Nomenclature number prefixes used

Meanwhile, the A convention combined with replacement nomenclature may be used to indicate the changed bonding number of the anionic site, and the suffix -ide appended, as shown in (202) and (203). Proposals for an anionic replacement prefix, analogous to the cationic -onia prefixes, are under consideration. 

The procedure for naming a compound involves some or all of the following steps, depending on the structure of the molecule under study (1) the type of nomenclature to be used (conjunctive, multiplicative, etc.) is chosen (2) the parent structure is named (3) the prefixes, suffixes, and names of funcUonal and substituent groups that were not included in (2) me attached (4) the numbering is completed. 

In Chap. 6 we placed Roman numerals at the ends of names of metals to distinguish the charges on monatomic cations. It is really the oxidation number that is in parentheses. This nomenclature system is called the Stock system. For monatomic ions, the oxidation number is equal to the charge. For other cations, again the oxidation number is used in the name. For example, Hg2 + is named mercury(I) ion. Its charge is 24- the oxidation number of each atom is 4-1. Oxidation numbers are also used for other cations, such as dioxovanadium(V) ion, V02". The prefix 0x0- stands for oxygen. Oxidation numbers can be used with nonmetal-nonmetal compounds, as in sulfur(VI) oxide for SO3, but the older system using prefixes (Table 6-2) is still used more often. 

Substitutive nomenclature (Section 4.3F) A system for naming compounds in which each atom or group, called a substituent, is cited as a prefix or suffix to a parent compound. In the lUPAC system only one group may be cited as a suffix. Locants (usually numbers) are used to tell where the group occurs. 

There is a nomenclature dilemma for cyclic alkanes. The suffix for the name must be ane because they are alkanes. The normal prefix will indicate the presence of 3-12 carbons for the alkanes in Figure 4.4, so the names should be propane to dodecane. Those names have already been taken for the acyclic alkanes To distinguish between the linear 12-carbon molecule (dodecane) and the 12-membered cyclic (ring) alkane, use the term cyclo. If the ring is viewed as a cycle, then the prefix cyclo is used in front of the alkane name (a prefix in front of the carbon number prefix). The three-membered ring alkane therefore becomes cyclopropane and the 12-membered ring alkane becomes cyclododecane (see Figure 4.4). 

The nomenclature currently in use is based on conventions established in 1962 (4). Originally, all markers were designated with the prefix A, e.g., Ab4. The prefix is now often omitted when the locus has been established. Some investigators use the prefix As without specifying the locus, e.g., As4. The present authors feel that use of the locus designation conveys useful information to the reader, particularly since markers controlled by a given locus may not be numbered sequentially (e.g., b4, b5, b6, b9 c7, c21). 

The Stock Oxidation-Number System. Stock sought to correct many nomenclature difficulties by introducing Roman numerals in parentheses to indicate the state(s) of oxidation, eg, titanium(II) chloride for TiCl2, iron(II) oxide for FeO, titanium(III) chloride for TiCl, iron(III) oxide for Fe203, titanium(IV) chloride for TiCl, and iron(II,III) oxide for Fe O. In this system, only the termination -ate is used for anions, followed by Roman numerals in parentheses. Examples are potassium manganate(IV) for K2Mn02, potassium tetrachloroplatinate(II) for K PtCl, and sodium hexacyanoferrate(III) for Na3Fe(CN)3. Thus a set of prefixes and terminations becomes uimecessary. 

Ans. The three compounds belong to different nomenclature classes. Aluminum in its compounds always forms 3+ ions, and thus there is no need to state 3+ in the name. Cobalt forms 2+ and 33-ions, and we need to designate which of these exists in this compound. PCI, is a binary nonmctal-nonmetal compound, using a prefix to denote the number of chlorine atoms. 

Throughout this article, the heteroring will be referred to as either piperazine-2,5-dione or occasionally as cyclodipeptide. The earlier practice of referring to the ring as diketopiperazine has been avoided. The numbering of the piperazinedione ring is as shown in (1). In the cyclodipeptide nomenclature, the common three-letter code for the two amino acids, with the necessary prefix to indicate absolute configuration, will be used. 

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