To find out the conditions for mild hydration of carbon-carbon triple bonds the hydration reactions of some terminal alkynes (FcC CH, PhC CH, C5H11 C CH) on the Nafion film in supercritical carbon dioxide (sc-SO2) were studied. The corresponding ketones were prepared in excellent yields. The hydration of 1-heptyne is accompanied by the isomerization of the terminal carbon-carbon triple bond into the internal one under acidic heterogeneous catalysis. (C) 2013 Elsevier B.V. All rights reserved.