Isotopologue

Not to be confused with isotopomers.

Isotopologues are molecules that differ only in their isotopic composition. Simply, the isotopologue of a chemical species has at least one atom with a different number of neutrons than the parent.

An example is water, where some of its hydrogen-related isotopologues are: "light water" (HOH or H₂O), "semi-heavy water" with the deuterium isotope in equal proportion to protium (HDO or ¹H²HO), "heavy water" with two deuterium isotopes of hydrogen per molecule (D₂O or ²H₂O), and "super-heavy water" or tritiated water (T₂O or ³H₂O), where the hydrogen atoms are replaced with tritium isotopes. Oxygen-related isotopologues of water include the commonly available form of heavy-oxygen water (H₂¹⁸O) and the more difficult to separate version with the ¹⁷O isotope. Both elements may be replaced by isotopes, for example in the doubly labeled water isotopologue D₂¹⁸O.

References

IUPAC, Compendium of Chemical Terminology, 2nd ed. (the "Gold Book") (1997). Online corrected version:  (1994) "Isotopologue".

See also

• Mass (mass spectrometry)

External links

• Fractional abundance of atmospheric isotopologues, SpectralCalc.com