Reppe synthesis

The main uses of metal carbonyls are in the areas of catalysis and organic synthesis. The Reppe synthesis and 0x0 process are both of enormous industrial importance. 

Figure 4.37 Synthesis trees for Reppe synthesis of cyclooctatetraene (a) treating each molecule of acetylene as a separate input (b) treating all 4 acetylene molecules as a single input.

The hydroformylation reaction has been the subject of excellent reviews (for example I, 6-8) therefore, the object of this particular treatise is not to provide comprehensive coverage of all aspects. The basic chemistry is presented, along with recent developments of interest as reported in the literature, although not in chronological order. Stereochemical studies (6) are included only when pertinent to another point under consideration. Carbonylations or hydrocarboxylation reactions which produce ketones, esters, acids, esters, or amides are not included (/). Also not included is the so-called Reppe" synthesis, which is represented by Eq. (1). 

Acetylene industry in wartime Germany) 6a)W.Reppe, "Advances in Acetylene Chemistry (as developed at the IG Farbenindustrie A-G), PB Rept 1112(CWS IDR No 4l49)(about 1946) 6b)W.Reppe, "Synthesis of Intermediates for Polyamids on Acetylene Basis," PB Rept 25553(about 1946) 7)V. Brameld M.Clark, JSCI 65,... 

We have restricted ourselves to discussing stoichiometric and catalytic reactions which clearly involve 7r-allylnickel complexes and have not considered polymerization reactions, the Reppe synthesis, or template reactions. Fortunately there is an abundance of books and reviews which cover these fields as well as the similarities, and dissimilarities, with the other transition metals (1-8). The literature up to the end of 1968 has been surveyed but no attempt has been made to include all the material available. 

Acrolein and condensable by-products, mainly acrylic acid plus some acetic acid and acetaldehyde, are separated from nitrogen and carbon oxides in a water absorber. However in most industrial plants the product is not isolated for sale, but instead the acrolein-rich effluent is transferred to a second-stage reactor for oxidation to acrylic acid. In fact the volume of acrylic acid production ca. 4.2 Mt/a worldwide) is an order of magnitude larger than that of commercial acrolein. The propylene oxidation has supplanted earlier acrylic acid processes based on other feedstocks, such as the Reppe synthesis from acetylene, the ketene process from acetic acid and formaldehyde, or the hydrolysis of acrylonitrile or of ethylene cyanohydrin (from ethylene oxide). In addition to the (preferred) stepwise process, via acrolein (Equation 30), a... 

The only industrial application, the synthesis of butanol from propene (Reppe synthesis), was not very successful (297). This reaction is catalyzed by iron carbonyls in the presence of tertiary ammonium salts the trinu-clear cluster anion [HFe3(CO) ] detected in the reaction mixture has been discussed as the active species (298). Spectroscopic studies under CO pressure, however, showed the trinuclear anion [HFe3(CO) ]- to be converted into the mononuclear species [HFe(CO)4] (299), and this anion is now assumed to be the catalyst in the Reppe reaction (290). 

If hydrogen is replaced by steam, a mixture of primary butanols can be obtained directly. This is the BASF process (Reppe synthesis) with one unit operating in Japan. It produces an effluent containing 88 per cent n-butanol and 12 per cent isobutanol. The main reaction involved is the following ... 

Fatty acids (mostly branched) are produced from alkenes by addition of water and carbon monoxide (Reppe synthesis) or addition of hydrogen and carbon monoxide (Roelen or Oxo reaction) with subsequent oxidation (24,25). However, our studies with added alkenes (e.g., Figure 5) indicated that the olefins produced were not precursors of either the normal or branched fatty acids. Oxygenated compounds, such as normal... 

The Reppe synthesis, shown in reaction (5.59), has a formal resemblance to hydroformylation, with Hj replaced by H2O. 

Acrylic ester synthesis from acetylene, carbon monoxide, and alcohols with the aid of nickel carbonyl is known as the Reppe synthesis and is very important in industrial applications (Reppe, 1953). This carboxylation re-... 

---