Page 73 - Nomenclature of Inorganic Chemistry (IUPAC Recommendations 2005)

F O R M U L A E IR-4.5

IR-4.5 I S O T O P I C A L L Y M O D I F I E D C O M P O U N D S

IR-4.5.1 General formalism
The mass number of any specific nuclide can be indicated in the usual way with a l eft
superscript preceding the appropriate atomic symbol (see Section IR-3.2).
When it is necessary to cite different nuclides at the same position in a f ormula, the
nuclide symbols are written i n a lphabetical order; when their atomic s ymbols are
identical the order is that of increasing mass number. Isotopically modified compounds
may be classified as isotopically substituted compounds a nd isotopically labelled
compounds.

IR-4.5.2 Isotopically substituted compounds
An isotopically substituted compound has a c omposition such that all the molecules of the
compound have only the indicated nuclide(s) at each designated position. The s ubstituted
nuclides a re indicated by insertion of the mass n umbers as left superscripts p receding the
appropriate atom symbols in the normal formula.

Examples:

3
1. H HO
36
2. H Cl
3. 235 UF 6
14
4. 42 KNa CO 3
5. 32 PCl 3
32
6. K[ PF 6 ]
42
14
7. K 3 K[Fe( CN) 6 ]

IR-4.5.3 Isotopically labelled compounds

IR-4.5.3.1 Types of labelling

An isotopically labelled compound may be considered formally a s a mixture of an
isotopically unmodified compound and one or more analogous isotopically substituted
compounds. They may be divided into several different types. Specifically labelled
compounds and selectively labelled compounds are treated briefly here and described in
more detail in Ref. 5.

IR-4.5.3.2 Specifically labelled compounds

An isotopically labelled compound is called a s pecifically labelled compound when a
unique i sotopically s ubstituted compound is added formally to the analogous
isotopically unmodified c ompound. A s pecifically labelled compound is indicated by
enclosing the appropriate nuclide symbol(s) and multiplying subscript (if any) in square
brackets.

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