Presence Of Dienes Research Articles

Hydrogenation of isoprene and 2,3-dimethylbuta-1,3-diene on a skeletal cobalt catalyst

1. 1. Skeletal cobalt catalyst has a considerable activity and high selectivity of action in hydrogenation of isoprene and 2,3-dimethylbuta-1,3-diene. 2. 2. The α-olefins forming do not hydrogenate in the presence of dienes as a consequence of adsorption displacement. 3. 3. The cobalt catalyst, with a higher selectivity than that of a nickel catalyst, directs the hydrogenation of dienes into the 1,2- and 3,4-positions with the formation of thermodynamically less stable 2-methylbut-1-ene and 2,3-dimethylbut-1-ene. 4. 4. Cobalt catalyses the transfer of the double bond in isopentene and isohexene to a small extent.

Reaction of dialkyl(or aryl) dichlorosilanes with alkali metals in presence of conjugated dienes

The reaction of dialkyl(or aryl)dichlorosilanes with conjugated dienes in presence of alkali metals in a tetrahydrofuran medium leads to the formation of unsaturated sila-hydrocarbon polymers with silicon atoms in the main chain and molecular weights of 1000 or over, and also the corresponding silacyclopentenes (yields 0–10%) and divinylsilacyclopentanes (yields 10–50%). The relative amounts (yields) of these products depend both on the nature of the reactants and on the reaction conditions.