Erlenmeyer, Richard August Carl Emil

(b. Wehen, Germany, 28 June 1825; d. Aschaffenburg, Germany, 22 January 1909)

chemistry.

Erlenmeyer was one of the earliest disciples of Kekule and advocated Kekule’s views on the constitution of organic compounds at a time when many of the leading chemists still adhered to dualistic or to type theories. Erlenmeyer himself was converted from the old chemical types to the newer views on valence and structure. He entered the University of Giessen in 1845 as a medical student, but on hearing Liebig lecture he decided to study chemistry, first at Giessen and then at Heidelberg, where he became one of Kekule’s first private students. He was professor of chemistry at the Munich Polytechnic School from 1868 until his retirement in 1883. In addition to teaching and publishing many research papers, Erlenmeyer was an editor of the Zeitschrft fur Chemie und Pharmazie and of Liebig’s Annalen der Chemie. He was coauthor of the three-volume Lehrbuch der organischen Chemie (1867–1894).

Erlenmeyer published important work in both experimental and theoretical organic chemistry. His researches were mostly in the synthesis and constitution of aliphatic compounds. In 1865 he discovered and synthesized isobutyric acid. He synthesized guanidine in 1868 and gave the first correct structural formulas of guanidine, creatine, and creatinine. He prepared several hydroxy acids and explained the formation and structure of the lactones derived from them in 1880. He synthesized tyrosine in 1883. Erlenmeyer invented the conical flask that bears his name (1861).

Erlenmeyer also dealt with many theoretical problems, and his remarks on valence and structure were fundamental to the development of these new ideas. He introduced the term “Struktuxchemie” as well as the designations “monovalent,” “divalent,” and so on, which he employed in place of “monoatomic” and “diatomic.”

Alexander Crum Brown in 1864 depicted the structures of organic compounds by drawing chemical bonds with dotted lines and enclosing the atomic symbols in circles. Chemists were hesitant to accept and use these graphic representations until Erlenmeyer in 1866 abandoned the old type formulas and adopted the new structural ones. By modifying Crum Brown’s graphic formulas, he introduced the modern structural notation.

Another central problem in the new structural theory concerned the constitution of ethylene and other unsaturated compounds. Crum Brown suggested that their unique feature was the sharing of two valence units by each of two carbon atoms. Erlenmeyer not only adopted the double bond for ethylene but also introduced the triple bond to represent acetylene. His formulas, using lines to represent chemical bonds, proved convincing, and chemists adopted his notation.

Erlenmeyer investigated constitutional problems and proposed structural formulas for many organic substances. He immediately adopted Kekule’s ring structure for benzene and proposed the modern naphthalene formula of two benzene rings with two carbon atoms in common.

In 1880 he formulated what is known as the Erlenmeyer rule: All alcohols in which the hydroxyl group is attached directly to a double-bonded carbon atom become aldehydes or ketones. He had attempted to prepare such alcohols but obtained the isomeric carbonyl compounds in every case. Erlenmeyer concluded that such alcohols were incapable of existence, being converted at the instant of their formation into aldehydes or ketones by an intramolecular rearrangement.

BIBLIOGRAPHY

Erlenmeyer, with others, wrote the Lehrbuch der organischen Chemie, 3 vols. (Leipzig-Heidelberg, 1867–1894). He also wrote a small treatise, Uber den Einfluss des Freiherm J. von Liebig auf die Entwicklung der reinen Chemie (Munich, 1874), as a tribute to Liebig. His new graphic formulas, the triple bond, and the naphthalene structure are found in his “Studien öber die s.g. aromatischen Sauren,” in Annalen der Chemie, 137 (1866), 327–359; his rule on vinyl alcohols is in “Öber Phenylbrommilchsäure,” in Berichie der Deutschen chemischen Gesellschaft, 13 (1880), 305–310. There is a BIBLIOGRAPHY of his papers with a detailed account of his life and work by M. Conrad, ibid., 43 (1910), 3645–3664.

William Henry Perkin wrote an interesting brief account of Erlenmeyer’s work in Journal of the Chemical Society, 99 (1911), 1649–1651.

Albert B. Costa