Emil Fischer

Emil Fischer

The German chemist Emil Fischer (1852-1919), perhaps the greatest of the organic chemists, is known for his work in the study of pure sugars and proteins.

Emil Fischer was born at Euskirchen, Prussia, on Oct. 9, 1852. After studying chemistry at the University of Bonn for a short time, he transferred to the University of Strassburg and received a doctoral degree in 1874. Fischer moved to Munich that year and spent 8 productive years there. He then went to Erlangen (1882) and to Würzburg (1885) and finished his career as professor of chemistry at the University of Berlin (1892).

Studies of Pure Sugars

Of the many natural products available for man's use, perhaps no group is so important as the carbohydrates. Until 1884, however, no exact scientific study of the carbohydrates had been undertaken, and little was known concerning their chemical constitution or the arrangement of their molecules. Between 1884 and 1900 Fischer successfully determined the inner structure of the sugar group and thus gave scientists the key to an understanding of other carbohydrates.

Fischer's first step in unraveling the mysteries of the sugar group was the discovery in 1875 of phenyl hydrazine, a compound which could be used as a general reagent for separating and isolating sugars. Through the use of phenyl hydrazine and its derivatives, he discovered the presence in sugars of the carbonyl group (=CO). By 1884 he was able to produce crystalline derivatives with various sugars; hitherto, these derivatives had been available only in impure mixtures which almost always were syrups. Fischer was also able to show that the best-known sugars contain six carbon atoms. Differences in the sugars could be detected through their effects, in solution, on polarized light, although not all of them were found to be optically active.

Fischer synthesized some of the known sugars such as fructose and glucose, and he identified 16 stereoisomeric forms of glucose. In addition, he synthesized a number of sugars that do not occur in nature and demonstrated their structural relationships. His work proved to be a vindication of the asymmetry theory of J. H. van't Hoff and J. A. Le Bel; that is, mirror-image molecules do, in fact, exist.

Purine Group

At approximately the same time that Fischer was involved with the analysis and synthesis of sugars, he accomplished a great deal of research on another important group of compounds, the purine group, or purine derivatives. Among the purine derivatives are caffeine, xanthine, theobromine, and uric acid. The Swedish chemist Carl W. Scheele discovered uric acid in 1776, and Justus von Liebig and Friedrich Wohler studied its derivatives in the 1830s. Adolf von Baeyer was also interested in studies of this natural product of tissue waste and succeeded in presenting an orderly arrangement of the purine derivatives. However, the final determination of the structures of the purine group was done by Fischer during his years at the universities of Erlangen and Würzburg. Later, at Berlin, he synthesized xanthine, caffeine, theobromine, adenine, and the parent compound, purine. Before 1900 Fischer and his students had investigated no fewer than 130 purine derivatives. In 1902 he received the Nobel Prize for his work on sugars and purines.

Research in the Proteins

From his previous research, Fischer was led in 1899 to the study of an even more complex group of natural products, the proteins. The proteins themselves are made up of amino acids; therefore the first steps in his research had to be the investigation of the amino acids, and he proceeded with great skill to isolate and identify them.

The difficulties in these researches were such as to discourage any but the most persistent of investigators, for the proteins are noncrystalline, are sensitive to heat, alcohol, and acids, and cannot easily be produced in a pure state. Fischer's basic method was to prepare the esters of amino acids and then distill them fractionally. Once the amino acids were separated, they could be built up into more complex structures, which he called polypeptides. With this method, the number of possible variations was almost unlimited, and it became evident why such a large number of different proteins exist in nature. In this field of study his greatest achievement was perhaps his synthesis in 1907 of a simple, but real protein molecule.

Later Life and Character

Fischer continued to investigate new areas of organic chemistry. His vacations in the Black Forest of Bavaria led him to study the chemical substances in the lichens that were attached to the old evergreens, and he discovered a new group of compounds, the "depsides." He also studied the constitution and synthesis of tanning substances and initiated some research into the composition of fats.

During World War I Fischer held a position as scientific adviser to the German government, with the task of organizing industrial chemical production for the war effort. He increased the ammonia supply from coke ovens, stimulated the production of the synthetic nitric acid industry, and attempted to organize the production of "synthetic" food. He also worked closely with the German dye industry but never accepted any of the lucrative industrial posts offered to him.

As a professor at Berlin, Fischer found himself called upon for many duties outside teaching and research. He was several times president and vice president of the German Chemical Society and was a member of the Prussian Academy of Sciences. Because of the pressure of these outside activities, he sought to establish private research facilities and to turn over his teaching duties to younger men. In this effort he helped to found the Kaiser Wilhelm Institute for Chemistry and the Kaiser Wilhelm Institute for Carbon Research.

Fischer was a scientist of great talent, imagination, and energy who spent his life in dedication to his field. He married Agnes Gerlach, the daughter of an anatomy professor at Erlangen, in 1885; they had three sons. Agnes Fischer died in 1892.

During the war Fischer suffered from ill health, first from chemical poisoning and then from cancer. He tried unsuccessfully to treat the disease with various chemicals and died on July 15, 1919. One of his colleagues, the Nobel Prize winner Richard Willstätter, said of Fischer's life and character, "He was the unmatched classicist, master of organic-chemical investigation with regard to analysis and synthesis, as a personality a princely man."

Further Reading

A sympathetic biographical essay on Fischer can be found in Burckhardt Helferich's contribution to Eduard Farber, ed., Great Chemists (1961). A brief account of Fischer's work is included in J. R. Partington, A Short History of Chemistry (1937; 3d ed. rev. 1957), and in Alexander Findlay, A Hundred Years of Chemistry (1937; 3d ed. 1965). □