The protioformylation of (E)-1,1,1-2H3-2-butene and the deuterioformylation of (E)-2-butene have been carried out using Co2(CO)8, Rh4(CO)12 or Pt(SnCl3)Cl{(R, R)-Diop} as the catalyst precursor. The formation of the straight chain aldehyde, which implies hydrogen abstraction from a saturated methyl group, shows a positive isotope effect for the rhodium (~3 at 100 °C) and for the platinum (~2.1 at 80 °C) but none for the cobalt catalytic system. In the reactions catalyzed by Co2(CO)8, essentially no scrambling of the label takes place with the gas phase. The addition-elimination reaction of the metal hydride to the olefinic substrate is more rapid for the cobalt catalyst than for the other two systems, but does not imply olefin dissociation. © 1990.