AbstractThe Wittig synthesis has been used to prepare conveniently carbon‐14 labeled 1‐olefins in the C5to C8range in about 60 % yield. The chemical and radiochemical purities of the products exceeded 99.5 %. The common source of carbon‐14 in these reactions was methyl‐14C‐triphenylphosphonium iodide which was readily and quantitatively prepared from commercially available methyl