Acetylenes and Their Derivatives in the Presence of Water

The catalytic carbonylation of acetylenes or their derivatives with carbon monoxide and water yields unsaturated carboxylic acids or their derivatives. Thus, acetylene reacts with carbon monoxide and water to give 

Metal Carbonyl Catalyzed Carbonylation Reppe Reactions 

Contrary to the hydroformylation or carbonylation of olefins, in the carbonylation of acetylenes addition of the carboxyl group occurs, without exception, to one of the C-atoms of the triple bond. Generally, isomerization of the unsaturated bond via intermediate metalorganic complexes or isomerization of the carbon skeleton are not observed. 

As mentioned above, the carbonylation of acetylenes may also be effected without pressure with stoichiometric amounts of Ni(CO)4 as CO donor in the presence of aqueous acids. After reaction of the carbon monoxide which was complexed with nickel, the remaining nickel is found as the salt of the acid present. 

As already stated by Reppe and later confirmed by Ohashi [421-423], the hydrogen resulting from the overall equation could never be found. It is apparently consumed through hydrogenation either of acrylic acid to propionic acid or of acetylene to ethylene or ethane. 

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