REPPE Acetylene reaction

REIMER TIEMANN Phenolformylation 314 REISSERT - GROSHEINTZ FISCHER Cyanoamme reaction 315 REPPE Acetylene reaction 316 von RICHTER Aromatic earboxylation 317 von RICHTER - WIDMAN - STOERMER Cmnotme synthesis 318 RILEY Selenium dioxide oxidation 319 Rimnt 4... 

The following series of reactions illustrates the manufacture of the principal Reppe acetylene chemicals. 

Reppe has shown that secondary amines of low basicity, such as carbazole, diphenylamine, indole, imidazole, and benzimidazole, and amides such as pyrrolidone react with acetylene in the presence of strong alkali to give vinyl derivatives [81, 83, 84a, b] (Eq. 30). As described by Reppe, these reactions are... 

The syntheses of carboxylic acids and esters are widely studied processes. Since the first examples of carboxylation in the presence of metal carbonyls were reported by Reppe, these reactions are sometimes referred to as the Reppe reactions. In his pioneering work125-127 stoichiometric or catalytic amounts of [Ni(CO)4] and ethylene or acetylene were reacted in the presence of water or alcohols to form saturated and unsaturated acids and esters. Commercial processes are practiced in the manufacture of propionic acid, acrylic acid and acrylates (see Section 7.2.4). 

Cuprous Acetylide Catalysts. CuaC, supported on silica gel, kieselgubr etc can be used as a catalyst in some org reactions Refs l)W.Reppe, Acetylene Chemistry, ... 

Polymerization and Cyclization of Alkynes (163). In 1940 Reppe and Schweckendieck 163) discovered that the substitution derivatives of tetracarbonylnickel with phosphines, and particularly those of the type Ni(CO)2(PR3)2, catalyze the linear polymerization and the cyclization to benzene derivatives of alkynes. Schrauzer 167) more recently showed that stoichiometric amounts of bisacrylonitrilenickel give the cyclization reaction. The reaction becomes, on the contrary, catalytic in the presence of a tertiary phosphine. Meriwether and co-workers (57, 136, 137, I40) studied the possible mechanism of Reppe s reaction. They showed that both the polymerization and the cyclization reactions are particularly effective with monosubstituted acetylenes, and that the cyclization reaction is infiuenced by steric and electronic effects. They then proposed a mechanism by which the induction time is ascribed to this rather slow reaction ... 

J. W. Copenhaver, M. H. Bigelow, Acetylene and Carbon Monoxide Chemistry (New York, 1949) p 246 W. Reppe, Acetylene Chemistry, U.S. Dept. Commerce PB 18852-S (1949) Neue Entwicklungen auf dem Gebiet des Acetylens und Kohlenoxyds (Berlin 1949) H. Kroper, Houben-Weyl 4/II, 413-422 (1955) D. W. F. Hardie, Acetylene, Manufacture and Uses (New York, 1965) p 67 L. F. Fieser, M. Fieser, Reagents for Organic Synthesis (New York, 1967) pp 61, 183, 185, 190, 519, 720, 722, 723. Review of carbonylations A. Mullen, Carbonylations Catalyzed by Metal Carbonyls-Reppe Reactions in New Syntheses with Carbon Monoxide, J. Falbe, Ed. (Springer-Verlag, Berlin, 1980) pp 243-308. Mechanistic study of cyclooctatetraene synthesis R. E. 

Acetylene-Based Routes. Walter Reppe, the father of modem acetylene chemistry, discovered the reaction of nickel carbonyl with acetylene and water or alcohols to give acryUc acid or esters (75,76). This discovery led to several processes which have been in commercial use. The original Reppe reaction requires a stoichiometric ratio of nickel carbonyl to acetylene. The Rohm and Haas modified or semicatalytic process provides 60—80% of the carbon monoxide from a separate carbon monoxide feed and the remainder from nickel carbonyl (77—78). The reactions for the synthesis of ethyl acrylate are... 

Monosubstituted acetylenes add formaldehyde in the presence of copper, silver, and mercury acetyUde catalysts to give acetylenic alcohols (58) (Reppe reaction). Acetylene itself adds two molecules (see Acetylene-DERIVED chemicals). 

Acetylene is condensed with carbonyl compounds to give a wide variety of products, some of which are the substrates for the preparation of families of derivatives. The most commercially significant reaction is the condensation of acetylene with formaldehyde. The reaction does not proceed well with base catalysis which works well with other carbonyl compounds and it was discovered by Reppe (33) that acetylene under pressure (304 kPa (3 atm), or above) reacts smoothly with formaldehyde at 100°C in the presence of a copper acetyUde complex catalyst. The reaction can be controlled to give either propargyl alcohol or butynediol (see Acetylene-DERIVED chemicals). 2-Butyne-l,4-diol, its hydroxyethyl ethers, and propargyl alcohol are used as corrosion inhibitors. 2,3-Dibromo-2-butene-l,4-diol is used as a flame retardant in polyurethane and other polymer systems (see Bromine compounds Elame retardants). 

Nickel plays a role in the Reppe polymeriza tion of acetylene where nickel salts act as catalysts to form cyclooctatetraene (62) the reduction of nickel haUdes by sodium cyclopentadienide to form nickelocene [1271 -28-9] (63) the synthesis of cyclododecatrienenickel [39330-67-1] (64) and formation from elemental nickel powder and other reagents of nickel(0) complexes that serve as catalysts for oligomerization and hydrocyanation reactions (65). 

Garboxylation Reaction. The carboxylation reaction represents the conversion of acetylene and olefins into carboxyHc acids (qv) or their derivatives. The industrially important Reppe process is used in the synthesis of P-unsaturated esters from acetylene. Nickel carbonyl is the catalyst of choice (134). 

Reaction of coke with calcium oxide gives calcium carbide, which on treatment with water produces acetylene. This was for many years an important starting point for the production of acrylonitrile, vinyl chloride, vinyl acetate and other vinyl monomers. Furthermore, during World War II, Reppe developed routes for many other monomers although these were not viable under normal economic conditions. 

The reaction of amines and acetylene takes a different course in the presence of Zn(OAc)2/Cd(OAc)2. Thus, for example, EtNHj gives N-ethylethylideneamine in moderate yield (Eq. 4.60) [250], not ethylvinylamine as Reppe et al. had reported earlier [251]. 

It is important to mention the pioneering work of Reppe and co-workers who discovered as early as 1938 the industrial preparation of acrylic acid by car-bonylation of acetylene [28]. The reaction was conducted at 200-230 °C and 100 bar of CO and catalyzed by Ni(CO)4 in the presence of a copper halide. Selectivity of 90 and 85% were reached in acrylic acid with regard to acetylene and carbon monoxide, respectively [29]. 

The Reppe process was commercialized in the 1950s. It involves the reaction pf acetylene, carbon monoxide, and an alcohol (methyl, ethyl, etc.) to give an acrylic ester (an acrylate). The process is carried out at 125°F and 15—30 psi in a nickel carbonyl/aqueous hydrochloric acid solution. The nickel carbonyl acts as both a catalyst and a secondary source of carbon monoxide. 

Some acrylates are still produced by a modified Reppe process that involves the reaction of acetylene, the appropriate alcohol (in the case of butyl acrylate, butyl alcohol is used), and carbon monoxide in the presence of an acid. The process is continuous and a small amount of acrylates is made this way. The most economical method of acrylate production is that of the direct oxidation of propylene to acrylic acid, followed by esterification. 

The ability of nickel complexes, e.g., nickel carbonyl and its phosphine derivatives, to catalyze polymerization and other reactions of olefins and acetylenes has been studied extensively (46, 53), particularly by Reppe. 

In the German process for prepn of erythritol (by Reppe), starting materials are acetylene and formaldehyde and reactions can proceed as follows fj... 

Acrylic Acid and Acrylates. Acrylic acid and acrylates may be produced commercially by the Reppe reaction of acetylene.76,184-187 However, the industrial significance of these processes has diminished since acetylene is no longer a viable source and was replaced by ethylene. Acrylic acid and acrylates are now produced by propylene oxidation (see Section 9.5.2). 

REPPE PROCESS. Any of several processes involving reaction of acetylene (1) with formaldehyde to produce 2-butync-l,4-diol which can be converted to butadiene (2) with formaldehyde under different conditions to produce propargyl alcohol and, form this, allyl alcohol (3) with hydrogen cyanide to yield acrylonitrile (4) with alcohols to give vinyl ethers (5) with amines or phenols to give vinyl derivatives (6) with carbon monoxide and alcohols to give esters of acrylic acid (7) by polymerization to produce cyclooctatetraene and (8) with phenols to make resins. The use of catalysis, pressures up to 30 atm, and special techniques to avoid or contain explosions are important factors in these processes. 

Reppe and co-workers reported in 1948 the Ni-catalyzed cyclotetramerization of acetylene to give cyclooctatetraene (106) [58]. After this discovery, the reaction was expanded to monosubstituted alkynes. Monosubstituted alkyne 138 is cyclized smoothly to give tetrasubstituted cyclooctatetraene 139 [59]. Internal alkynes are... 

Nickel catalysts for the syntheses of cyclic compounds were first successfully utilized by Reppe, who was able to prepare cyclooctatetraene from acetylene (65). This eight-membered ring synthesis, and also the preparation of cyclic products from strained olefins (e.g., bicycloheptene and norbornadiene) and acrylonitrile, have been adequately reviewed elsewhere (7) and will therefore not be considered further. A short account of the cyclization reactions of butadiene using nickel-containing catalysts has appeared previously in this series (/). The discovery of new synthetic possibilities and a deeper understanding of the mechanism of these reactions justify a more extensive treatment. 

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