Isomers having the same number of each isotopic atom but differing in their positions. The term is a contraction of "isotopic isomer".
Isotopomers can be either constitutional isomers (e.g. CH2DCH=O and CH3CD=O) or isotopic stereoisomers (e.g. (R)- and (S)-CH3CHDOH or (Z)- and (E)-CH3CH=CHD). IUPAC STEREOCHEMICAL TERMINOLOGY (1993).
