Nomenclature Roman numerals

In an attempt to be consistent with accepted chemistry nomenclature, Roman numeral superscripts to the right of element symbols (e.g. Biv) will frequently be used to indicate oxidation number and to emphasize that this number does not suggest any particular degree of ionization. This paper contains some discussion of the meaning of these superscripts. 

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. 

Many transition metals and the group of six elements centered around lead on the periodic table commonly have more than one valence. The valence of these metals in a compound must be known before the compound can be named. Modern nomenclature rules indicate the valence of one of these metals with a Roman numeral suffix (Stock notation). Older nomenclature rules used different suffixes to indicate the charge. Examples ... 

Several hundred restriction enzymes have been isolated and characterized. Nomenclature for the enzymes consists of a three-letter abbreviation representing the source (Eco — E. colt), a letter representing the strain (R), and a roman numeral designating the order of discovery. fcoRI is the first to be isolated from E. coli (strain R) and characterized. Table E15.1 lists several other restriction enzymes, their recognition sequence for cleavage, and optimum reaction conditions. 

The Stock Oxidation-Number System. Stock sought to correct many nomenclature difficulties by introducing Roman numerals in parentheses to indicate the s(ate(s) of oxidation. 

Nomenclature Restriction enzymes are isolated from bacteria, where they play a role in protecting the host cell against virus infection. Over 100 restriction enzymes have now been isolated and have been named according to the bacterial species from which they were isolated. The first three letters of the enzyme name are the first letter of the genus name and the first two letters of the species name. Since each bacterium may contain several different restriction enzymes, a roman numeral is also used to identify each enzyme. EcoRI, for example, was the first enzyme isolated from Escherichia cgli. 

This Roman numeral method is known as the Stock system. An older nomenclature used the suffix -ous for the lower charge and -ic for the higher charge and is still used occasionally. 

Naming ions of metals that form ions of more than one charge requires distinguishing between the possibilities. For example, iron forms Fe and Fe ions. We cannot call both of these iron ion because no one would know which of the two we meant. For monatomic cations of variable type, the charge in the form of a Roman numeral is attached to the element s name to indicate which ion we are talking about. For example, Fe is called iron(II) ion and Fe is called iron(lll) ion. This system of nomenclature is called the Stock system. 

Stock system (6.2, 16.2) The nomenclature system for inorganic compounds in which the oxidation state (or charge for a monatomic cation) is represented as a Roman numeral in the name of the compound, stoichiometry (10.1) The determination of how much a reactant can produce or how much of a product can be produced from a given quantity of another substance in a reaction. 

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. 

TABLE 19-7 Roman Numerical Nomenclature of Blood-Clotting Factors and Some Common Synonyms ... 

The practice of using Roman numerals has become widespread. Any change at this time would add still another nomenclature system to a field which is already confused by too many different systems. Consequently, there ought to be very convincing reasons for making any change. 

The oxidation number (see Sections IR-4.6.1 and IR-9.1.2.8) of an element is indicated by a Roman numeral placed in parentheses immediately following the name (modified by the ending ate if necessary) of the element to which it refers. The oxidation number may be positive, negative or zero (represented by the numeral 0). An oxidation number is always non-negative unless the minus sign is explicitly used (the positive sign is never used). Non-integral oxidation numbers are not used for nomenclature purposes. 

The exact chemical nature of EH2, i.e., the status of the two electrons shared between the FAD and the disulfide, has been much debated and perhaps cannot be adequately described by any single nomenclature. It has variously been referred to as a biradical (II) (24, 26, 28), as a charge transfer complex in which thiolate is the donor and FAD the acceptor (III) (28, 56, 56a), and as a covalent bond between FAD and sulfur (IV) (57). The roman numerals refer to the structures below in which only... 

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