The gas-phase reactions of Pt+ and Au+ with C2H4, C3H6, 1-C4H8, cis-2-C4H8, and trans-2−C4H8 have been carried out under thermal and near-thermal conditions using a SIFT reactor and a drift cell. In all reactions examined here, Pt+ exhibits dehydrogenation as the dominant primary product channel, but elimination of methane and ethene are observed in some systems in small amounts. Evidence for both allylic and vinylic activation of σ-bonds is observed. Observation of these bimolecular processes allow us to calculate D(Pt+· acetylene) > 49.76 ± 0.01 kcal/mol, D(Pt+·allene) > 40.75 ± 0.01 kcal/mol, D(Pt+·propyne) > 39.7 ± 0.1 kcal/mol and D(Pt+·butadiene) > 29.01 ± 0.01 kcal/mol. Hydride abstraction is also observed as a minor product channel in the reactions of Pt+ with C3H6 and all three butene isomers. Secondary and tertiary reactions in the Pt+ systems are limited to clustering reactions. Hydride abstraction is the only primary bimolecular pathway observed in the reactions of Au+ with propene as well as the butene isomers. Au+ forms adducts with both C2H4 and C3H6 in primary steps. Follow-on reactions are also observed in the Au+ systems which include both bimolecular and clustering steps. Ion mobility experiments carried out using the drift cell indicate that both Pt+ and Au+ are in their ground states in the reactions described here. However, we show evidence that an Au+ excited state can be populated under the appropriate ionizing conditions. Reduced zero-field mobilities for ground-state Pt+ and Au+ have been determined to be 20.6 ± 0.6 and 19.5 ± 0.5 cm2/V·s, respectively.