuclear polycyclic parent hydrides IR-6.3 Substitutive names of derivatives of parent hydrides IR-6.3.1 Use of suffixes and prefixes IR-6.3.2 Hydrogen substitution in boron hydrides IR-6.4 Names of ions and radicals derived from parent hydrides... 

This section presents names of ions and radicals that can be formally derived from hydrides by the operations of removal or addition of hydrogen atoms, hydride ions or hydrons. A great many ions and radicals can also be named by additive methods, as described in Chapter IR-7. Many simple ions and radicals are named in Table IX, often by both nomenclature types. 

Anionic species take the ending ate in additive nomenclature, whereas no distinguishing termination is used for cationic or neutral species. Additive names of ions end with the charge number (see Section IR-5.4.2.2). In additive names of radicals, the radical character of the compound may be indicated by a radical dot, , added in parentheses and centred, after the name of the compound. Polyradicals are indicated by the appropriate numeral placed before the dot. For example, a diradical is indicated by (2 ) . 

The radical and the anion, R-N2 and R-N2, derived (formally) from a diazonium ion by addition of one and two electrons respectively, are named as diazenyl ( radical at the end is not necessary ) and diazenide (IUPAC, 1993). The radical derived formally from a diazoalkane by addition of a hydrogen atom (R=N-NH) is named diazanyl . In order to be consistent with the nomenclature of diazonium ions, the name of the parent compound should precede the words mentioned, e. g., benzenediazenyl for C6H5 - NJ (the term phenyldiazenyl radical is, however, used by Chemical Abstracts). 

On the basis of all these results and his own investigations on chloro- and bromo-de-diazoniations (Galli, 1981), Galli proposed in 1988 that iodo-de-diazoniation, after formation of the aryl radical in the initiation reaction (Scheme 10-22) follows three coupled iodination chain reactions based on the formation of the I2 molecule and the If anion in the step shown in Scheme 10-23, namely iodine atom (I ) addition (Scheme 10-24), and iodine abstraction from I2 and If in Schemes 10-25 and 10-26 respectively. Aryl radicals and iodine molecules are regenerated as indicated in Scheme 10-27. The addition of iodide ion to aryl radicals forming the radical anion [Arl] -, as in Scheme 10-28, is considered an unlikely pathway, as that reaction has been found to be reversible (Lawless and Hawley, 1969 Andrieux et al. 1979). 

The situation is not as clearly solved in a positive or negative sense for arenediazo phenyl ethers. Here three alternatives have to be considered, namely an intramolecular rearrangement of the arenediazo phenyl ether (Scheme 12-11, A), and two types of intermolecular rearrangement, either by heterolytic dissociation into a diazonium ion and a phenoxide ion (B) or by homolytic dissociation into a radical pair or two free radicals (C). 

Some of the reports are as follows. Mizukoshi et al. [31] reported ultrasound assisted reduction processes of Pt(IV) ions in the presence of anionic, cationic and non-ionic surfactant. They found that radicals formed from the reaction of the surfactants with primary radicals sonolysis of water and direct thermal decomposition of surfactants during collapsing of cavities contribute to reduction of metal ions. Fujimoto et al. [32] reported metal and alloy nanoparticles of Au, Pd and ft, and Mn02 prepared by reduction method in presence of surfactant and sonication environment. They found that surfactant shows stabilization of metal particles and has impact on narrow particle size distribution during sonication process. Abbas et al. [33] carried out the effects of different operational parameters in sodium chloride sonocrystallisation, namely temperature, ultrasonic power and concentration sodium. They found that the sonocrystallization is effective method for preparation of small NaCl crystals for pharmaceutical aerosol preparation. The crystal growth then occurs in supersaturated solution. Mersmann et al. (2001) [21] and Guo et al. [34] reported that the relative supersaturation in reactive crystallization is decisive for the crystal size and depends on the following factors. 

At 300 K and below, when hydroperoxides are stable, the decay of PMP peroxyl radicals gives rise to low-molecular-weight products, namely, water, acetone, and isobutyric aldehyde. The formation of these products can be explained by the breakdown of various peroxyl radicals with production of hydroxyl ion and cleavage of the C—C bond. 

We mentioned in Section III.A that one of the unique features of radical ion optical spectroscopy is that it allows one to measure excited-state energies of a molecule at two different geometries, namely that of the neutral species (If in PE spectra) and that of the relaxed radical cation (Xmax of the EA bands). In many cases this feature is of little relevance because either the geometry changes upon ionization are too small to lead to noticeable effects (e.g. in aromatic hydrocarbons), or because such effects are obscured, due to the invisibility of the states in one or other of the two experiments (i.e. strong cr-ionizations in the PE spectrum) or because of the near-cancellation of opposing effects (as in the case of linear conjugated polyene radical cations). 

Also other Type B and C series from Table II are consistent with the above elimination mechanisms. The dehydration rate of the alcohols ROH on an acid clay (series 16) increased with the calculated inductive effect of the group R. For the dehydrochlorination of polychloroethanes on basic catalysts (series 20), the rate could be correlated with a quantum-chemical reactivity index, namely the delocalizability of the hydrogen atoms by a nucleophilic attack similar indices for a radical or electrophilic attack on the chlorine atoms did not fit the data. The rates of alkylbenzene cracking on silica-alumina catalysts have been correlated with the enthalpies of formation of the corresponding alkylcarbonium ions (series 24). Similar correlations have been obtained for the dehydrosulfidation of alkanethiols and dialkyl sulfides on silica-alumina (series 36 and 37) in these cases, correlation by the Taft equation is also possible. The rate of cracking of 1,1-diarylethanes increased with the increasing basicity of the reactants (series 33). 

ESR methods unambiguously establishes the presence of species bearing unpaired electrons (ion-radicals and radicals). The ESR spectrum quantitatively characterizes the distribution of electron density within the paramagnetic particle by a hyperfine structure of ESR spectra. This establishes the nature and electronic configuration of the particle. A review by Davies (2001) is highly recommended as a guide to current practice for ESR spectroscopic studies (this quotation is from the title of the review). The ESR method dominates in ion-radical studies. Its modern modifications, namely, ENDOR and electron-nuclear-nuclear triple resonance (TRIPLE) and special methods to observe ion-radicals by swiftness or stealth are described in special literatures (Moebius and Biehl 1979, Kurreck et al. 1988, Werst and Trifunac 1998). 

---