REPPE, JULIUS WALTER

(b. Göringen, Germany, 29 July 1892; d. Heidelberg, Germany, 27 July 1969), industrial chemistry, polymer synthesis, acetylene chemistry, ethylene chemistry.

Reppe was one of the finest industrial chemists of the interwar period. He carried out hazardous research on the reactions of acetylene (ethyne) under pressure and thereby opened up entirely new fields of industrial organic chemistry. Numerous industrial processes have resulted from his work, including acrylic acid (propenoic acid) and 1,4-butynediol from acetylene, propionic acid (propanoic acid) from ethylene (ethene), and acetic acid (ethanoic acid) from methanol; he is also well-known for his remarkable synthesis of cyclooctatetraene. These new areas were soon called “Reppe chemistry.” He also developed several polymers, including substitutes for chewing gum and human blood plasma.

After World War II, Reppe was described as making a larger contribution to chemistry than any other employee of the large German chemical firm I. G. Farben. The project to transfer leading German scientists to the United States (Project Paperclip) ranked Reppe as highly as the discoverer of nuclear fission, Otto Hahn. Yet for all his scientific achievements, Reppe never won the Nobel Prize. This was partly the result of bias against industrial chemists (a prejudice that would have been incomprehensible to Reppe’s fellow industrial chemist, Alfred Nobel) and partly because of Reppe’s research at I. G. Farben, which was closely linked to the Nazi regime in Germany.

Despite his hopes, Reppe’s industrial processes never became the basis for the entire organic chemical industry. In the 1950s acetylene was replaced as a major raw material for the chemical industry by cheaper, petroleum-based starting materials, and new processes were developed that made Reppe’s work in certain key areas obsolescent. After the Americans failed to persuade him to relocate to the United States after World War II, he was permitted to become research director at BASF, created out of the former I. G. Farben. In that capacity he was a participant in the shift from coal to petroleum, which was spearheaded in Germany by BASF; he had been one the pioneers of ethylene chemistry in the mid-1920s.

Childhood and Early Career Walter Reppe was born in Göringen, near Eisenach, in Thuringia, Germany, on 29 July 1892, the son of Rudolf Reppe, a schoolteacher, and his wife, Maria Reppe (née Schröder). He went to school in Apolda and Weimar. Reppe studied chemistry at the University of Jena and the University of Munich before serving in the artillery during the World War I. After being wounded three times, he was commissioned as a lieutenant in the reserve in February 1917 and moved from the front line. After the war Reppe returned to the University of Munich where he took his PhD in 1920 on the reduction of aryl derivatives of nitric acid, working under Professor Kurt H. O. Meyer. After a short spell as an assistant to Meyer at the University of Munich, Reppe joined BASF at Ludwigshafen in the Palatinate in 1921. This move was clearly a result of Meyer’s impending appointment as the head of BASF’s main research laboratory. Reppe’s first year at Ludwigshafen was spent in the Hauptlaboratium (Central Research Laboratory) and his second year in the indigo laboratory. Between 1924 and 1933 he carried out research in the new solvents laboratory, but he also helped to manage the industrial plant and carried out the development of processes to the industrial scale. This combination of research, development, and factory management was quite normal in the German chemical industry at this time. Reppe’s company, BASF, merged with the other major firms in the German dyestuffs industry—Bayer, Hoechst, Griesheim, and Agfa—in 1925 to form a large combine, I. G. Farbenindustrie AG, headed by Carl Bosch, developer of the Haber-Bosch ammonia process, and the former chairman of BASF. The Ludwigshafen works became part of the Oberrhein Betriebsgemeinschaft (Upper Rhine works community), but life at the factory level continued much as before.

Reppe’s first major project was the industrial synthesis of butyl alcohol (butanol) from acetylene, under the direction of Curt Schumann and Gerhard Steimmig. This effort was linked to the soaring popularity of the automobile, particularly in the United States but also in Germany, where the number of automobiles rose from 4,600 in 1908 to 39,000 in 1925. This growth created a huge demand for several organic chemicals, including butyl alcohol, which was a solvent for the lacquers used to paint automobiles. By 1929 the United States produced nearly 23,000 metric tonnes of butyl alcohol by the fermentation of maize and from petroleum. Fermentation was out of the question, as food was increasingly scarce in Germany, which also lacked any major oil or gas fields. The well-known aldol reaction, which converts acetaldehyde (ethanal) to aldol (3-hydroxybutanal), offered an attractive alternative. The acetaldehyde was made from acetylene and the aldol was easily reduced to butyl alcohol. This process later became the core of I. G. Farben’s route to butadiene, a key building block of synthetic rubber.

After the butyl alcohol research was successfully completed, Reppe worked on the manufacture of ethylene oxide. This too was connected with the rise of the automobile and in particular the need to add an antifreeze to the coolant water. The earliest antifreezes were natural glycerol (1,2,3-propanetriol) and methanol, still obtained in America from wood distillation in this period. However, glycerol was replaced by the superior ethylene glycol (1,2-ethanediol), marketed by Union Carbide as Prestone in 1927. Ethylene glycol—one of the first major petrochemical products—was a problematic product for I. G. Farben, as it did not have an Abūndant source of ethylene apart from expensive fermentation-based ethyl alcohol (ethanol). Even so, the growing demand for antifreeze and the fear of competition from Union Carbide compelled I.G. Farben to develop its own route to ethylene glycol between 1926 and 1928. Ethylene, initially from natural ethyl alcohol and subsequently extracted from coal gas, was reacted with chlorine and water to produced ethylene chlorohydrin (2-chloroethanol), which was then made into ethylene glycol. Glysantin, the German response to Prestone, was launched in the cold winter of 1928–1929. In the course of this research, Reppe discovered a new catalyst for the conversion of ethyl alcohol to ethylene and developed a continuous process for the manufacture of ethylene chlorohydrin.

Research on Butadiene The increasing demand for rubber created by the automobile, and the attempt by the British government to push up the price of natural rubber by limiting exports from Malaya, encouraged I. G. Farben to resume the synthesis of rubber. An early form of synthetic rubber called methyl rubber (polymethylisoprene) had been developed by Bayer and BASF before World War I, but its manufacture had been abandoned after the end of World War I in November 1918. By this time most chemists agreed that butadiene was the best building block for an economically viable synthetic rubber, as it is cheaper to make than isoprene, the building block of natural rubber. And in I. G. Farben, acetylene was the obvious starting material for butadiene, beginning with the addition of water to acetylene to form acetaldehyde.

The butyl alcohol synthesis of BASF provided the basis for the two middle steps, the conversion of acetaldehyde to aldol and its reduction to 1,3 butylene glycol (1,3-butanediol). This much was clear, but none of the existing catalysts could remove the elements of water from the glycol to make butadiene without producing other unwanted by-products. In 1927 Reppe and Ulrich Hoffmann, his colleague in the solvent laboratory, discovered that sodium hydrogen phosphate was a good catalyst for this dehydration reaction, and they soon improved it by adding a little phosphoric acid. This catalyst paved the way for the industrial production of butadiene (the so-called four-step process, Vierstufenverfahren in German), which was later used to make Buna S synthetic rubber, a copolymer of butadiene and styrene invented in 1929 by chemists in I. G. Farben’s laboratories in Leverkusen, near Cologne.

Beginning of Reppe Chemistry When his work on the dehydration of butylene glycol was completed in 1928, Reppe was given the task of finding an industrial process for making vinyl ethers. The polymers of these ethers were regarded as possible alternatives to the hitherto troublesome polyvinyl chloride (PVC), which at that time had a tendency to decompose when worked on hot rollers. The few known routes to vinyl ethers were found to be unsuitable or not to work at all, and Reppe was forced to devise a new synthesis. He discovered that vinyl chloride reacted with sodium ethoxide to form the desired ethyl vinyl ether with very little of the expected (but unwanted) byproduct acetylene. Further research revealed that the acetylene formed in the initial reaction was combining with ethyl alcohol under the pressure in the autoclave, and that the sodium ethoxide was acting as a catalyst. When Reppe first tried the reaction between acetylene and ethyl alcohol at 15 atmospheres, he expected an explosion to occur at any moment, as acetylene is very unstable under pressure. As he said in his idiosyncratic English in his report written for the Allies after World War II, “our tension was tops.” To use the reaction on the industrial scale, I. G. Farben had to ignore government regulations about the use of acetylene under pressure introduced for the protection of welders. The polyvinyl ethers were not as widely applicable as at first hoped and subsequent improvements in the stability of PVC removed the driving force for the development of these polymers as a substitute for PVC. Nonetheless, the polyvinyl ethers were used for a variety of purposes including adhesives, lacquers, and waxes. During World War II, polyvinyl ethers and polyvinyl amines served as very useful substitutes for chewing gum, human blood plasma, and mica.

The early 1930s saw major changes in the management of research at Ludwigshafen. The Hauptlaboratium was badly hit by the Great Depression, although the number of chemists working was maintained. Meyer left in January 1932, apparently because of disagreements with the main board of directors. Hermann Mark followed in September, and in his case the worsening political situation (Mark was half-Jewish) was at least part of the reason, although he too may have had policy differences with the firm’s leaders. Reppe’s outstanding research on butadiene and vinyl ethers was rewarded by his appointment as the head of the intermediates and plastics laboratory at the beginning of 1934. This new laboratory spearheaded the research on the production of synthetic materials at Ludwigshafen and in particular the scaling up of the production of vinyl ethers. I. G. Farben was also doubtlessly attempting to regain some of its momentum in the plastics field, which had been lost with the departure of Meyer and Mark. This promotion also brought Reppe into closer contact with Otto Ambros, a fellow graduate of the University of Munich and a rising star within I. G. Farben who was in charge of the development of organic chemicals at Ludwigshafen and who worked on the planning of the synthetic rubber program under I. G. Farben’s powerful technical director, Fritz ter Meer.

The Ethynylation Reaction The Nazis seized power in 1933 and the new National Socialist regime’s desire for self-sufficiency revitalized the synthetic rubber project. Reppe was involved in the search for a better route to butadiene than the four-stage process. The long-desired breakthrough came in September 1937, when Reppe discovered the so-called ethynylation reaction. The most important example of ethynylation was the addition of two molecules of formaldehyde (methanal) to acetylene, under pressure, to form 2-butyne-1,4-diol. If the use of acetylene under pressure was not worrying enough, the catalyst used in this reaction, copper acetylide, had hitherto only been used as a detonator for dynamite. Reppe had in fact originally tried to use inorganic copper salts as catalysts, presumably drawing an analogy with Julius Nieuwland’s process for the dimerization of acetylene, a reaction that been intensively investigated elsewhere in I. G. Farben but which was abandoned after two chemists were killed in an explosion. Aware of the dangers of copper acetylide, Reppe took great care to prevent its formation in his experiments. Only after nine months of continuous failure did he suddenly realize that copper acetylide was actually acting as a catalyst.

This ethynylation reaction became the basis of the Reppe process for butadiene, which used only one molecule of expensive acetylene rather than the two consumed by the four-step process. After the initial teething problems were solved, the Reppe process was used to make synthetic rubber at Ludwigshafen in 1943–1944. The operation of a high-pressure acetylene plant that employed a percussive compound as a catalyst in the midst of aerial bombardment was a feat of technical skill and great courage. The sides of the butynediol building were left open to reduce the debris caused by any explosion. After the war, Allied investigators were astounded that the Germans had even considered using this reaction on a large scale. A group of Imperial Chemical Industries (ICI) chemists had made four pounds of butynediol in the early years of the war using Reppe’s reaction, and they had naively imagined that they had made the largest-ever batch of this compound. By contrast, Ludwigshafen had produced 30,000 metric tonnes in 1944. Reppe energetically developed new end uses for butynediol in the laboratory, but his intricate pathways to products such as nylon 66 found little favor outside Ludwigshafen.

Carboylation and Cyclooctatetraene Reppe was once again rewarded for his success with a promotion at the beginning of 1938 to become head of the Hauptlaboratium at Ludwigshafen, the position once held by his old PhD supervisor, Kurt Meyer. But Reppe’s view of research was very different from that of Meyer, with Reppe focusing on technical developments of use to I. G. Farben and the German state rather than broadly based basic research with an international outlook. This was largely a result of the times—the National Socialist Four Year Plan to create a self-sufficient Germany was at its height—and also a reflection of Reppe’s desire to use highly novel chemical reactions to produce valuable products.

Leaving the scaling up of the ethynylation process to his colleagues, notably Georg Niemann and Franz Reich-eneder, Reppe now turned to the reaction between carbon monoxide and acetylene in the presence of alcohols to form acrylate esters. The polymers of the acrylate esters (and the related polymethacrylates) were (and still are) an important group of plastics. Reppe attempted to use nickel carbonyl as the original catalyst, but it was converted during the reaction to a nickel halide. This problem was eventually solved by using the nickel halide (usually the bromide) as the catalyst; it forms a transient carbonyl compound with carbon monoxide under the conditions of the reaction. While this method of making acrylates was very useful, it suffered from a number of problems— mainly to do with the catalyst—at the pilot plant stages, problems that remained largely unsolved in 1945. Reppe also used nickel carbonyl to add carbon monoxide to methanol to produce acetic acid. This reaction also had problems at the pilot plant stage, and the full-scale plant only came onstream in 1957.

Meanwhile, in the spring of 1940, Reppe became aware of Otto Roehlen’s research at Ruhrchemie in Oberhausen on his so-called OXO process, which combined olefins with carbon monoxide to form aldehydes, which were converted into the corresponding alcohols (used, for example, to make detergents). This work was a spin-off of Ruhrchemie’s development of the Fischer-Tropsch process for synthetic fuel. During World War II, Reppe and his colleague Hugo Kröper used his carbonylation reaction to make propionic acid from ethylene. Unfortunately, this process suffered greatly from corrosion problems, and a silver-lined reaction vessel had to be used in 1943. Partly because of the French occupation after the war, the full-scale plant was not ready until 1951.

In December 1940 Reppe’s colleague, Tim Toepel, tried to make 3-hexyne-1,6-diol by adding ethylene oxide to acetylene using nickel cyanide as a catalyst, presumably with the aim of preparing the monomers of nylon 66 from acetylene. This was unsuccessful but, quite unexpectedly, a mixture of cyclic hydrocarbons was formed. Further investigation revealed that the major product was cyclooctatetraene (COT), a cyclic compound that was at the heart of scientific investigations into the basis of aromaticity. Despite the difficulties created by wartime conditions, particularly air raids and lack of trained staff, Reppe and his group carried out an extensive amount of fundamental research on COT during the war. In 1948 they published their findings, which formed the basis for later academic research on this interesting compound However, Reppe’s hopes for industrial end uses for COT have turned out to be ill-founded, partly because acetylene has become too expensive and partly because it has been displaced by the related oligomerization of butadiene patented by Günther Wilke at the Max-Planck-Institut für Kohlenforschung (Max Planck Institute for Coal Research) at Mülheim in the Ruhr in 1956.

The End of I. G. Farben It has to be emphasised that most of Reppe’s processes had not left the laboratory, or at best had reached the pilot plant stage, by 1945. Only the vinyl ethers and the Reppe process (for butadiene) had been transferred to the industrial scale. The chemicals produced of the new Reppe chemistry accounted for a trivial 2.5 percent of all acetylene-based chemicals in Germany in 1943. As Allied bombs rained down on the large chemical complex at Ludwigshafen, Ambros moved on 21 September 1944 to Gendorf—a small factory east of Munich, near the Austrian border—that made ethylene diglycol for explosives. This evacuation was linked to a vain attempt to move synthetic rubber production from Ludwigshafen to an underground factory nearby. Reppe was also transferred to Gendorf with most of his laboratory. He installed himself in one of the factory buildings and attempted to resume his research on chemical reactions under pressure.

On 6 May 1945 the U.S. Army entered Gendorf and encountered Ambros and Reppe. At first they were allowed to remain at Gendorf, but on 10 June they were taken into custody so that they could be interrogated about their work at I. G. Farben, especially the production of nerve gases (with which Reppe had never had any connection). On 6 July the American Chemical Society suggested that Reppe should be questioned about his work on acetylene, and eight days later Reppe was taken to Dustbin, the Allied detention center—at Schloss Kransberg, Hermann Goering’s former castle northeast of Frankfurt—run by the British. Reppe insisted he needed more freedom and access to his files if he were to be able to write a report on his pioneering research. He was released from Dustbin in October 1945 into the custody of Lieutenant Colonel Maurice Bigelow of the U.S. Chemical Corps.

For the next five months Reppe worked on his report in the Frankfurt area under the supervision of Bigelow, but after he turned down a contract to work for the U.S. War Department and became uncooperative, he was returned to Dustbin, remaining there from March to November 1946. He was then moved to Nürnberg (possibly with a view to putting him on trial with the board directors of I. G. Farben); to Ludwigsburg; and in the spring of 1947, to Dachau. Reppe was released from Dachau on 5 June 1947 after almost two years in Allied custody. Bigelow claimed in 1949 that it had been necessary to keep Reppe in custody to prevent him being forced to work in a road gang as a former Nazi Party member. The Americans had probably also hoped that this imprisonment would make Reppe eager to go to America, as he was one of the top targets for Project Paperclip. During this period, teams of Allied investigators assiduously gathered documents about Reppe chemistry that they found in I. G. Farben’s works and interviewed his colleagues. This was only a small part of a massive effort to collect all possible technical information about German industry and military technology. Reppe chemistry, however, was near the top of the list, alongside rocket technology and chemical warfare. Asked by the U.S. Chemical Corps (on behalf of the American Chemical Society) to write a brief popular report for the layperson on his new chemistry, Reppe—rather unwillingly—wrote a long, sometimes rambling account that was highly technical and not at all suitable for the layperson—but which provided the raw material for most contemporary accounts of Reppe chemistry, even Reppe’s own publications.

As soon as the war ended, the Allies dissolved I. G. Farbenindustrie, and its component units came under the control of the occupying power. Ludwigshafen was in the French zone of occupation and came under French control. In 1952, after considerable negotiation, the Western Allies agreed that three successor firms should be set up to take over the former I. G. Farben works in West Germany. Ludwigshafen, along with the neighboring Oppau works, became the nucleus of the new BASF, which considered itself to be the successor of the pre-1925 firm. Meanwhile, the board of directors of I. G. Farben (the Vorstand) had faced an American military tribunal at Nürnberg in 1948, charged with war crimes, although the resulting sentences were relatively light and were commuted in 1950.

Research Director at BASF On his return to Ludwigshafen in September 1947, Reppe worked hard to bring the Hauptlaboratium back to its prewar peak. He also fought successfully to prevent the dismantlement of the synthetic rubber plant at Ludwigshafen so that the production of butyndiol could continue. In 1949 Reppe became head of research at BASF while also remaining head of the Hauptlaboratium. When the new company was given legal standing in 1952, he joined the management board of directors. In the 1950s he supervised the transfer of his carbonylation chemistry to the industrial scale and struggled with the corrosion problems. The acetic acid plant came onstream in 1957 and the proprionic acid plant followed two years later. By contrast, the pilot plant for the production of acrylic acid was not replaced by a full-scale plant until 1965. Reppe developed a new way of making butyl alcohol by reacting propylene (propene) with carbon monoxide and hydrogen, using special catalysts to ensure that only the desired n-butyl alcohol was produced. This was the culmination of his early research on butyl alcohol in the solvents laboratory.

General Aniline and Film Corporation (GAF) pioneered the transfer of Reppe chemistry to the United States. GAF was the successor of the I. G. Farben’s American subsidiaries, and as such, it held the U.S. patents on Reppe’s reactions. One of its chemists, John W. Copenhaver, was a member of the intelligence team that investigated Reppe chemistry after the war. In 1949 he coauthored, with Maurice H. Bigelow, an excellent monograph on Reppe’s work titled Acetylene and Carbon Monoxide Chemistry. GAF’s butyndiol plant at Calvert City, Kentucky, came onstream in 1956, followed by a later plant at Texas City, Texas. By the 1970s the Reppe process was also used by du Pont in Houston, Texas, and BASF-Wyandotte in Geismar, Louisiana.

After his retirement in 1957, Reppe continued to carry out research in his private laboratory. He became interested in vitamin chemistry and was also eager to find a way of making formaldehyde by combining carbon monoxide with hydrogen, but was not successful. He was also a member of the supervisory board of BASF until 1966. Reppe died in Heidelberg on 27 July 1969, two days short of his seventy-seventh birthday.

The Reppe process for butyndiol is still is use in Germany and the United States. It is mainly employed to produce the solvent tetrahydrofuran and in the manufacture of polyurethanes, a new type of plastics that was developed by Otto Bayer, Walter Reppe’s counterpart at I. G. Farben’s laboratory at Leverkusen, near Cologne. In the 1960s and 1970s, COT was widely used in academic research and was the starting point for several important laboratory syntheses, including cyclobutadiene and bull-valene. Interest in COT declined after BASF withdrew free supplies of it in the early 1970s. The BASF pilot plant was closed in 1988, and COT is no longer the subject of intensive research.

Reppe had a rather outspoken personality and was not known for his social skills. He could also be imprudent, a trait that led to the development of Reppe chemistry but that also had its drawbacks. On one occasion in the early 1950s, he was showing some important Japanese visitors around the laboratory when he threw the stub of his cigar—he was a dedicated cigar smoker—into a sink. As the sink contained traces of flammable solvents, a large flame shot up in front of the shocked visitors, and smoking was subsequently banned in BASF’s laboratories. This combination of frankness and recklessness doubtlessly hindered his movement up the corporate ladder, especially in the late 1930s, when diplomatic skills were at a premium when dealing with the Nazi hierarchy. Reppe felt keenly his lack of advancement and honors, at least in 1945. In his I. G. Farben days, Reppe did not travel abroad—international relations were handled by ter Meer and Ambros. However, when Reppe was head of research at BASF in the 1950s, he made successful trips to Spain and Japan in 1953 and to the United States in the following year. This was a sign of the new firm’s international outlook and its desire to forge technological alliances with foreign firms and academics.

It was Reppe’s misfortune that he was at the peak of his powers during the Depression and then the Third Reich, which prevented him from continuing his promising early work on ethylene and forced him to concentrate on acetylene-based strategic materials. His links with the Third Reich probably cost him the Nobel Prize that he richly deserved for his courageous research and his path-breaking acetylene chemistry. Although in the early twenty-first century it may appear to be a representative of a bygone era that used coal and sought economic self-sufficiency, his prewar research and his postwar leadership of research at BASF played an important role in the postwar reconstruction of the West German chemical industry.

BIBLIOGRAPHY

WORKS BY REPPE

With O. Schichting, K. Klager, and T. Toepel, “Cyclisierende Polymerisation von Acetylen I: Über Cyclooctatetraen.” Justus Liebigs Annalen der Chemie 560 (1948): 1–116.

Neue Entwicklungen auf dem Gebiet der Chemie des Acetylens und Kohlenoxyds. Berlin: Springer, 1949. A good overview of Reppe’s research based on his report for the Allied investigators, but less informative than the book by Copenhaver and Bigelow (see Other Sources) based on the same report.

Chemie und Technik der Acetylen-Druck-Reactionen. Expanded ed.Weinheim, Germany: Verlag Chemie, 1952.

“Carbonylierung I: Über die Umsetzung von Acetylen mit Kohlenoxyd und Verbindungen mit reaktionsfähigen Wasserstoffatomen.” Annalen 582 (1953): 1–161.

Polyvinylpyrrolidon. Weinheim, Germany: Verlag Chemie, 1954.

With others. Annalen 596 (1955): 1–224 (ethynylation); Annalen 601 (1956): 81–138 (vinylation).

OTHER SOURCES

Abelshauser, Werner, Wolfgang von Hippel, Jeffrey Allan Johnson, et al. German Industry and Global Enterprise: BASF—The History of a Company. New York: Cambridge University Press, 2004. A history of Reppe’s company that puts his career into its corporate context but which surprisingly has little to say about Reppe (and even less about Reppe chemistry).

Baptista, Robert J., and Anthony S. Travis. “I. G. Farben in America: The Technologies of General Aniline & Film.” History and Technology22, no. 2 (June 2006): 187–224.

Copenhaver, John W., and Maurice H. Bigelow. Acetylene and Carbon Monoxide Chemistry. New York: Reinhold, 1949. The best account of Reppe’s research up to 1945, with an often-elegant translation of Reppe’s own report.

Hummel, Hans Georg. “Walter Reppe.” Chemische Berichte 117 (1984): i–xxii. Concentrates on Reppe’s chemical achievements.

Morris, Peter J. T. “The Technology-Science Interaction: Walter Reppe and Cyclooctatetraene Chemistry.” British Journal for the History of Science 25 (1992): 145–167. Places Reppe’s research on COT in the context of the history of COT chemistry and the study of aromaticity.

———. “Ambros, Reppe, and the Emergence of Heavy Organic Chemicals in Germany, 1925–1945.” In Determinants in the Evolution of the European Chemical Industry, 1900–1939: New Technologies, Political Frameworks, Markets, and Companies, edited by Anthony S. Travis, Harm G. Schröter, Ernst Homburg, et al. Dordrecht, Netherlands: Kluwer, 1998. Explores the relationship between Reppe’s research and the development of synthetic rubber during the Third Reich.

Stokes, Raymond G. Opting for Oil: The Political Economy of Technological Change in the West German Chemical Industry, 1945–1961. Cambridge, U.K.: Cambridge University Press, 1994. Places Reppe’s research in the political and corporate context of the post-1945 rebuilding of the West German chemical industry.

Peter J. T. Morris