1,4-Pentadiene oxidation with pinane and cumene hydroperoxides was examined. The application of crude cumene hydroperoxide was shown to yield 90% 1,2-epoxypentene-4 at an oxidant conversion of over 95%. The isomerization of 1,2-epoxypentene-4 in the vapor phase at 290-330 degreesC on lithium phosphate was studied. The rearrangement yielded 2,4-pentadiene-1-ol and unsaturated carbonyl compounds in a nearly 1 ratio at an epoxide conversion of 50%. Carbonyl compounds consisted mainly of pentenals with a different double-bond position. The results of the rearrangement show that the epoxide C-O bond heterolysis takes place mainly on the allyl group side. mainly on the allyl group side.