Catalytic hydrogenation of acetylenic

Hydrogenation. Acetylene can be hydrogenated to ethylene and ethane. The reduction of acetylene occurs in an ammoniacal solution of chromous chloride (20) or in a solution of chromous salts in H2SO4 (20). The selective catalytic hydrogenation of acetylene to ethylene, which proceeds... 

It has been proposed (Shankar, PhD Thesis, Monash University, Australia, 1976) that the gas phase catalytic hydrogenation of acetylene occurs by... 

Additions at the triple bond. The catalytic hydrogenation of acetylenes gives predominantly the cis isomer. The reason is obvious. Both the hydrogen atoms approach the double bond from the same side from the side of the catalyst. The hydrogenation of phenyl propiolic acid is an example. 

The researches of Zal kind were concerned with the catalytic hydrogenation of acetylenic compounds acetylenic glycols add only two hydrogen atoms over palladium and divinylacetylenes add only six hydrogen atoms, the hydrogenation being limited to the formation of olefins (431). 

Carbides of Rh, Ir and Pt have not been found to form. An unstable carbide forms with Pd during the catalytic hydrogenation of acetylene. ... 

This study focuses on the vapor-phase catalytic hydrogenation of acetylene to ethylene and ethane ... 

Since both complete hydrogenation of acetylene or any hydrogenation of the ethylene results in the production of a less valuable product such as ethane, conditions must be chosen carefiiUy and a catalyst must be used that is both sufficiently active for acetylene hydrogenation and extremely selective to avoid ethylene hydrogenation. Since hydrogenation of acetylenic bonds proceeds stepwise and since acetylene is more strongly adsorbed on the catalytic... 

The presence of other functional groups ia an acetylenic molecule frequendy does not affect partial hydrogenation because many groups such as olefins are less strongly adsorbed on the catalytic site. Supported palladium catalysts deactivated with lead (such as the Liadlar catalyst), sulfur, or quinoline have been used for hydrogenation of acetylenic compound to (predominantiy) cis-olefins. 

Conditions have been optimized for catalytic hydrogenation of the acetylene group of the vitamin A synthesis intermediate (110). Several chemical reactions of geometrical isomers of the product (111) and its acetate and of (110) have been described. " ... 

Sonogashira, K. Tohda, Y. Hagihara, N. A Convenient Synthesis of Acetylenes Catalytic Substitutions of Acetylenic Hydrogen with Bromoalkenes, Iodoarenes and Bromopyridines, Tetrahedron Lett. 1975, 50, 4467-4470. 

The acetylenic acetals are easily hydrolyzed to the corresponding aldehydes in high yields in the presence of dilute acids.3-4 Acetylenic acetals have also been of value in the synthesis of ,/3-unsatu rated ethylenic acetals or aldehydes by partial catalytic hydrogenation of the triple bond.4... 

One of the characteristics of many catalytic hydrogenation reactions is the ability of the catalyst to promote the formation of more than one reaction product. Thus, for example, in the hydrogenation of acetylene, ethylene may be formed as an intermediate in the production of ethane and may be the major product in the initial stages of the reaction... 

The hydrogenations of dialkylacetylenes are of particular interest from a stereochemical viewpoint since, as noted in Sect. 4.3, the adsorbed state of the acetylene is expected to adopt a c/s-configuration and, consequently, upon hydrogenation to yield the cis-olefin. Wide use of this fact has been made in preparative organic chemistry as noted by Burwell [192] and by Campbell and Campbell [193]. Although early studies of the catalytic hydrogenation of disubstituted acetylenes [194—196] revealed the formation of trans- as well as c/s-olefins, it was generally assumed that the trans-isomer was formed by isomerisation of the cis-ole-fin. However, more recent studies have shown that this view may have... 

In selective poisoning or selective inhibition, a poison retards the rate of one catalysed reaction more than that of another or it may retard only one of the reactions. For example, there are poisons which retard the hydrogenation of olefins much more than the hydrogenation of acetylenes or dienes. Also, traces of sulphur compounds appear selectively to inhibit hydro-genolysis of hydrocarbons during catalytic reforming. 

N. (1975) A convenient synthesis of acetylenes catalytic substitutions of acetylenic hydrogen with bromoalkenes, iodoarenes and bromopyridines. Tetrahedron Lett., 16, 4467. 

The combination of surface-associated reactants with surface-bound H-atoms, occasionally leads to poor photoinduced hydrogenation of the reactant and parallelly to inhibition of H2-evolution. For such systems, tailored bifunctional heterogeneous catalysts have been developed [141], where cooperative catalytic effects are observed in the photohydrogenation reactions. Substitution of ethylene by acetylene, C2H2, in the photosystem composed of Ru(bpy) +/MV2+/Na2EDTA and the Pt colloid results in inefficient hydrogenation of acetylene to ethylene,

[Pg.184]

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