Isotopically labelled compounds formulae

Isotopically Labeled Compounds. The hydrogen isotopes are given special names H (protium), H or D (deuterium), and H or T (tritium). The superscript designation is preferred because D and T disturb the alphabetical ordering in formulas. 

An isotopically labeled compound is a mixture of an isotopically unmodified compound with an analogous isotopically substituted compound or compounds. Isotopically labeled compounds may be specifically labeled or selectively labeled. To indicate isotopic labeling, the number and symbol (and locants if needed) are enclosed in square brackets closed up to the compound name or formula. 

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. 

The labeling of organic compounds with stable or radioactive isotopes now constitutes an extremely important area of preparative chemistry. The number of publications in that field has grown to such an extent that it is almost impossible to find them all. This alone indicates the ever growing importance of labeled compounds in diverse branches of science moreover, the work reactivates the experimental demands on preparative chemists because an extraordinarily large number of compounds of different isotopic composition are open to synthesis. For instance, even such a relatively simple molecule as propane can afford no less than twenty-nine different deuterium-labeled compounds with eight different molecular formulae. 

In biological and clinical investigations the position is somewhat different. In both instances the enrichments measured are often large and it is normal practice to express the enrichment of a particular fraction as compared to the same fraction prior to the introduction of the labelled compound to the system. In such cases most workers express enrichment of isotopic content as either atom% or atom% excess which have been defined earlier (p. 5). Where is used at low enrichments and measured in an isotopic ratio instrument normally equipped to monitor the m/e 28 and m/e 29 ion beams, the following formula is applicable ... 

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