Optimization, mechanism, and kinetics of the hydrogenation of skipped polyynoic acids to all‐cis skipped polyenoic acids

Hydrogenation of skipped polyynoic acids and esters over Lindlar's catalyst in the presence of quinoline proceeds with optimum results in light petroleum, ethyl acetate, or acetone at room temperature, yielding the corresponding all‐cis polyenoic compounds in purities of 90‐99%, depending on the number of triple bonds. For hydrogenations of this type mechanistic schemes are presented, including the formation of ene‐ynoic intermediates. Using Langmuir adsorption and Hinshelwood kinetics, analogue computer simulation showed a simultaneous uptake of more than one H2 molecule to be an important step in the reaction route. The formation of trans‐double bonds occurs only via isomerization of cis‐double bonds.