In the gas phase at about 500° allyl ethers undergo decomposition through a cyclic, six-atom transition state with transfer of a hydrogen atom to give high yields of a carbonyl compound and a propene, in which the double bond has moved from the 2,3- to the 1,2-position of the allyl system. The rate of reaction is rather insensitive to structural variation in either the allyl or alkyl part of the ether. Allyl α-deuterodiphenylmethyl ether reacts only about 10% slower than the undeuterated compound.