For the gas phase isomerization of isopropenyl allyl ether CH2 C(CH3)-O-CH2CH-CHCH3COCH2CH2CH-CH2 -1 the rate constant has been determined at several temperatures. When In k in s is plotted against the reciprocal of the Kelvin temperature, the resulting linear plot has a slope of-1.48x104 K and a y-intercept of 26.0. The activation energy for the gas phase isomerization of isopropenyl allyl ether is kJ/mol.