Otto Wallach was a highly regarded professor of chemistry whose curiosity about essential oils led to research that benefited both organic chemistry and an important industry. For his meticulous procedures and initiative in the study of terpenes, a class of compounds he identified and named as essential oils, Wallach received the Nobel Prize in chemistry in 1910. Essential oils, called ethereal oils in Wallach's time, are fragrant extracts from plant materials that are used in perfumes, flavorings, and medicines. Terpenes are responsible for much of the pleasant odor associated with essential oils. Wallach's work provided a scientific foundation for the fragrance industry.
Otto Wallach was born on March 27, 1847, in Königsberg, in East Prussia (Königsberg is now called Kaliningrad and is part of the reorganized former Soviet Union). Wallach's mother was Otillia Thoma Wallach; his father, Gerhard Wallach, was an official in the Prussian government whose post necessitated moves from Königsberg to Stettin (now in Poland and called Szczecin) and then to Potsdam, near Berlin, Germany. Wallach graduated from the Potsdam Gymnasium (high school). In school he became fascinated with chemistry and the history of art, and pursued both interests throughout his life. Early in 1867 he entered the University of Göttingen and received his doctorate in chemistry in 1869. Wallach never married.
Wallach's doctoral dissertation was on isomers of toluene. Isomers ( iso means same; mer means parts) are substances with identical composition, but different arrangements of the parts, giving the substances different physical and chemical properties. Toluene is one of the products of distillation of coal, and among its many uses is as a solvent in the preparation of fragrances. Wallach's doctoral studies were to provide the background for his most important research.
After graduation Wallach worked briefly in Berlin, then went to the University of Bonn to assist August Kekulé (1829-1896), a renowned German professor of chemistry whose most noted contribution was the discovery of the structural formula of benzene, another important coal product and a substance similar to toluene. Kekulé was interested in turning much of his laboratory work over to a young assistant. Wallach remained at the University of Bonn until 1889, except for a period of two years, from 1871 to 1873, when he tried research at Aktiengesellschaft für Anilinfabrikation (Agfa).
In 1879, as a professor at the University of Bonn, Wallach was assigned to teach pharmacy. He had little background in the chemistry of essential (ethereal) oils, used in medicines. In Kekulé's laboratory he found abandoned samples of essential oils that Kekulé thought were too complex even to attempt to analyze. A very patient researcher, Wallach distilled and redistilled each oil sample until he could identify a pure substance. By 1881 he had repeated his procedure with different oils and identified eight pure, very similar, fragrant substances that he named terpenes, from the Greek terebinthos meaning turpentine.
Wallach did not work alone. While some colleagues worked on synthesizing new and similar compounds, he devoted most of his effort to studying how the terpenes he separated from essential oils were related. By 1887 Wallach discovered that all the terpenes he identified in essential oils are derived from a multiple of a particular arrangement of five carbon atoms, now called isoprene units . Some examples of terpenes found naturally are bayberry, rose oil, peppermint, menthol, camphor, and turpentine.
In 1889 Wallach was appointed director of the Chemical Institute at the University of Göttingen, where he continued his work on terpenes. In 1910 he received the Nobel Prize in chemistry "for his initiative work in the field of alicyclic substances," the terpenes, discovered to have carbon atoms arranged in rings, or cycles. Kekulé was the first person to identify a compound (benzene) as shaped like a ring.
One of the most important outcomes of Wallach's work was the research it spawned, which, combined with his own work, forever changed the fragrance industry. Before Wallach, there was little scientific background for production of fragrances. Processes used were much like the ones brought to Europe by the Crusaders. Wallach described the change his work inspired in his Nobel address. "The fragrant components of plants were merely distilled and the distillate brought to market. In this process, the products obtained were not always handled rationally, in the absence of all knowledge of their chemical nature, and the doors were wide open for every kind of falsification. When this was carried out with only some skill, the consumer was helpless against it.
"This has now been changed thoroughly. Thanks to the possibility of distinctly characterizing single components of the ethereal oils, we now possess a significant analytical system to detect falsifications and to guard against them." Wallach's work, combined with the work of others he inspired, was credited with putting science into the production of perfumes, flavorings, and medicines that use terpenes.
Many universities and scientific societies honored Wallach. In 1912 he received the Davy Medal, awarded to outstanding scientists in memory of the British chemist, Sir Humphrey Davy (1778-1829), who identified a number of chemical elements through his pioneering work with electrochemistry. Wallach retired from Göttingen in 1915, but continued with research until he was eighty years old. In his lifetime Wallach published 126 papers on his research of essential oils. He died in Göttingen, Germany, on February 26, 1931, a month short of his eighty-fourth birthday.
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