SummaryThe utility of Raman spectroscopy for noninvasive, real-time monitoring of a range of tritium gas labeling reactions has been investigated, using deuterium gas as a model in most cases. Reaction types include organoiridium-catalyzed heteroatom-directed exchange (HDE), olefin hydrogenation and catalytic aryl dehalogenation. Five examples of HDE reactions with several different substrate types were monitored by observation of Raman vibrational bands sensitive to the isotopic substitutions. Changes in peak intensities and/or frequencies associated with the course of labeling are clearly observable at concentrations and reaction scales typical of tritium gas reactions. Similarly, Raman bands sensitive to the chemical changes that occur during catalytic deuterogenation of an olefin and to catalytic deuterium-bromine exchange of an aryl bromide were successfully monitored. This methodology can provide unprecedented real-time information, otherwise difficult to obtain, over the course of such reactions.