Search results
Results from the WOW.Com Content Network
The hydrogenation of alkynes is troublesome to control since alkynes tend to be reduced to alkanes, via intermediacy of the cis-alkene. [14] Ethylene reacts with Wilkinson's catalyst to give RhCl(C 2 H 4)(PPh 3) 2, but it is not a substrate for hydrogenation. [10]
However, the reaction rate for most hydrogenation reactions is negligible in the absence of catalysts. The mechanism of metal-catalyzed hydrogenation of alkenes and alkynes has been extensively studied. [20] First of all isotope labeling using deuterium confirms the regiochemistry of the addition:
Crabtree's catalyst is an organoiridium compound with the formula [C 8 H 12 IrP(C 6 H 11) 3 C 5 H 5 N]PF 6. It is a homogeneous catalyst for hydrogenation and hydrogen-transfer reactions, developed by Robert H. Crabtree. This air stable orange solid is commercially available and known for its directed hydrogenation to give trans ...
The catalyst is used for the hydrogenation of alkynes to alkenes (i.e. without further reduction into alkanes). The lead serves to deactivate the palladium sites, and further deactivation of the catalyst with quinoline or 3,6-dithia-1,8-octanediol enhances its selectivity, preventing formation of alkanes. Thus if a compound contains a double ...
In chemistry, homogeneous catalysis is catalysis where the catalyst is in same phase as reactants, principally by a soluble catalyst in a solution. In contrast, heterogeneous catalysis describes processes where the catalysts and substrate are in distinct phases, typically solid and gas, respectively. [1]
Wilkinson's catalyst, RhCl(PPh 3) 3 is a square planar Rh(I) complex of historical significance used to catalyze the hydrogenation of alkenes. Vaska's complex , trans -IrCl(CO)(PPh 3 ) 2 , is also historically significant; it was used to establish the scope of oxidative addition reactions.
Idealized mechanism for metal-catalysed hydrosilylation of an alkene. Hydrosilylation of alkenes represents a commercially important method for preparing organosilicon compounds. The process is mechanistically similar to the hydrogenation of alkenes. In fact, similar catalysts are sometimes employed for the two catalytic processes.
A high catalytic activity, coupled with the fact that hydrogen is absorbed within the pores of the catalyst during activation, makes Raney nickel a useful catalyst for many hydrogenation reactions. Its structural and thermal stability (i.e., it does not decompose at high temperatures) allows its use under a wide range of reaction conditions.