Isotopic modifiers

Reduction of aldonolactones and their derivatives with isotopically modified reducing agents leads to sugars labeled at the anomeric center. Glycosides substituted with deuterium or labeled with tritium are widely employed for kinetic isotope-effect measurements, mechanistic studies, isotope-tracing experiments, and so on. 

A similar reaction using the [2,2,4,4-2Hj isotopically modified compound in refluxing diglyme gave the corresponding isotopically modified product in 22% yield.16... 

Section H Isotopically Modified Compounds http //www.chem.qinul.ac.uk/iupac /se ctionH/... 

An isotopically unmodified compound is one whose isotopic nuclides are present in the proportions that occur in nature. An isotopically modified compound has a nuclide composition that deviates measurably from that occurring in nature. 

There are two main methods used for naming isotopically labelled compounds. For specifically labelled compounds, lUPAC recommends forming the name by placing the nuclide symbols (plus locants if necessary) in square brackets before the name of the unlabelled compounds or that part of the name which is isotopically modified. 

We have recently reported the discovery of four strong lines in the infrared and three broader features in the near ultraviolet, observed in absorption spectra of laboratory-produced carbon smoke [9]. The infrared lines have also been noticed by other investigators [10], The aim of this communication is to report new spectroscopic results on isotopically modified samples which support the idea that the reported features in fact originate from a pure and massive carbon molecule which very likely is the soccer-ball-shaped Cm molecule. 

Isotopically Modified Compounds, W.C. Fernelius, T.D. Coyle and W.H. Powell, Pure Appl. Chem., 53, 1887-1900 (1981). 

In isotopically modified compounds, a principle governs the order of citation of nuclide symbols. (See Section II-2.2.5 of Ref. 2.)... 

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. 

Nogi, N., T. Noda, and S. Tanaka. 2000. Phonon properties of isotopically modified 3-rhombohedral boron. J. Solid State Chem. 154 296-300. 

Note that the subscript x is used to denote material of natural isotopic abundance and the subscript y is used to denote isotopically modified material. 

The application of isotopes in science, in general, and in analytical chemistry, in particulate is based on two rather contradictory suppositions. Tracer experiments demand the same or very similar behavior of the isotopically modified and unmodified compounds. The study of the effects of isotopes requires the recognition, measurement, and interpretation of minute differences in the chemical and physical properties of compounds that differ only in their isotopic composition (isotopomers). These differences produce a different behavior of the isotopomers in all types of chromatographic processes, and these isotope effects have been demonstrated experimentally. 

Only the isotope-modified compound Is specified in the table. 

The preparation of a specific isotope, of an isotopically modified (i.e., mixture of labeled and unlabeled), isotopically substituted, or even site-specifically labeled compound is often mandatory in analytical applications. 

Each component of the mixture is assumed to be a molecular substance (nonelectrolyte), organic (i.e. containing carbon) or inorganic. Each substance has a well-defined relative molar mass corresponding to die natural isotopic abundances of the constitutive elements. Substances containing isotopically modified atoms are clearly identified in the tables which follow (Chap. 2). 

The fundamental vibrational bands (vj ) of small polyatomic molecules are often disturbed by the presence of hot bands (often of the type Vi + Vj Vj - see figure 7) and also by the corresponding fundamental bands of isotopically modified molecules (which are present in my sample in natural abundance). The most important isotopes in this respect are Cl/ Cl, Br/ Br ( H... 

If needed, isotopic modifiers (Section 6.6) and stereochemical descriptors (Section 6.7) must be added. 

Since the lUPAC nomenclature system relies totally on the pivotal concept of the parent structure to which, in a second sphere, substituents are assigned, it appeared advisable to maintain this division also for the chapters of this book. Thus, we begin with the exposition of the nomenclature rules for parent structures and, in the second chapter, proceed with the discussion of the different types of nomenclature for substituted systems, radicals, and ions in the third chapter specific classes of functional compounds are addressed, followed, in the forth chapter, by the treatment of metal organyls and, in the fifth, of carbohydrates. The concluding sixth chapter takes up once again the construction of the final names of complex compounds including isotopic modifiers and stereochemical descriptors. 

Compounds having a nuclide composition deviating from that occurring in nature are defined as isotopically modified. The non-natural nuclides most important for organic chemistry are p,... 

All together five types of isotopically modified compounds can be differentiated, one for isotopically substituted (a) and four for isotopically labelled species (b-e). 

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

---