ABSTRACT
The fundamental basis of chemistry is not the chemical element itself, but more precisely, the isotope. So that precise information on the intimate origin of a chemical compound consists not only of a perfect description of the whole and global population of molecules but more accurately of a scrupulous sorting of the various isotopomers which constitute this population. Starting from raw materials with various isotopic compositions and undergoing various isotope effects all along the synthetic or biosynthetic pathways, molecules progressively acquire a characteristic isotopic composition that constitutes their own “isotopic signature”. It is obvious that a complete and meticulous sorting of each isotopomer would be quite unrealistic, but the measurement of isotope ratios of each of its constituting elements can act as the specific isotopic signature. Table 1 gathers the natural stable isotopes of interest in organic chemistry and their natural abundance. This isotopic signature can be self-generated during synthetic processes without any intentional modification. This signature can also be intentionally produced by adding precursors artificially enriched with stable isotopes in the reactional medium where the synthesis or biosynthesis takes place. Therefore, this intentionally modified isotope composition can be considered as an isotopic signature of the commercial or industrial property of the compound. List of Stable Isotopes of Hydrogen, Carbon, Nitrogen, Oxygen, and Sulfur, with their Atomic Weights and Natural Relative Abundances (%)
Element
Atomic weight
Natural relative abundance (%)
1H
1.0078
99.985
2H
2.0141
0.015
12C
12
98.89
13C
13.003
1.11
14N
14.003
99.63
15N
15.000
0.37
16O
15.994
99.759
17O
16.999
0.037
18O
17.999
0.204
32S
31.972
95.05
34S
33.967
4.22
