Some catalysts, especially at high temperatures, are known to produce radical species into the gas phase, generating a complex heterogeneous-homogeneous reaction network. Such reactions are prevalent for catalytic combustion reactions of hydrocarbons, but it is interesting if partial oxidation products are targeted as a consequence of such radical chemistries. This contribution discusses our recent progress on selective catalytic generation of OH radicals from H2O and O2 mixture, which is utilized for hydrocarbon transformations, such as methane coupling and ethane dehydrogenation. Alkali metal catalysts (mainly Na), often at a molten state under reaction condition, are active for the selective generation of OH radical through a quasi-equilibrated formation of peroxide species, without activating hydrocarbons significantly on the surface. This OH radical reaction path makes it silent for competitive adsorption of hydrocarbons and their derivative products, beneficial to improve selectivities, such as CH4 vs. C2H4. Gas phase reaction selectivity generally reflects the C-H bond strengths of the hydrocarbons to abstract H from them and it enables to predict the targeted product selectivity and yield. As a consequence, ~30% carbon yield from CH4 to C2 was achieved using Na2WO4/SiO2 catalyst at ~850-900 °C. A perspective to produce other hydrocarbons via OH radical pathways is also discussed.