The Catalytic Isomerization of Butene-1

It has been shown that butene-1 undergoes isomerization to butene-2 on a nickel catalyst in the presence of hydrogen. By using deuterium, this double-bond migration has been examined simultaneously with the exchange and hydrogenation reactions. The kinetics of double-bond migration and hydrogenation at 65$^{\circ} $C were found to be identical, the rate of reaction in both cases being proportional to the square root of the butene pressure and to the square root of the hydrogen pressure. Energies of activation for the three reactions were measured over the temperature range 76-126$^{\circ} $C and the following values found: Exchange 9$\cdot $0 kcal. Hydrogenation 2$\cdot $5 kcal. Double-bond migration 5$\cdot $9 kcal. At the lowest temperatures, the rate of double-bond migration was about six times that of exchange. These facts are in agreement with the theory that the catalytic exchange between olefines and deuterium takes place through the formation of an associative complex. The rate-determining step in the double-bond migration is the second, fast step of the exchange reaction, viz. $ \matrix\format\l \\ \text{CH}_{2} \chembond{1,0} \text{CH} \chembond{1,0} \text{CH}_{2} \chembond{1,0} \text{CH}_{3}\quad \text{D}\quad \quad \text{CH}_{2}\text{D} \chembond{1,0} \text{CH} \chembond{1,0} \text{CH}_{2} \chembond{1,0} \text{CH}_{3}\quad \quad \text{CH}_{2}\text{D} \chembond{1,0} \text{CH} \chembond{1,0} \text{CH} \chembond{1,0} \text{CH}_{3}\quad \text{H} \\ \ \Big|\quad \quad \ \ \Big|\quad \quad \quad \quad \quad \quad \ \ \ +\Big|\quad \rightleftarrows \quad \quad \quad \quad \Big|\quad \quad \ \ \quad \quad \quad \quad \quad \rightleftarrows \quad \ \quad \quad \quad \Big|\quad \quad \ \Big|\quad \quad \quad \quad +\Big| \\ \text{Ni}\quad \quad \text{Ni}\quad \quad \quad \quad \quad \quad \quad \ \ \text{Ni}\ \quad \quad \quad \quad \quad \ \,\text{Ni}\quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \ \ \text{Ni}\ \,\quad \text{Ni}\quad \quad \quad \ \,\quad \text{Ni} \\ \ \quad \quad \quad \quad \quad \quad \text{Butene-}1\quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \quad \text{Butene-}2 \endmatrix $