Enclosing marks 336

Chemical nomenclature employs three types of enclosing mark, namely braces, square 

In formulae, these enclosing marks are used in the following nesting order [],[()],[ () ], [( () )], [ ( () ) ], etc. Square brackets are normally used only to enclose entire formulae parentheses and braces are then used alternately (see also Sections IR-4.2.3 and IR-9.2.3.2). There are, however, some specific uses of square brackets in formulae, cf. Section IR-2.2.2.1. 

In names, the nesting order is ( ), [( )], [( )], ( [( )] ), etc. This ordering is that used in substitutive nomenclature, see Section P-16.4 of Ref. 1. (See also Section IR-9.2.2.3 for the use of enclosing marks with ligand names.) 

Square brackets are used in formulae in the following ways. 

No numerical subscript should follow the square bracket used in this context. For example, where the molecular formula is double the empirical formula, this should be indicated inside the square bracket. 

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Enclosing Marks. Where it is necessary in an inorganic formula, enclosing marks (parentheses, braces, and brackets) are nested within square brackets as follows ... 

Neutral and Cationic Ligands. Neutral and cationic ligands are used without change in name and are set off with enclosing marks. Water and ammonia, as neutral ligands, are called aqua and ammine, respectively. The groups NO and CO, when linked directly to a metal atom, are called nitrosyl and carbonyl, respectively. 

The dashes at each end of the formulae of entries 1, 2, 3, 4, 7, and 8 are drawn fully inside the enclosing marks, because the identities of the units at the ends of the chains are unknown. 

The name of the polymer is simply the name of the preferred CRU enclosed in curves, square brackets or braces and prefixed by poly. The nesting order of enclosing marks is curves, square brackets, braces, then curves, square brackets, braces, etc., i-6- [( [( )] )] This is well illustrated in Examples 21 and 31 in Section 9. 

Rule 1.4 Side-groups or substituents written on the same line as the backbone of the macromolecule and consisting of more than one atom symbol are set between enclosing marks, usually parentheses. 

Rule 1.5 Enclosing marks together with subscript letters denote multiplicity of the enclosed constitutional units. The enclosing marks are parentheses (round brackets) or (square) brackets and can be used at random, except for inorganic polymers, for which exclusive use of parentheses is recommended for this purpose, in order to avoid confusion with (square) brackets, which denote coordination structures. 

Rule 1.7 The formulae of end groups, if known, may be attached to the bonds at the ends of the constitutional units, but placed outside the enclosing marks. 

Note The chemical bonds connecting the constitutional repeating units are represented by dashes drawn across the enclosing marks. 

Note 2 The bonds emanating from the first and last constitutional or junction unit of an irregular block are written within the enclosing marks when it is not known to which of the units of the irregular block the other blocks or the end groups of the polymer are attached. Thus,... 

Where it is known that certain atoms in a molecular ion are bound together to form a group, as with S and O in S04 , these elements can be so grouped in the formula, with or without enclosing marks, depending upon the compound and upon the users requirements. 

Organic ligands are cited under C, and NO and CO are regarded as neutral. Because square brackets are always of highest seniority (or priority), a hierarchical sequence of enclosing marks is adopted to ensure that this seniority is preserved [ ], [()], [ () ], [ [()] ], [ [()] ], etc. 

Note that upon forming a full name — as in Na4Sn9, tetrasodium (nonastannide) and Tl(l3), thallium (triiodide) — enclosing marks may be useful to avoid ambiguity. Compare with TII3, thallium triiodide. In some circumstances, such as when the name of the electronegative species is cited alone, e.g. in the discussion of an anion, it may be useful to indicate the charge Sn9 , nonastannide(4-) (13) , triiodide(l-) 82 , disulfide(2-). This is discussed further below. Some trivial names are still... 

Of the two kinds of numerical prefix (see Table 4.2), the simple di-, tri-, tetra-, etc. are generally recommended. The prefixes bis-, tris-, tetrakis-, etc. are to be used only with more complex expressions and to avoid ambiguity. They normally require parentheses around the name they qualify. The nesting order of enclosing marks is as cited on p. 13. There is normally no elision in instances such as tetraammine and the two adjacent letters a are pronounced separately. 

Coordination compounds. [In the formula of a coordination entity.] the symbol of the central atom(s) is placed first, followed by the ionic and then the neutru] ligands. Square brackets are used to enclose the whole coordination entity whether charged or not. This practice need not be used for simple species such us the common oxoanions (NO, NOT, SO -, OH-, etc.). Enclosing marks are nested within the square brackets as follows [()]. U<) , [()]>]. [( [()] ]]. etc. 

When polyatomic cations and/or anions are involved, enclosing marks should be used to avoid possible ambiguity. Thus Tl lj is thallium (triiodide) and Tl11113 is thallium tn-ioJide. Alternatively. thalliumU) triiodide and thalliumfllh triiudide would suffice. 

For ranges in scientific notation, retain all parts of all numbers or avoid ambiguity by use of parentheses or other enclosing marks. 

Use a space for simple multiplication of functions of the type/(x) (one-dimensional) or g(y, z) (multidimensional). Close up multipliers to such functions where applicable. You may also use additional enclosing marks instead of spaces. 

V Use enclosing marks (parentheses, brackets, and braces, also called fences) in accordance with the rules of mathematics. Enclose parentheses within square brackets, and square brackets within braces [()]. ... 

Use enclosing marks around arguments when necessary for clarity. sin(x + 1) sm[27i(x-y)/n]... 

The terms ea and exp a have the same meaning and can be interchanged. When an exponent to the base e is very long or complicated, replace the e with exp and place the exponent on line and in enclosing marks. Leave no space between exp and the opening enclosing mark. 

In running text, do not use the radical sign (V ) with long terms. Use enclosing marks around the term and a superscript 1/2,1/3,1/4 (etc.) for square, cube, fourth root (etc.), respectively. 

Use enclosing marks in accordance with the rules of mathematics. If the slash (/) is used in division and if there is any doubt where the numerator ends or where the denominator starts, use enclosing marks for one or the other or both. 

When an equation is too long to fit on one line, break it after an operator that is not within an enclosing mark (parentheses, brackets, or braces) or break it between sets of enclosing marks. Do not break equations after integral, product, and summation signs after trigonometric and other functions set in roman type or before derivatives. 

Multiplying affixes are integral parts of the chemical name they are set in roman type and are always closed up to the rest of the name (without hyphens). Use hyphens only to set off intervening locants or descriptors. Use enclosing marks (parentheses, brackets, or braces) to ensure clarity or to observe other recommended nomenclature conventions. Multiplying prefixes include the following ... 

Define nonstandard abbreviations in table footnotes. Name the variable being measured, and indicate the unit of measure after a comma or slash or within enclosing marks. Use the same style within and among all tables. 

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