Formulae isotopically modified compounds

For the use of atomic symbols to indicate isotopic modification in chemical formulae and the nomenclature of isotopically modified compounds see Section IR-4.5 and Chapter II-2 of Ref. 4 respectively. 

IR-4.4.3.2 Formal treatment as coordination compounds IR-4.4.3.3 Chain compounds IR-4.4.3.4 Generalized salt formulae IR-4.4.3.5 (Formal) addition compounds IR-4.4.4 Figand abbreviations IR-4.5 Isotopically modified compounds IR-4.5.1 General formalism IR-4.5.2 Isotopically substituted compounds IR-4.5.3 Isotopically labelled compounds IR-4.5.3.1 Types of labelling IR-4.5.3.2 Specihcally labelled compounds IR-4.5.3.3 Selectively labelled compounds IR-4.6 Optional modibers of formulae IR-4.6.1 Oxidation state IR-4.6.2 Formulae of radicals IR-4.6.3 Formulae of optically active compounds IR-4.6.4 Indication of excited states IR-4.6.5 Structural descriptors IR-4.7 References... 

IR-4.5.1 General formalism The mass number of any specific nuclide can be indicated in the usual way with a left 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 formula, the nuclide symbols are written in alphabetical order when their atomic symbols are identical the order is that of increasing mass number. Isotopically modified compounds may be classified as isotopically substituted compounds and isotopically labelled compounds. 

Table 19. Formulae and names of isotopically modified compounds in direct comparison...

In the modified Hill system as used by Chemical Abstracts today the arrangement of symbols in formulas is alphabetic, except that in carbon compounds C always comes first, followed immediately by H if hydrogen is also present. For deuterium and tritium compounds, D and T, respectively, are used. These are placed alphabetically in formulas the exception in arrangement made for H is not extended to include these isotopes, Glutamic-d acid is therefore written C5H8DNO4, The names of certain elements and their respective symbols are given preference over former names. The preferred names are astatine, beryllium, niobium, hafnium, and promethium (but not wolfram) (7). 

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